No heat from heater 1990 ZR1

[jrd1990zr1]

Thoughts and suggestions please. AC works fine, no codes set, no fuses blown. I only get cold air from heater. Temp gauge never goes above half way. Had heat last fall, but not now. Does this sound like the heater core is air locked? Any thoughts and/or possible fixes are appreciated.

Thanks:handshak:

[-=Jeff=-]

Have you checked coolant level? When was the T-Stat last changed?

if the car is not getting warm and the temp is showing cool, maybe the t-stat is stuck open

[jrd1990zr1]

Jeff,

Coolant was a little low but not much. Not sure about the T-stat, I have not changed it.

Is it possible the coolant went low and I got an air bubble in the heater core?

Thanks, John:handshak:

[-=Jeff=-]

possible, but I have a feeling it is either stuck T-Stat or maybe a clogged heater core

[QB93Z]

You can check the coolant flow to and from the heater core with a thermometer on the pipes in the right side of the engine bay.


The problem could also be a stuck Heater Blend Door. The Heater Blend Door is located between the heater core and the AC Evaporator in the AC Ventilation assembly. It is above the passenger side, lower dash panel.

You can see the Heater Blend Door by removing the AC Blower Control Module from the Ventilation duct in the engine bay, near the firewall, inboard of the coolant expansion tank.

With an assistant you can observe the operation of the Heater Blend Door by removing the AC Blower Control Module and looking in the hole with a flashlight. Turn the Ignition ON. Have your assistant change the AC/Heater thermostat on the dash from 60 degrees to 80 degrees then back to 60 degrees. The door should move. The engine does not need to be running to do this check.


Good luck,


Jim

[jrd1990zr1]

Jim,

I see no movement of a door through the heater resistor hole. Top line to heater core is about the same as the metal crossover, however the return(lower) metal line from the heater core is significantly cooler.

I don't see anything in the 1990 FSM about getting to the door, door actuator or motor. Have you done this on your car? Am I missing something in the FSM?

Thanks again, John :cheers:

[-=Jeff=-]

If I recall, the blend door motor might be Accessible by removing the glove box and glove box door. I know I can see the manual assembly from there.

I forgot about the Electronic blend door.. I have Manual AC which on my 90 I prefer

[BigJohn]

Glove box???

[-=Jeff=-]

A glove compartment or glovebox or glovie is a compartment built into the dashboard, located over the front-seat passenger's footwell in an automobile, often used for miscellaneous storage. The name derives from the original purpose of the compartment, to store gloves. They were sometimes in a box on the floorboard near the driver, hence the alternate moniker of a "glovebox". In most vehicles, the glove compartment closes with a latch, with the option of being locked with a key (often desirable when using valet service, or when parking while the convertible top is down, or when the compartment contains a mechanism to open the trunk).





Yes those of us with 90-93 cars had that privilege of a glove box..

[-=Jeff=-]

BigJohn..

here is a picture to help you
https://www.corvsport.com/wp-content/uploads/2017/02/6065-Dash.jpg

[Mystic ZR-1]

Yep, I see the glove compartment lid doesn't
fit well on your car either...
Typical GM quality.
Never seen one that's right.

[-=Jeff=-]

Yep, I see the glove compartment lid doesn't
fit well on your car either...
Typical GM quality.
Never seen one that's right.

picture is not my car, but mine is the same way

[jrd1990zr1]

Yep, I see the glove compartment lid doesn't
fit well on your car either...
Typical GM quality.
Never seen one that's right.

So Doug have you ever pulled the glove box to get the the heater box?? Before I start ripping and tearing thought I would ask. How was Carlisle, wish I had gone.

John

[-=Jeff=-]

glove box is 9 screws I think.. Pretty simple

[QB93Z]

Jim,

I see no movement of a door through the heater resistor hole. Top line to heater core is about the same as the metal crossover, however the return(lower) metal line from the heater core is significantly cooler.

I don't see anything in the 1990 FSM about getting to the door, door actuator or motor. Have you done this on your car? Am I missing something in the FSM?

