Power key switch question

[Ozruss90]

Can someone please confirm that the power switch, switches negative?
Pulled my switch out and apart, thinking there maybe a problem, as my full power does not light up in the dash panel and my secondaries do NOT work.
Switch works fine so l put a test lamp on the connector plug on the back of the switch with the ignition on. No power at either side of the plug ( so lm thinking it switches negative?)
If this is all correct and working, why no light on the dash panel?
Help please

Cheers from down under 🇦🇺
Russell

[QB93Z]

What year is your ZR-1? The Power Switch for 1990 is different from 1991-1995.

Jim

[tccrab]

Perhaps the bulb in the DIS is burnt out?

Is there a noticeable difference between the lower power setting and the high power setting?
It will be obvious if your secondaries are working or not.

'Crabs

[Ozruss90]

What year is your ZR-1? The Power Switch for 1990 is different from 1991-1995.

Jim

The car is 1990, #1948. 11k Miles

[Ozruss90]

Perhaps the bulb in the DIS is burnt out?

Is there a noticeable difference between the lower power setting and the high power setting?
It will be obvious if your secondaries are working or not.

'Crabs

Problem is l don’t have another ZR-1 to compare it to. Few and far between over here in OZ. But after being on this forum for the last couple of years and reading all the different posts about how mighty the LT5 is, mine must have a problem somewhere. Average of the mark and won’t pull past 5k revs. Nice to drive but not living up to the ZR-1 reputation .

[Reichert]

recommended reading: http://www.zr1specialist.com/HAT%20Web/articles/Are%20The%20Secondaries%20Working.pdf

[lfalzarano]

If the vacuum line accidentally came apart, it would give you the poor power feeling.

The valet parking switch (LT5), located on the accessory trim plate, sends a signal to the ECM. With the key in the “NORMAL" position one set of injectors operate while the “FULL" position activates a second set of injectors, a second fuel pump and a second throttle plate which increases engine power. Key may be removed only in the “NORMAL" position.

I’d check your fuses and a possible broken wire or loose connection. There should be power to the key, which will light up the Full on the display and the secondary injectors. When you get that light working, the ZR-1 will light you up on FULL throttle!


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[geezer]

Ozruss90 : This may help.

[Ozruss90]

Thanks Lou and Geezer.
If it is just a fuse, then I’ll be rapt. Been thinking my problem was under the plenum all this time. Not sure where to locate the suspect fuse . All the fuses in the main fuse block on passenger end of the dash seem ok. Is the fuse for the valet/power switch somewhere else? Not sure where to look.

Cheers
Russell

[geezer]

Russell: Valet switch shares the CCM fuse (10 amp) Main Fuse Block-- along with O2 sensors, rear defog, AC clutch relay,heater & A/C programmer

[WVZR-1]

OP - diagram in post 8 is incorrect and I'd think there's likely other incorrect comments. Do you have a '90 FSM? I sent you a PM with my email. If you don't have a '90 FSM email me and I'll see that you get a 'correct' one. Mine is a 'pdf that's very searchable and has no 'watermarks'. Many have mine. You can have mine in a matter of minutes for all of your diagnostics!! I'll include for you a '90 parts publication also!!

I've FSM in New Zealand and most other countries.

[Ozruss90]

Russell: Valet switch shares the CCM fuse (10 amp) Main Fuse Block-- along with O2 sensors, rear defog, AC clutch relay,heater & A/C programmer

Thanks Geezer,
That fuse checked out ok, plus my A/C and heater work fine, which tells me the fuse is fine. Don’t have power though at the connector plug that goes on the back of the valet/power switch( ignition key ON ).
Cheers. Russell

[lfalzarano]

It's in the main block - 5Amp fuse

[WVZR-1]

It's in the main block - 5Amp fuse

I've sent the OP a correct '90 FSM so he'll be better prepared for diagnostic help regarding the '90. I believe you've mine also. Is it doing well for you? The other 1/2 of that image shows the pump fusing also. I've mentioned the page # and the 8A22-10 to the OP to check out when he gets the FSM on his PC etc.

