2007 HVAC Lighting Issue Fix
Thread Starter
Senior Member
Scikotics
SL Member
Joined: Nov 2004
Posts: 9,731
From: Minneapolis, MN
2007 HVAC Lighting Issue Fix
Background of Issue
Many of the early 2007 tC's have had issues with the HVAC lighting working intermittently or stopping all together. If your HVAC lighting only works sometimes, goes out when the headlights are turned on, etc, this is probably your issue. If the car is under warranty and the dealer is going to fix it, they simply replaced the HVAC unit. However, those that are out of warranty or have done an LED swap probably arent always so lucky. The remaining alternatives have been either buying a new HVAC (around $500) or purchasing a salvaged one ($50 - $100).
The Fix
I was finally able to get one of these sent to me that I could plug into a test harness and test. I spent some time mapping out more of the lighting control circuit (I had mapped a good amount of it previously during design of the LED mod for the HVAC, but not the input and dimmer control portion) and found the issue. I have since had one other person try this fix on theirs successfully as well, so while this may not be the only possible cause, chances are this is the one causing the common issue. The issue is a couple of cold solder joints on the legs of one device. The fix is detailed below.
1) Remove the HVAC. There are plenty of threads and DIY writeups on the forums detailing this part, so I wont add all of that here.
2) Remove the HVAC from the housing so you have the bare board.
3) Locate T302 on the front of the board right under the hazard button. This is a 3 legged device (a transistor) that controls part of the lighting function.
4) With a low power soldering iron with the tip tinned just a tad, reheat the solder joints on each of the three legs so the solder reflows.
5) While you are at it, go ahead and check T303 right next to it.
6) Plug it in and test. The lighting should now act as normal!
A pic is provided below for reference. If you have any questions on this or have the issue and this fix does not work for it, feel free to contact me on the forums regarding it. Going forward, I will check every 07 HVAC that I perform led mods on for this and resolder the device for good measure to prevent the issue from popping up.
Many of the early 2007 tC's have had issues with the HVAC lighting working intermittently or stopping all together. If your HVAC lighting only works sometimes, goes out when the headlights are turned on, etc, this is probably your issue. If the car is under warranty and the dealer is going to fix it, they simply replaced the HVAC unit. However, those that are out of warranty or have done an LED swap probably arent always so lucky. The remaining alternatives have been either buying a new HVAC (around $500) or purchasing a salvaged one ($50 - $100).
The Fix
I was finally able to get one of these sent to me that I could plug into a test harness and test. I spent some time mapping out more of the lighting control circuit (I had mapped a good amount of it previously during design of the LED mod for the HVAC, but not the input and dimmer control portion) and found the issue. I have since had one other person try this fix on theirs successfully as well, so while this may not be the only possible cause, chances are this is the one causing the common issue. The issue is a couple of cold solder joints on the legs of one device. The fix is detailed below.
1) Remove the HVAC. There are plenty of threads and DIY writeups on the forums detailing this part, so I wont add all of that here.
2) Remove the HVAC from the housing so you have the bare board.
3) Locate T302 on the front of the board right under the hazard button. This is a 3 legged device (a transistor) that controls part of the lighting function.
4) With a low power soldering iron with the tip tinned just a tad, reheat the solder joints on each of the three legs so the solder reflows.
5) While you are at it, go ahead and check T303 right next to it.
6) Plug it in and test. The lighting should now act as normal!
A pic is provided below for reference. If you have any questions on this or have the issue and this fix does not work for it, feel free to contact me on the forums regarding it. Going forward, I will check every 07 HVAC that I perform led mods on for this and resolder the device for good measure to prevent the issue from popping up.
Thread Starter
Senior Member
Scikotics
SL Member
Joined: Nov 2004
Posts: 9,731
From: Minneapolis, MN
No, that is actually just a random pic of an 07 board I had 
Yours actually did not have the issue, but I did check for it and made sure those solder connections were good before I put yours back together 
Yours actually did not have the issue, but I did check for it and made sure those solder connections were good before I put yours back together
Senior Member
SL Member
Team ScioNRG
Joined: Oct 2006
Posts: 1,634
YEEEEEESSSSSS im selling my car and wanted to fix this. Mine used to come on if i did the old Fonzi slam on the side. Finaly it just stoped all together so im gunna try this and see how it comes out.
Thread Starter
Senior Member
Scikotics
SL Member
Joined: Nov 2004
Posts: 9,731
From: Minneapolis, MN
Will be catching up on PMs and emails soon everyone. I had to work all day today and have had a 102 temp all day as well. Caught a nasty flu from someone apparently.
Glad the fix worked again. Looks like this is the one for sure.
Glad the fix worked again. Looks like this is the one for sure.
Total sweetness Dave. Great work. Just got in an 07that I swapped about 2 years ago that came up with this issue. Sure enough, picked at T302 and it simply poped off without any effort. Soldered her back in place and BAM! LIGHT! Again countless thanks for this stellar find!
Member
Joined: Aug 2007
Posts: 47
From: Long Island, NY
about 6 months ago mine stopped working and I was convinced it was the PIAA head lights that I installed. I never realized it was such a widespread issue among the 07. The dealer ordered me a new HVAC unit, which was $800 and change that the warrenty covered....but I have to pay (according to my extended warrenty) a $50 deductible which is BS and I'm gonna try to get out of.