Thanks again, John :cheers:

No Movement of the Blend Door is a good indicator of a problem. I did a repair (replace) to my Blend Door Motor on a 1994 ZR-1 which does not have a glove box and the blend door motor is on the bottom of the AC Duct.

The operation and diagnosis of the HVAC controls is (in the 1994 FSM) described in bits and pieces in Volume 1 and in Volume 2 and it takes a fair amount of research to figure it all out.

Here is the Thread where I fixed my problem which may be similar to yours>

http://www.zr1.net/forum/showthread.php?t=27542

Jim

[BigJohn]

BigJohn..

here is a picture to help you
https://www.corvsport.com/wp-content/uploads/2017/02/6065-Dash.jpg

Cool Beans!
I have storage in both doors so the passenger could have their own gloves storage!
There is also a box behind the passenger seat!

:-D

[-=Jeff=-]

As years progressed we got less space

First years (PRE-ABS) 2 full depth storage bins behind seats
my 90 is full depth right and little tray on left

I also have 94 panels so I have the glove bx AND the door storage

[QB93Z]

John,


The Blend Door is controlled by a small electric motor and uses an electronic circuit to send position feed back to the AC Programmer. When the car is first turned ON, the AC Programmer sends a sequential full heat and full cool command to the Blend Door Motor. Since you are not seeing the movement, either the motor has failed, the AC Programmer has failed, there is a wiring problem, or the door is stuck.


I haven't investigated the access to the motor on a 1990 yet, but when you get to it, you can remove it and observe it's operation not connected to the door. And you can try to move the door by turning the pivot rod.


I have a complete set of the duct work from a 1991. I did not see it in the car so I don't know exactly how much you have to take apart to get to the motor.


If you need trouble shooting help when you get to the motor, call me. I will be glad to help.


Jim
443-244-1347

[jrd1990zr1]

John,


The Blend Door is controlled by a small electric motor and uses an electronic circuit to send position feed back to the AC Programmer. When the car is first turned ON, the AC Programmer sends a sequential full heat and full cool command to the Blend Door Motor. Since you are not seeing the movement, either the motor has failed, the AC Programmer has failed, there is a wiring problem, or the door is stuck.


I haven't investigated the access to the motor on a 1990 yet, but when you get to it, you can remove it and observe it's operation not connected to the door. And you can try to move the door by turning the pivot rod.


I have a complete set of the duct work from a 1991. I did not see it in the car so I don't know exactly how much you have to take apart to get to the motor.


If you need trouble shooting help when you get to the motor, call me. I will be glad to help.


Jim
443-244-1347

Thanks Jim.
As always you're a life saver. Seems like this could be a big job and I hate to pull the car apart until the weather turns cold. I am going to pull the hush panel and glovebox over the weekend and see what I find. I've never been under that side of the dash. Thanks again, I'll let you know what I find.

Best, John

[-=Jeff=-]

John,

Keep in mind the carpet part on the Pass side is part of the WHOLE Dash pad, there is the lower hush but it allows a limited view

[jrd1990zr1]

John,


The Blend Door is controlled by a small electric motor and uses an electronic circuit to send position feed back to the AC Programmer. When the car is first turned ON, the AC Programmer sends a sequential full heat and full cool command to the Blend Door Motor. Since you are not seeing the movement, either the motor has failed, the AC Programmer has failed, there is a wiring problem, or the door is stuck.


I haven't investigated the access to the motor on a 1990 yet, but when you get to it, you can remove it and observe it's operation not connected to the door. And you can try to move the door by turning the pivot rod.


I have a complete set of the duct work from a 1991. I did not see it in the car so I don't know exactly how much you have to take apart to get to the motor.


If you need trouble shooting help when you get to the motor, call me. I will be glad to help.


Jim
443-244-1347

Hi Jim,

I don't want to waste your time with a long phone call until I get deeper into this. I pulled the glove compartment, other than the top of the duct work not much to see Photo 1.

Pulled the lower hush panel (Photo 2 and 3) and low and behold looks like someone was there before. Radio receiver and associated wiring is all hanging loose (Photo 4). I see the duct work and the SIR wire but nothing that looks like an actuator or motor. Am I looking in the wrong places or not far enough into this?
Thoughts?