It will be much easier for people to help him after he has the FSM !!

OP is GMT +11 so I imagine he's very sound asleep - we'll see what his AM brings him.

[lfalzarano]

I just Window snipped it from the manual. Great investment and easier to locate the information without going out to the frozen garage to retrieve the paper manual.

I’ve used it a few times. Mechanics today refuse to real it when I send it for repairs, like changing tires. I print out the procedures for the LTPS bands so they don’t break them. They still screw up. Next time, I’ll have them removed on the next tire change!


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[WVZR-1]

I just Window snipped it from the manual. Great investment and easier to locate the information without going out to the frozen garage to retrieve the paper manual.

I’ve used it a few times. Mechanics today refuse to real it when I send it for repairs, like changing tires. I print out the procedures for the LTPS bands so they don’t break them. They still screw up. Next time, I’ll have them removed on the next tire change!




Do you use the 'SNAPSHOT' function in Adobe and the EDIT > drop-down. With my .pdf the EDIT > SNAPSHOT works and then I just toss it to PAINT and then a .JPG. A 'SECURED' .pdf doesn't allow the 'SNAPSHOT function.

You maybe let your 'browser' do your .pdf?

Most everyone with mine and also a paper tell me that it's a tremendous 'INDEX'. I've become so accustomed to the .pdf I seldom open a paper manual.

[lfalzarano]

I always use the Windows Snipping tool and save it as a Gif or whatever, then upload it. If you notice, the snip was only a portion of the page. It's just easier to me and meets the posting limits.

Although I used the snapshot for the pages for the idiot mechanics. Works great

[geezer]

Thanks for the correction of the info. I posted! In error took it form my '91 Service Manual so clearly change b'twn '90 & '91.
My apology to Ozruss90 for this!

[lfalzarano]

Russell: Valet switch shares the CCM fuse (10 amp) Main Fuse Block-- along with O2 sensors, rear defog, AC clutch relay,heater & A/C programmer



5 Amp in the Cluster in the main box


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[lfalzarano]

Thanks for the correction of the info. I posted! In error took it form my '91 Service Manual so clearly change b'twn '90 & '91.

My apology to Ozruss90 for this!



Only the 90’s. 91-95 are different, but your second page is correctly depicting the valet key diagram, although I’m shopping for new glasses tomorrow. iPhone is killing my eyes, but it’s so convenient[emoji16]


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[Ozruss90]

Just got home from a work trip last night. Had visitors for dinner, so no work on the Z. When l get home from work tonight, I’ll be heading for the shed, armed with new info that was forwarded on to me. Many thanks WVZR-1 for your help.
Hopefully can work it out. Stay tuned for an update .

Cheers from down under 🇦🇺

Russell

[Ozruss90]

Ok, so latest update.
.. Valet switch tested and works fine.
.. Power at main fuse panel as per normal and 5 amp fuse ok
.. Still no Full Engine Power light on in the DIC
I’m assuming that if the globe in the DIC is out, it would cut the circuit and prevent the operation of the secondaries ( looking at the diagram at 8a-82-4)

Went take off the DIC front panel, 3 torx screws accessible but the top RH screw is behind a section of dash padding and not accessible.
Can someone please help with the removal of the DIC to check globe.
Hope I’m the right path here.

Cheers
Russell

[lfalzarano]

Before tearing up the DIC display, I would take the car out, warm it up, then redline it. If you notice extreme acceleration, then the bulb is out. [emoji23]


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[lfalzarano]

Use this to Chart #29 page 8A-82-21 to diagnose the DIC "Full Power" light. Good Luck :cheers:


BTW: with the engine off, turn the key just before the Start detent. That is the "Bulb Test" for the DIC. All indicators should light up, including the "Full Power" bulb.:-D

"Full Engine Power" Indicator
(VIN J Only)
When the Valet Mode Switch is moved to "ENGINE POWER," the switch will apply ground to one side of the "Full Engine Power" Indicator bulb, illuminating it.

