90 HVAC diagnose procedure?
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
90 HVAC diagnose procedure?
I was told this may be where the problem lies and no 0 about any of it.
Occasionally the "auto" light would come on when I started the car, figured the "off" button was sticky, get to it when I get to it type thing. Never use it anyway.
2 days ago the off button was blinking...
Went back to normal (solid "off" light) , no issues.
This afternoon upon starting the car my stereo lost its presets, outside temp was reading 20 deg cooler than it was, heater came on while in "off".
Whats up, anyone dealt with this before ?
Occasionally the "auto" light would come on when I started the car, figured the "off" button was sticky, get to it when I get to it type thing. Never use it anyway.
2 days ago the off button was blinking...
Went back to normal (solid "off" light) , no issues.
This afternoon upon starting the car my stereo lost its presets, outside temp was reading 20 deg cooler than it was, heater came on while in "off".
Whats up, anyone dealt with this before ?
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Dont know.
Was advised to turn key to "On pos." and hold down both buttons for fan speed til 00 appeared. If there is a code it should show. If no code "00" will continue to show...Scrolled "up", nothing.
I was also told the "Off" button was blinking to do that procedure then. It did it once yesterday, seems Ok now.
However I tried it twice. First time the outside temp read correct (73), second time it read 50...same as earlier this afternoon.
Maybe it needs more time for something more obvious to show up?
Thanks Jeffvette for the tips.
Any more input?
Was advised to turn key to "On pos." and hold down both buttons for fan speed til 00 appeared. If there is a code it should show. If no code "00" will continue to show...Scrolled "up", nothing.
I was also told the "Off" button was blinking to do that procedure then. It did it once yesterday, seems Ok now.
However I tried it twice. First time the outside temp read correct (73), second time it read 50...same as earlier this afternoon.
Maybe it needs more time for something more obvious to show up?
Thanks Jeffvette for the tips.
Any more input?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Procedure is here: https://www.corvetteforum.com/techti...=193&TopicID=2
Run again and post all of the outputs. Generally, they'll show whether or not the Programmer is capable of reading data and communicating that info through the Display. You then can make a decision on whether or not it's garbage in/garbage out; ie a funky sensor or a bum Programmer. An HVAC Control Problem (dash unit) would usually be no info at all, but the fact that's indicating a problem would seem to rule that out.
Run again and post all of the outputs. Generally, they'll show whether or not the Programmer is capable of reading data and communicating that info through the Display. You then can make a decision on whether or not it's garbage in/garbage out; ie a funky sensor or a bum Programmer. An HVAC Control Problem (dash unit) would usually be no info at all, but the fact that's indicating a problem would seem to rule that out.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Ok - post what it spits out. Re-reading what you've got so far, this sounds like a memory problem or maybe even something with the Dash or CCM which would tie in the HVAC and Radio - possibly an intermittent ground.
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Wha confused me is the stereo lost its presets just that one time at the same time the AC went wacky. . Is this tied in somewhere?
THis morning it acted normally...THis afternoon coming home from work when I had the key in the "on" pos. the outside temp read 170. When I statrted it it read correctly, 89 deg. After 5 seconds it went to 50 like it did yesterday.
THis morning it acted normally...THis afternoon coming home from work when I had the key in the "on" pos. the outside temp read 170. When I statrted it it read correctly, 89 deg. After 5 seconds it went to 50 like it did yesterday.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I believe there's a serial bus between the Radio, HVAC and Dash - all via the CCM. This is a ZR1 right? Loss of presets would be loss of memory and that's often a funky ground. Prior to '90, the main dash and HVAC ground (G201) ran to the driver's side footwell with the HVAC on a separate wire, but terminating at the same lug. Unfortunately, I don't have a schematic for your Year (or any of the ZR-1's) though parts of the LT-5 harness was included in all of the '89's (and I often find wires to nowhere - like at the fuel pump), so maybe it's still the same.
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Melting Slicks
Joined: Dec 2004
Posts: 3,285
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Hey Ron, I'm not good with this HVAC stuff.....but I remember over at the netreg site there is a "Loss of Logic" how to by Gordon....if I'm not mistaken.:o
It's either in the common issues section or the other maintenance chart section, maybe it's the "How To" section. May want to check it out as it may be of some use.
Tom
http://www.zr1netregistry.com/ZR1_issues.htm#19 This the thing by Gordon I was talking about.
It's either in the common issues section or the other maintenance chart section, maybe it's the "How To" section. May want to check it out as it may be of some use.
Tom
http://www.zr1netregistry.com/ZR1_issues.htm#19 This the thing by Gordon I was talking about.
Last edited by tomtom72; Mar 22, 2008 at 04:03 PM.