Thanks, John

[QB93Z]

John,


In your picture 1, the duct pieces you are looking at supply the air to the small vents that blow on the passengers knees. You have to remove those ducts to get to the top of the main air box that houses the Blend Door.


Keep digging and send another picture so I can get oriented with the 1990 setup.


Jim

[Dynomite]

So Doug have you ever pulled the glove box to get the the heater box??
John

Just in case you want to pull your heater core without pulling the Dash.....
Replacing the Heater Core and Heater Hose Connection (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-7.html#post1585219751)

[Mystic ZR-1]

So Doug have you ever pulled the glove box to get the the heater box?? Before I start ripping and tearing thought I would ask. How was Carlisle, wish I had gone.

John

Hi John
Fortunately, no! Never had to go in there.
Good luck with yours.
Missed ya @ Carlisle, nice time was had by all!
D

[QB93Z]

I just remembered something about the HVAC system that affected my trouble shooting. The HVAC programmer needs to be powered off (Battery disconnected) after any changes you make to the system.


You may want to try disconnecting the battery now and see if the system returns to normal operation.


Jim

[jrd1990zr1]

I just remembered something about the HVAC system that affected my trouble shooting. The HVAC programmer needs to be powered off (Battery disconnected) after any changes you make to the system.


You may want to try disconnecting the battery now and see if the system returns to normal operation.


Jim

Thanks Jim, I'll give that a try.

Had to but it back together so I could get the mandatory annual NYS inspection. While driving there it set a Code 09 on the AC, low freon, so looks like I have a slow leak. Last charged it 2 years ago. No heat and no A/C.

Looks like I've got a couple winter projects.

John :cheers:

[jrd1990zr1]

Just in case you want to pull your heater core without pulling the Dash.....
Replacing the Heater Core and Heater Hose Connection (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-7.html#post1585219751)

Since it looks like you have had your 1990 apart some questions on the heater core removal.

If you remove the heater box from the inside can you access the blend door actuator to replace it?

Did you have to remove the fuse panel to access the heater core box?

Thanks for the information. John

[jrd1990zr1]

So I am back to trying to find the actuator for the blend door. I've removed the dash pad, lower hush panel, console trim panels, etc. Bought a fiber optic scope and still can not find the actuator.

Per the service manual, it looks like I need to remove the distribution duct which involves removing the fuse panel and instrument panel. Before I go forward I have to ask, does anyone have a better way to get to the blend door actuator rather than removing the entire instrument panel?

Below are photos of where I am now. I am really stuck, so please let me know how you have changed out the blend door actuator on a 1990.

Last question is the lower blend door pivot where the read arrow is pointing in the third picture?

Thanks

[Dynomite]

Since it looks like you have had your 1990 apart some questions on the heater core removal.

If you remove the heater box from the inside can you access the blend door actuator to replace it?

Did you have to remove the fuse panel to access the heater core box?

Thanks for the information. John

I am not sure about the blend door but the CDM had to be removed....not the fuse panel.

[QB93Z]

https://uploads.tapatalk-cdn.com/20171105/3aea91258d58ffe72dc366087145e79f.jpg

Top of blend door duct from a 1991



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[QB93Z]

I just posted a picture of the top of the duct where the blend door is located. The duct I have came from a 1991 ZR-1.


In the photo there is a small rectangular opening that reveals the upper edge of the blend door. The blend door motor is not installed in this picture. The pivot is towards the front of the duct relative to the small opening.


The photo is oriented as if you were in the passenger seat looking down on the blend door duct.

[QB93Z]

https://uploads.tapatalk-cdn.com/20171105/f45ec4c460800e34ed8026008ccbb9d3.jpg

Bottom of blend door duct. The blend door is facing the concrete in this pic.



