HVAC Temperature control not working
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
Likes: 0
From: Tahlequah OK
HVAC Temperature control not working
Hello folks! This is my first post so excuse me if I do something wrong. I have a 98 Coupe that I purchased back in April. The car was very well maintained with only 61K on it. It has the automatic HVAC system and has worked perfectly until a few days ago. Now, you can only adjust the temperature up or down in one degree increments. You have to wait for the SET light to go off and then you can bump it another degree. It will not enter the auto mode, hitting the off button does nothing, and the front defrost button does nothing. The rear defrost works fine and the fan speed can be adjusted manually. The A/C can be turned on and off.
I have read here on the forum and came up empty handed. I have cleaned both of the grounds behind the headlights, checked the fuses, etc. with no change in symptoms. I removed the battery and really don't see any significant leakage issues. I thought someone here might have experienced the same problem and could point me in the right direction. Thanks in advance for any and all help! Henry
I have read here on the forum and came up empty handed. I have cleaned both of the grounds behind the headlights, checked the fuses, etc. with no change in symptoms. I removed the battery and really don't see any significant leakage issues. I thought someone here might have experienced the same problem and could point me in the right direction. Thanks in advance for any and all help! Henry
Drifting
Joined: Oct 2004
Posts: 1,591
Likes: 1
From: San Jose CA
And if the other suggestions don't work sounds like your HVAC unit is going bad and needs to be replaced (IMO). See my post #4 here:
http://forums.corvetteforum.com/show....php?t=1872157
Good Luck,
- Eric
http://forums.corvetteforum.com/show....php?t=1872157
Good Luck,
- Eric
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
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From: Tahlequah OK
Thanks for the help! Checking the codes was next on my list. I did and here's what I found:
PCM - No Codes
TCS - C1255H
RTD - No Codes
BCM - No Codes
IPC - No Codes
Radio - No Codes
HVAC - No Codes
LDCM - B2282H, B2284H, U1064H
RDCM - B2283H, B2285H, U1064H
SCM - B0851H
RFA - No Codes
I cleared all the codes and took it for a test drive. At first, everything was working normal except I could still only change the temperature one degree at a time. Auto mode worked, front defrost worked, etc. But .... after about 5 miles, it went back to the way it was. No auto mode, off button doesn't work, front defrost not working, etc.
When I got home, I checked the codes again and all of them read "No Codes". Any ideas???
PCM - No Codes
TCS - C1255H
RTD - No Codes
BCM - No Codes
IPC - No Codes
Radio - No Codes
HVAC - No Codes
LDCM - B2282H, B2284H, U1064H
RDCM - B2283H, B2285H, U1064H
SCM - B0851H
RFA - No Codes
I cleared all the codes and took it for a test drive. At first, everything was working normal except I could still only change the temperature one degree at a time. Auto mode worked, front defrost worked, etc. But .... after about 5 miles, it went back to the way it was. No auto mode, off button doesn't work, front defrost not working, etc.
When I got home, I checked the codes again and all of them read "No Codes". Any ideas???
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
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From: Tahlequah OK
Eric,
Sounds similar except the display and back lights all work fine. What is the "resistor / solder" thing you mentioned? And if I do have to replace the part, what's it called and how do I contact Gene Culley?
Thanks,
Henry
Sounds similar except the display and back lights all work fine. What is the "resistor / solder" thing you mentioned? And if I do have to replace the part, what's it called and how do I contact Gene Culley?
Thanks,
Henry
Drifting
Joined: Oct 2004
Posts: 1,591
Likes: 1
From: San Jose CA
http://forums.corvetteforum.com/show....php?t=1872552
The "resistor/solder thing" was where you had the LCD display fade, as in you can barely read the digital readouts. To resolve this, there is a post somewhere on this forum (might want to do a search on "HVAC" and "resistors" or check the DYI's at the top of the forum -- I think its there) where you add more solder to a couple of resistors inside/back of your HVAC (you have to pull your HVAC out and open it up) -- basically the soldering from the factory wasn't that good, for lack of a better word, and by doing this the screen will brighten up the way its supposed to.