[Ozruss90]

Use this to Chart #29 page 8A-82-21 to diagnose the DIC "Full Power" light. Good Luck :cheers:


BTW: with the engine off, turn the key just before the Start detent. That is the "Bulb Test" for the DIC. All indicators should light up, including the "Full Power" bulb.:-D

"Full Engine Power" Indicator
(VIN J Only)
When the Valet Mode Switch is moved to "ENGINE POWER," the switch will apply ground to one side of the "Full Engine Power" Indicator bulb, illuminating it.

Thanks Lou,
When the ignition key turned to ON, prior to start “bulb test” the FULL POWER does NOT come on in the DIC and never has.
There IS power at the appropriate fuse within the main fuse block.
The ground side of the valet switch DOES in fact go earth. Tested.
So.......Power at the fuse✔️ No power at the Valet switch ✖️
Globe that lights the Full Power lamp in the DIC that does NOT work is between the fuse and the valet switch
It appears it needs the globe to be working correctly, to complete the whole circuit.
I’m still leaning towards the globe being out .
Have l miss diagnosed this.?????

Cheers
Russell

[lfalzarano]

According to the chart I sent last, it can be a broken wire in the circuit, bulb or the flexible circuit board. The last would be tough to source and replace. [emoji1317] Hoping it is one of the 1st two. Good Luck.


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[Ozruss90]

LATEST UPDATE.
Pulled the DIC out of the car . As suspected a blown globe for the Full Engine Power circuit. Special type of twist in globe and globe holder that l couldn’t get, so l robbed a globe/globe holder unit from the service engine soon circuit and put it in place of Full Engine Power.
Replaced DIC back into dash, re-connected battery, connected valet switch (temporarily), turned key to on and now had Full Engine Power light up in the DIC.
Put everything back together and took the the car for a test run.
Well We’ll Well. I now have a ZR-1 that goes like a ZR-1 should.
Spins up to 7k rpm easily and pulls hard.
Certainly put a smile on my face.😀😀

Just need to track down where to get these little globe/globe holder units from so l can replace the one l robbed .

Cheers from down under 🇦🇺
Russell

[lfalzarano]

I would assume you might get a globe/globe holder from a Service Soon part from a wreaked regular C4 of that vintage at a junk yard. Not sure that electrical part is available online. Someone on the forum might assist with a source.


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[WVZR-1]

That's good to hear. I'd think a PC74 bulb/socket wouldn't be a difficult find even in AU. PC74 I believe should have a grey socket. Any year '90+ C4 in the DIC would use PC74 same bulbs

[aafc]

For the globe/ lamp check out this web site batee.com. He has a good line of parts and repair information for ZR-1's and reg C4's instruments.
John
1990 white/black #2546
one of a few auto Eq 4l8OE's ZR-1's

[Ccmano]

LATEST UPDATE.
Pulled the DIC out of the car . As suspected a blown globe for the Full Engine Power circuit. Special type of twist in globe and globe holder that l couldn’t get, so l robbed a globe/globe holder unit from the service engine soon circuit and put it in place of Full Engine Power.
Replaced DIC back into dash, re-connected battery, connected valet switch (temporarily), turned key to on and now had Full Engine Power light up in the DIC.
Put everything back together and took the the car for a test run.
Well We’ll Well. I now have a ZR-1 that goes like a ZR-1 should.
Spins up to 7k rpm easily and pulls hard.
Certainly put a smile on my face.😀😀

Just need to track down where to get these little globe/globe holder units from so l can replace the one l robbed .

Cheers from down under 🇦🇺
Russell

That’s fantastic! Funny how it’s sometimes the simple things that confound us the most. Great to see you stuck to it and systematically got to the root of the problem. Good work.
H
:cheers:

[secondchance]

Check with BATEE.com.
http://batee.com/corvette/dcrg/services/9096_services.html

[WVZR-1]

I don't know who imports into AU directly. The last time I bought 'NEW' PC74 bulbs I bought MOPAR L000PC74 and they were less than $3 each. They were used on many MOPAR/JEEP through 2007 or so. A person just needs to just confirm 'grey' socket and fit. L'zero, zero,zero PC74

I believe the OP likely just swapped because of the weekend and to confirm his diagnostics. All of us would likely have done the same given the circumstances. I'd think in the after-market even in the AU or like I mentioned from another '90+ DIC the OP can be helped. Many of us have a used DIC with 7 or 8 of what the OP needs. He's just a long ways off!