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[jrd1990zr1]

https://uploads.tapatalk-cdn.com/20171105/3aea91258d58ffe72dc366087145e79f.jpg

Top of blend door duct from a 1991



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Jim,

I can see the white thing that looks like an intake with my fiber optic scope. Next to it is something with the # 145772 as best as I can read it. Photo of the tag is blurry, sorry. Can you tell if your 1991 box splits in half to access the actuator or can this box be removed from the inside of the car in one piece?
I am trying to avoid pulling the entire IP which is the process the Service manual directs you to to remove the air duct which is one piece across the entire width of the car. I am wondering if I pull the blend box which seems like it splits at the firewall could I then get to the actuator? I've got to believe someone must have done this on a 1990 before me. Thanks again, John :cheers:

[QB93Z]

John, I will take some better pictures tomorrow morning. Jim

[jrd1990zr1]

After two weeks of working on it, I finally got the heater core box(and actuator) removed from the car. Had to remove nearly the entire right side dashboard, high level fill, Part of the AC evaporator, fuel lines, wiper reservoir. Here is the offending part. Now I have to find a 94-95 heater core box to replace the 1990 box.

[jrd1990zr1]

So I got the bright idea (or may be not so bright) to swap out the 1990 Heater Core box with a 1994 heater core box. This would move the actuator from the top to the bottom of the heater core box. I was told on the Corvette Forum that a guy on there did this and it only required the use of a 1994 heater box, actuator and the short harness. I have a 1994 GM 16124952 actuator and the small harness from a 1992. In comparing the electrical schematics for the 1990, 1992 and 1994 model year there is no difference in the 3 harnesses other than wire color.

So before I start to reassemble the car is my conversion plan possible? Are there differences in the AC controller of a 1990 verses a 1994 which would cause this not to work? Or should I just get a new 1990 actuator and reinstall the 1990 heater box. I am at a loss on how to proceed.

Anyone who who has done this on a 1990 knows how long it takes and the PITA this job is. Your thoughts please.

Thanks,

[WVZR-1]

So I got the bright idea (or may be not so bright) to swap out the 1990 Heater Core box with a 1994 heater core box. This would move the actuator from the top to the bottom of the heater core box. I was told on the Corvette Forum that a guy on there did this and it only required the use of a 1994 heater box, actuator and the short harness. I have a 1994 GM 16124952 actuator and the small harness from a 1992. In comparing the electrical schematics for the 1990, 1992 and 1994 model year there is no difference in the 3 harnesses other than wire color.

So before I start to reassemble the car is my conversion plan possible? Are there differences in the AC controller of a 1990 verses a 1994 which would cause this not to work? Or should I just get a new 1990 actuator and reinstall the 1990 heater box. I am at a loss on how to proceed.

Anyone who who has done this on a 1990 knows how long it takes and the PITA this job is. Your thoughts please.

Thanks,

I believe you take the actuator from the '94 and use it with the original '90 assembly. I believe that you need a control, programmer and a harness to invert the assembly as you mention.

This is I believe a part # progression on the actuator 16141439 changed in 4/90 to 16145772 then to 16124952 4/92. There was some vendor changes I believe through the years and much bad stock with various numbers and lots of confusion.

If you've product with either of those numbers you'd be good I believe for any year, top or bottom so long as the control, programmer and harness match.

There's a later GM# 89018368 that is in the supersession chain but when used on other applications has met with random success. If you were to buy and want to try I'd confirm returnability if it didn't work.

[-=Jeff=-]

Here is QB93Z's thread of his replacement of the blend door motor

http://www.zr1.net/forum/showthread.php?t=27542

[jrd1990zr1]

I believe you take the actuator from the '94 and use it with the original '90 assembly. I believe that you need a control, programmer and a harness to invert the assembly as you mention.

This is I believe a part # progression on the actuator 16141439 changed in 4/90 to 16145772 then to 16124952 4/92. There was some vendor changes I believe through the years and much bad stock with various numbers and lots of confusion.

If you've product with either of those numbers you'd be good I believe for any year, top or bottom so long as the control, programmer and harness match.

There's a later GM# 89018368 that is in the supersession chain but when used on other applications has met with random success. If you were to buy and want to try I'd confirm returnability if it didn't work.

