Electronic A.C. issues - ZR-1 Net Registry Forums

tiegsd · 11-18-2017

Neither A.C. nor heat seems to work on my 90 ZR-1, wondering if it might be common failure mode? Electronic unit seems functional, but just blows cold air when it's cold out, hot air when it's hot out. Has anyone seen this on their s, or do you think they are separate issues?

Sent from my SM-N920V using ZR-1 Net Registry mobile app

Marc Haibeck · 11-19-2017

The AC system is more complicated than the heating system. Fix the heating problem first.

Coolant always flows to the heater core when the engine running. There is no water valve for the heater core. Check the two large tubes running over the right wheel area. They should both be hot, close to the engine temperature. If not the heater core is clogged with debris. Try backflushing it. The 3/4" tube is the outlet.

If both tubes are hot. Maybe the air temperature door has a problem. Remove the blower speed control module located on top of the HVAC air box. It has two electrical connectors on it. Observe the temperature door. Have a helper vary the interior temperature setting from 60 to 85 degrees. The door should move in proportion to the temperature request. If not there may be a problem with the servo motor.

tiegsd · 11-19-2017

Will do. Many thanks Marc!

Sent from my SM-N920V using ZR-1 Net Registry mobile app

jrd1990zr1 · 11-27-2017

I hope you have more luck with your system than I did. Blend door motor (actuator) was bad. Have to remove most of the right side dashboard and the evaporator case to remove the heater core box then I was able to remove the actuator. I also have a 1990 no heat post. Here is a picture of the 1990 actuator on the heater core box.

tiegsd · 12-01-2017

Quote:

Originally Posted by jrd1990zr1

I hope you have more luck with your system than I did. Blend door motor (actuator) was bad. Have to remove most of the right side dashboard and the evaporator case to remove the heater core box then I was able to remove the actuator. I also have a 1990 no heat post. Here is a picture of the 1990 actuator on the heater core box.

Many thanks, appreciate the pic! Hoping to get to this over the holidays.

JFFerner · 12-01-2017

Although there's probably no correlation to your heat problem, you may want to try that which I do to my '90 once every year to 18 months to get the A/C working. Simply disconnect a battery cable for a moment or two and then reconnect it. I know something must be screwed up, but at least for me, the temporary cure is the quickest and cheapest. Good luck.

tiegsd · 12-02-2017

Quote:

Originally Posted by JFFerner

Although there's probably no correlation to your heat problem, you may want to try that which I do to my '90 once every year to 18 months to get the A/C working. Simply disconnect a battery cable for a moment or two and then reconnect it. I know something must be screwed up, but at least for me, the temporary cure is the quickest and cheapest. Good luck.

Interesting, wonder why that makes the A/C work again?

Had to disconnect Battery recently for something else, so I imagine that by doing that I cleared any fault codes that were logged by the Elec AC computer. Who knows, maybe I'll get lucky! It'll give me something to do this weekend besides watching football.

-=Jeff=- · 12-02-2017

Also with electronic AC when you pull the battery. on first key, I always turn to on and waiting until after the blend door motor is done calibrating before starting the car

tiegsd · 12-03-2017

Well, not sure what happened, but felt heat coming out of the vents for the first time yesterday on a short trip down to Effingham, IL. Pretty happy about that.

Since I was motivated by undeserved success, I took a look at my rear hatch support struts since I need to replace them and found that the passenger side electrical connector for the rear hatch defroster is gone, busted off by a previous owner.

Ccmano · 12-03-2017

Quote:

Originally Posted by tiegsd

Since I was motivated by undeserved success, I took a look at my rear hatch support struts since I need to replace them and found that the passenger side electrical connector for the rear hatch defroster is gone, busted off by a previous owner.

Mine too, and it’s in an awkward place to try and resolder. Short of removing the glass hatch, flipping it over, laying it down and resoldering that way, I have yet to come up with a simpler on the car fix.
H

11-18-2017	#1
tiegsd Join Date: Jul 2017 Location: West Chester, PA Posts: 376	Electronic A.C. issues Neither A.C. nor heat seems to work on my 90 ZR-1, wondering if it might be common failure mode? Electronic unit seems functional, but just blows cold air when it's cold out, hot air when it's hot out. Has anyone seen this on their s, or do you think they are separate issues? Sent from my SM-N920V using ZR-1 Net Registry mobile app __________________ 1990 Black/Black ZR-1 #1155 1993 White/Red coupe (Regrettably sold)

11-19-2017	#2
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 241	Re: Electronic A.C. issues The AC system is more complicated than the heating system. Fix the heating problem first. Coolant always flows to the heater core when the engine running. There is no water valve for the heater core. Check the two large tubes running over the right wheel area. They should both be hot, close to the engine temperature. If not the heater core is clogged with debris. Try backflushing it. The 3/4" tube is the outlet. If both tubes are hot. Maybe the air temperature door has a problem. Remove the blower speed control module located on top of the HVAC air box. It has two electrical connectors on it. Observe the temperature door. Have a helper vary the interior temperature setting from 60 to 85 degrees. The door should move in proportion to the temperature request. If not there may be a problem with the servo motor.

11-19-2017	#3
tiegsd Join Date: Jul 2017 Location: West Chester, PA Posts: 376	Re: Electronic A.C. issues Will do. Many thanks Marc! Sent from my SM-N920V using ZR-1 Net Registry mobile app __________________ 1990 Black/Black ZR-1 #1155 1993 White/Red coupe (Regrettably sold)

12-01-2017	#6
JFFerner Join Date: Jan 2012 Location: Dallastown, PA Posts: 189	Re: Electronic A.C. issues Although there's probably no correlation to your heat problem, you may want to try that which I do to my '90 once every year to 18 months to get the A/C working. Simply disconnect a battery cable for a moment or two and then reconnect it. I know something must be screwed up, but at least for me, the temporary cure is the quickest and cheapest. Good luck.

12-02-2017	#8
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,146	Re: Electronic A.C. issues Also with electronic AC when you pull the battery. on first key, I always turn to on and waiting until after the blend door motor is done calibrating before starting the car __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

12-03-2017	#9
tiegsd Join Date: Jul 2017 Location: West Chester, PA Posts: 376	Re: Electronic A.C. issues Well, not sure what happened, but felt heat coming out of the vents for the first time yesterday on a short trip down to Effingham, IL. Pretty happy about that. Since I was motivated by undeserved success, I took a look at my rear hatch support struts since I need to replace them and found that the passenger side electrical connector for the rear hatch defroster is gone, busted off by a previous owner.