A GM 25086809 bulb is a PC74 but has a terrible price these days. Still available but expensive!

[Ozruss90]

Thanks to everyone for your assistance and input. Greatly appreciated.
And yes Dave, they are a grey bodied PC74 as mentioned and yes I did the swap just to test. Unreal to think that just that little globe being out was stopping my secondaries from operating. I haven’t even started to look for the globe over here in Oz. Will do that this week, and if don’t do any good, looks like Batee as previously mentioned has them.

Cheers.
Russell

[Joelbbvette]

As for the #74 bulb, it can be pulled out of the plastic holder and a new one inserted. I did this during my PV and it worked. Good luck and glad to hear you have a Full Power ZR-1 again.

[Ozruss90]

As for the #74 bulb, it can be pulled out of the plastic holder and a new one inserted. I did this during my PV and it worked. Good luck and glad to hear you have a Full Power ZR-1 again.

Tried pulling the bulb out of the grey plastic holder, but it smashed doing so. Assumed it wasn’t possible. Can buy them locally here in town at the local Chrysler/Jeep dealer, part number L000PC74. Complete unit at $2.95 each.
The only downside to this outcome is the fuel gauge will probably drop a bit bit quicker than before. HANG ON, no downside, l don’t care.

Cheers, Russell

[WVZR-1]

Tried pulling the bulb out of the grey plastic holder, but it smashed doing so. Assumed it wasn’t possible. Can buy them locally here in town at the local Chrysler/Jeep dealer, part number L000PC74. Complete unit at $2.95 each.
The only downside to this outcome is the fuel gauge will probably drop a bit bit quicker than before. HANG ON, no downside, l don’t care.

Cheers, Russell

That's the way I've always done PC base bulbs. Apparently Joel is using the T-1 3/4 vs the purchase of the GM assembled part. The L000PC74 is currently a black base but I'd think fine. The T-1 3/4 bulb I'd think a more difficult find. Is the L000PC74 in stock @ your local dealer?

Bulb is busted now but who knows - maybe the socket!!

Looks like the dealer is maybe only a 10 minute drive?

[secondchance]

Best way to remove these tiny wedges is to attach small pieces of 3M double stick tape on both legs of a tweezers. This allows tweezers to grab the bulb with out excessive pressure.

[precast1]

As for the #74 bulb, it can be pulled out of the plastic holder and a new one inserted. I did this during my PV and it worked. Good luck and glad to hear you have a Full Power ZR-1 again.Joel when you have a moment explain to me how to get to these bulbs and where to purchase the #74 bulbs. I have not had the car out since I put the A Molds and new tires on I didn't install the sensors so the low tire pressure light may stay on. Call me I also need your address so I can send you the oil filter. The stickers came in today.

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[Ozruss90]

That's the way I've always done PC base bulbs. Apparently Joel is using the T-1 3/4 vs the purchase of the GM assembled part. The L000PC74 is currently a black base but I'd think fine. The T-1 3/4 bulb I'd think a more difficult find. Is the L000PC74 in stock @ your local dealer?

Bulb is busted now but who knows - maybe the socket!!

Looks like the dealer is maybe only a 10 minute drive?

Chrysler / Jeep dealer only 5 minutes from home. Didn’t have them in stock, but the part number came up as correct for the part. 24 hr to order in.

[WVZR-1]

Chrysler / Jeep dealer only 5 minutes from home. Didn’t have them in stock, but the part number came up as correct for the part. 24 hr to order in.

I took a DIC and a couple sockets to a local CMC/Jeep dealer that had in stock and there's no issues. The last time I did a cluster rebuild (NOT C4) I believe the L000PC74 was grey. It's been easily 10+years.