WVZR-1 and -=Jeff=-, Thank you for the information. Your posts made me pause and think about changing the box to a 1994 heater box. I also e-mailed Bryan Thompson at Batee about the conversion and he told me that the AC programmer and the ECU on a 1990 ZR1 are paired and I could not switch out the AC programmer, control head and heater box to a 1994 version. So it appears the best course of action is to keep the 1990 intact as a 1990.

I have a used GM 16124952 actuator so I am going to try it on the 1990 heater box before I put it back in the car. If this does not work, I spoke with AC Delco and they crossed GM 16124952 to AC Delco 15-71937 which I can still get from their central warehouse. I will get a new actuator and try that. If it still doesn't work I am going to pull the AC Programmer, control head and actuators and send them to BATEE for bench testing. Bryan has graciously offered to check out the components to locate the problem.

Thank you for your thoughts above. :cheers:

[-=Jeff=-]

Interesting Comments by Bryan,

My friend's 1990 had an issue and I think a programmer from a 95 or 96 worked..

Also I think the control heads were all the same, sans the color changes

[WVZR-1]

The 15-71937 is the ACD for the 89018368 that I mentioned. If you decide to buy and try confirm it's returnable if it doesn't work. A friend at a dealer has mentioned problems for some of these newer actuators.

I'd suggest a conversation with a local ACD jobber or a dealer before the buy.

[jrd1990zr1]

The 15-71937 is the ACD for the 89018368 that I mentioned. If you decide to buy and try confirm it's returnable if it doesn't work. A friend at a dealer has mentioned problems for some of these newer actuators.

I'd suggest a conversation with a local ACD jobber or a dealer before the buy.

Actually I stopped by the local ACD jobber (United Auto), gave them the GM 16124952 and it crossed to ACD 15-71937. They called TN while I was there and they verified availability. Generally I think all electrical components are not returnable, so that may not be an option. Do you know of a better way to proceed? Do you know what the dealer does when they run into this problem?

Thanks. :cheers:

[jrd1990zr1]

Interesting Comments by Bryan,

My friend's 1990 had an issue and I think a programmer from a 95 or 96 worked..

Also I think the control heads were all the same, sans the color changes

Jeff this is the quote from Bryan. Maybe I misunderstood.

"I don't think changing the year programmer is in your interest. The LT-5s use a different signaling method to communicate with the ECU, and they changed over time, so whatever you do, stick with the correct part for your year car."

So the way I understand it the actuator regardless of position on the top or bottom of the heater core box is controlled by the AC programmer. I'd have to switch to a 1994 programmer which might not communicate with my 1990 ECU. Unless I am misunderstanding . So my best route appears to be the stay with the 1990 components, once I find an actuator I am sure works.

Is my logic sound?

Thanks. :cheers:

[-=Jeff=-]

How much is the part? if not too much might be worth getting

[-=Jeff=-]

Jeff this is the quote from Bryan. Maybe I misunderstood.

"I don't think changing the year programmer is in your interest. The LT-5s use a different signaling method to communicate with the ECU, and they changed over time, so whatever you do, stick with the correct part for your year car."

So the way I understand it the actuator regardless of position on the top or bottom of the heater core box is controlled by the AC programmer. I'd have to switch to a 1994 programmer which might not communicate with my 1990 ECU. Unless I am misunderstanding . So my best route appears to be the stay with the 1990 components, once I find an actuator I am sure works.

Is my logic sound?

Thanks. :cheers:

I don't think you have an issue with swapping the Programmer. The ECU communication is different yes, but I don't think that will effect the Programmer. I don't think I have any extras any more, but I know the controller is compatible for all years.. I think you would be fine

[WVZR-1]

Actually I stopped by the local ACD jobber (United Auto), gave them the GM 16124952 and it crossed to ACD 15-71937. They called TN while I was there and they verified availability. Generally I think all electrical components are not returnable, so that may not be an option. Do you know of a better way to proceed? Do you know what the dealer does when they run into this problem?

Thanks. :cheers:

Try the actuator you have and if you decide to buy talk to United and explain you've been told there are maybe issues with the part# supercession and ask if it's returnable to them if it doesn't function.

Talk to a local dealer also maybe - buy from whichever understands the issues. Works you keep, doesn't you return - maybe offer to accept merchandise credit if you need to return!