Good luck,
- Eric
Le Mans Master
Joined: May 2007
Posts: 5,383
Likes: 6
From: hagerstown md
St. Jude Donor '08-'09
Here's the link to thepart you need from Gene. It is definately your controller, otherwise you would be throwing codes.
http://www.trademotion.com/partlocat...layCatalogid=0
http://www.trademotion.com/partlocat...layCatalogid=0
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Drifting
Joined: Oct 2002
Posts: 1,774
Likes: 66
From: SoCal
Or look online for a used one. I picked one up for $120 shipped on here a month ago.
Here is another possible one. Try this guy.
http://forums.corvetteforum.com/show...highlight=HVAC
Here is another possible one. Try this guy.
http://forums.corvetteforum.com/show...highlight=HVAC
Last edited by RedRiderZR1; Nov 26, 2007 at 03:29 PM.
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
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From: Tahlequah OK
Thanks for the help guys! Eeek! $304 for the one for my 98. So ... how difficult is it to swap out this part? Does the bezel around the control pannel and radio snap off so you can get to it? Any tips or tricks would be appreciated.
Drifting
Joined: Oct 2002
Posts: 1,774
Likes: 66
From: SoCal
Look around more. Seen them for $250 new before I bought mine. As far as the surround it is easy.
http://www.vetteessentials.com/instr...zel_howto.html
Step 2A to 3F
http://www.vetteessentials.com/instr...zel_howto.html
Step 2A to 3F
Drifting
Joined: Oct 2004
Posts: 1,591
Likes: 1
From: San Jose CA
http://www.vetteessentials.com/instr...brake_h_b.html
There are other places on this forum that have similar instructions. Its easier than it looks. The HVAC itself is held in with two screws (front), a set of cables (tie wrapped) in the back...just unscrew and disconnect the cables and swap in the new unit.
Yeah I know, $300 bills for an HVAC is quite a bit. However compared to the dealer its a deal (I think they wanted $500+). Plus I was dickering around with codes, checking the connectors, etc (similar to what you are doing now) and I think I removed the bezel/checked the HVAC cabling like 2 two times before I ended up replacing the whole thing.
Wish I could have those extra hours back.... 
Good luck,
- Eric
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
Likes: 0
From: Tahlequah OK
You guys are great! Thanks so much for the help. I found a guy on eBay that has an exchange service for all kinds of electrical stuff. He has brand new ones for $190 and repaired ones for $100. He has tons of feedback and it's all positive. Anyone ever used this guy? Do a search for item #270190197077. His user name is digital_dash_solutions.
Le Mans Master
Joined: May 2007
Posts: 5,383
Likes: 6
From: hagerstown md
St. Jude Donor '08-'09
You guys are great! Thanks so much for the help. I found a guy on eBay that has an exchange service for all kinds of electrical stuff. He has brand new ones for $190 and repaired ones for $100. He has tons of feedback and it's all positive. Anyone ever used this guy? Do a search for item #270190197077. His user name is digital_dash_solutions.
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
Likes: 0
From: Tahlequah OK
Thanks to everyone for all of the advise and links. I have a new control ordered. I ended up buying it from thepartsladi for $10 more but I don't have to send in the old control unit. While checking around to make sure I got the right control, I found RockAuto.com. They actually give you the part number and it's easy to navigate. Thanks again! Henry
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
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From: Tahlequah OK
Thought I'd give you folks an update. I got the new control head yesterday and got it installed today. 20 minutes to switch it out thanks to the vetteesentials website and their detailed instructions. It was like I had done it a dozen times before. $210 total for a brand new unit and 20 minutes of labor. Thanks again for all the help! Henry
,,,,how does it work??????????
Just busting on you!
Thread Starter
8th Gear
Joined: Nov 2007
Posts: 8
Likes: 0
From: Tahlequah OK
Yes, everything works 100% now plus with the new part, I have a 2 year warranty. If any of you are hesitating to swap out your unit, go for it. Even the mechanically challenged could do this easy enough.
