1990 ZR-1 A/C issues PLEASE HELP IT'S HOT AS HELL
Thread Starter
Instructor
Joined: Nov 2011
Posts: 211
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1990 ZR-1 A/C issues PLEASE HELP IT'S HOT AS HELL
Hello everybody,
Today I am calling on all you C4 A/C Gurus out there. I have a customer who has been trying to diagnose a problem with the A/C on his 90 ZR1. I have already rebuilt his climate control head and tested good but he is till having some other issues, I will post the email he sent to me hopefully one of you can help. Here is his email :
Hi Tyler
I managed to display the Diagnostic Trouble Codes on the heater control.There are about 37 different menus to scroll through.Almost all have some kind of a code number.Where do i find information on the code faults?
Below is the a/c issue that I am working through.
Help my a/c on my 1990 ZR1 #1675 is not working. It was working one day than just quite blowing cold air.
I have replaced the a/c relay (under the driver dash, second one in from the outside of the car).Also sent out the controller to have checked and repaired. A/C still not working.
The compressor will engage when I jump the low pressure switch.
The compressor will also engage when I ground the grey wire on the a/c relay plug.
With the grey wire grounded the air will blow cold (44*F).As soon as I disconnect the ground the air temp rises. What should I check next?
Thank you for your help Roy
Thanks for you help guys Roy is not the best on the computer and I want to see the guy enjoy his ZR1 this summer lets help this guy get back on the road! TIA
Today I am calling on all you C4 A/C Gurus out there. I have a customer who has been trying to diagnose a problem with the A/C on his 90 ZR1. I have already rebuilt his climate control head and tested good but he is till having some other issues, I will post the email he sent to me hopefully one of you can help. Here is his email :
Hi Tyler
I managed to display the Diagnostic Trouble Codes on the heater control.There are about 37 different menus to scroll through.Almost all have some kind of a code number.Where do i find information on the code faults?
Below is the a/c issue that I am working through.
Help my a/c on my 1990 ZR1 #1675 is not working. It was working one day than just quite blowing cold air.
I have replaced the a/c relay (under the driver dash, second one in from the outside of the car).Also sent out the controller to have checked and repaired. A/C still not working.
The compressor will engage when I jump the low pressure switch.
The compressor will also engage when I ground the grey wire on the a/c relay plug.
With the grey wire grounded the air will blow cold (44*F).As soon as I disconnect the ground the air temp rises. What should I check next?
Thank you for your help Roy
Thanks for you help guys Roy is not the best on the computer and I want to see the guy enjoy his ZR1 this summer lets help this guy get back on the road! TIA
Race Director
Joined: Feb 2002
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From: Compound in the Grove, Ga.
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St. Jude Donor '16
Check the AC programer on the firewall inside car just above the gas pedal. head unit sends signal to it than to (PCM may be ECM on 90 my book is a 96) and on to relay. Two common issues with the programer are vents will not change or no AC. or could be a pressure switch.
Last edited by FASTAZU; Jul 5, 2013 at 08:03 PM.
Thread Starter
Instructor
Joined: Nov 2011
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Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
When you hold the up and down arrows on the control head for
a couple of seconds it goes into diagnostic mode.
-00 is displayed. The - sign indicates you are looking at a
Parameter. To see what's stored in that location you press
the Auto button.
To reset a code 09 (Low Freon) you disconnect and reconnect the battery cable.
After that when the ignition is turned on, the AC Programmer recalibrates the blend door which takes around 30 seconds.
When he's grounding the Grey wire, he's manually enabling
the AC Clutch relay. The normal signal flow is from the AC Programmer to the ECM and the ECM grounds the Gray wire.
If you have a volt meter you can monitor the AC request signal from the Programmer. When AC is selected the AC Request voltage signal level should change.
The ECM above the battery has 4 plugs going to it. The AC request signal is on the Green ECM connector Pin 2 a Grey/Red wire. You have to pierce the wire with a needle or sharp probe to measure the voltage on it.
Last edited by Hooked on Vettes; Jul 5, 2013 at 07:39 PM.
Race Director
Joined: Sep 2001
Posts: 14,648
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From: NEwhere Ohio
Race Director
Joined: Feb 2002
Posts: 11,596
Likes: 1,053
From: Compound in the Grove, Ga.
2026 Corvette of the Year Finalist - Unmodified
2025 C4 of the Year Winner - Unmodified
2024 C4 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (performance mods)
2018 C4 of Year Finalist
2015 C4 of the Year Finalist
St. Jude Donor '16
If it low on freon not only should you get an 090 code on the head unit the off button light should be flashing.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The path to the Low Pressure Switch is from the Relay so if it runs when you jumper that harness, the connection at the Pressure Switch is fubar or it's the Switch. Switch contacts are closed above 50 psi so take a DVM and verify that the Switch Contacts are a completed circuit. If not, and no low gas code, replace it. If so, the Connector needs to be diddled with or replaced.
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Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
He wouldn't be blowing 44° air with an empty/Low system... but he mentioned; "The Compressor will engage When I jumped the low pressure switch" Thats were I would be looking.