Try to negotiate a price to maybe something $80 or less!

[WVZR-1]

swapping the programmer?

GM SPO has different part # for MY and also engine RPO -

92-93 - LT1

92-93 - LT5

94-95 - LT1

94-95 - LT5

Seems that when they started to supply REMAN they would have consolidated the part #'s. My SPO information was current in year 2000

Consider also that with R134 conversion in '94 there was likely different values expected from components. I've certainly no 1st hand experience but I ain't wanting to try

[jrd1990zr1]

Try the actuator you have and if you decide to buy talk to United and explain you've been told there are maybe issues with the part# supercession and ask if it's returnable to them if it doesn't function.

Talk to a local dealer also maybe - buy from whichever understands the issues. Works you keep, doesn't you return - maybe offer to accept merchandise credit if you need to return!

Try to negotiate a price to maybe something $80 or less!

I will try the two I have tomorrow.

Also spoke with my local chevy dealer. GM16124952 is NLA, checked nationwide database NLA. I gave them ACD 15-71937 which they said crosses to GM89018368 (as you said) which is readily available. $138.00 non-returnable.

ACD 15-71937 is available from United for $95.00 and is non returnable.

I will probabily end up buying the ACD one if the two I have do not work.

I don't mind spending the $100 if I can get this working, this is the worst repair I have had to make on a corvette, I am just getting frustrated.

I think swapping the 1990 programmer with a 1994 at this point is a not going to happen.

Sorry for the drama.

[-=Jeff=-]

Yeah I understand. I need to read through the thread again to see what you have already done


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[WVZR-1]

Also spoke with my local chevy dealer. GM16124952 is NLA, checked nationwide database NLA. I gave them ACD 15-71937 which they said crosses to GM89018368 (as you said) which is readily available. $138.00 non-returnable.

ACD 15-71937 is available from United for $95.00 and is non returnable.

I will probabily end up buying the ACD one if the two I have do not work.
don't mind spending the $100 if I can get this working, this is the worst repair I have had to make


If you can confirm the actuator is needed then the purchase from either will afford you the warranty. If a new purchase doesn't work they would be obligated to supply the second or I suppose with a discussion that you suspected maybe not a valid replacement refund the purchase.

Ultimately I believe the best buy is the "local" and NOT an Internet buy.

[jrd1990zr1]

Put the wiring back together, attached an actuator to the box went from full cold to hull heat and it set code 01. At full code the blend door closes over the heater core as it should. At full heat the door opens about 1/2 inch and slowly flutters. Tried two more actuators did the same with all. Went through the FSM procedure it appears the programer is the problem. Called Bryan Thompson he also believes this is a programer problem. So the plan is now to remove the programmer, control head and put them in a box with my actuators to Bryan.

I wish the blend door had been fluttering before I removed the heater box, might have saved some work.

[WVZR-1]

Put the wiring back together, attached an actuator to the box went from full cold to hull heat and it set code 01. At full code the blend door closes over the heater core as it should. At full heat the door opens about 1/2 inch and slowly flutters. Tried two more actuators did the same with all. Went through the FSM procedure it appears the programer is the problem. Called Bryan Thompson he also believes this is a programer problem. So the plan is now to remove the programmer, control head and put them in a box with my actuators to Bryan.

I wish the blend door had been fluttering before I removed the heater box, might have saved some work.

I'd be interested in the part# on the label of the programmer when you remove it. I believe I've one stuffed away somewhere but it's difficult to put a 'hands-on' currently.

[jrd1990zr1]

I'd be interested in the part# on the label of the programmer when you remove it. I believe I've one stuffed away somewhere but it's difficult to put a 'hands-on' currently.

No part number that I can find. See attached photos. One corner is broken on the case and the retainer was not on the silicone plug. Just held on with a flat washer.

During removal I somehow pulled the tan line from the silicone plug. I did not see a diagram of which color goes where in the plug. There are more ports than vacuum lines. Do you know where I can find a diagram? Also any thoughts on an adhesive to seal the tubes to the block? They do not seem secure.