C5 Climate Control dim/dark display fix
Cruising
Joined: Apr 2010
Posts: 11
Likes: 0
Wow!! 
Thanks for the great FIX. Although when I see circuit boards my short hairs stand up but I've soldered before and worked with boards in the past so I should be able to take care of this. I'll work on it and let you know the outcome. Great rundown and thanks again.
Thanks for the great FIX. Although when I see circuit boards my short hairs stand up but I've soldered before and worked with boards in the past so I should be able to take care of this. I'll work on it and let you know the outcome. Great rundown and thanks again.
1st Gear
Joined: Apr 2010
Posts: 1
Likes: 0
this fix was excellent
thanks so much for this forum..fixed my control unit..removed and took it to a great auto-stereo shop..soldered it for $20..works great..loved saving the cash..also on this forum was some great advice for changing front turn signal bulb..dealer wanted $130...cost me about $5 for TWO bulbs..lovin it...P.S. while console was removed had the show wire in an IPOD jack to the radio and into the console for $150..am really pleased...thanks again..
Instructor
Joined: Jun 2002
Posts: 111
Likes: 0
From: Chesapeake Va
Fixing the resistors
I just completed this repair and wanted to share some info. I have the second variation with 8 241 SMD in the center. They are in parallel an the outside of each resistor is connected to each other, and same for inside.
By using a meter, I touched an outside resistor between the board and the resistor, then touch the top of the remaining resistors lightly with the probe to ensure each read zero ohms. If you had an area fluctuate then press harder with the probe and see if it goes to zero ohms. If so that is a bad joint.
Then go to the inside and test each joint in the same manner.
Turns out I had two bad joints and resoldered them. I did not use additional solder, instead, I pressed the resistor down with a tool, and then applied the solder iron for a short period to resolder the joint. Seems to have worked fine, with no distortion to the board lacquer.
I think the board flexs too much and the solder joints are not as good as most of the other components on the board.
My unit would work early when car was cooler, and not work when hot.
Great thread! G
By using a meter, I touched an outside resistor between the board and the resistor, then touch the top of the remaining resistors lightly with the probe to ensure each read zero ohms. If you had an area fluctuate then press harder with the probe and see if it goes to zero ohms. If so that is a bad joint.
Then go to the inside and test each joint in the same manner.
Turns out I had two bad joints and resoldered them. I did not use additional solder, instead, I pressed the resistor down with a tool, and then applied the solder iron for a short period to resolder the joint. Seems to have worked fine, with no distortion to the board lacquer.
I think the board flexs too much and the solder joints are not as good as most of the other components on the board.
My unit would work early when car was cooler, and not work when hot.
Great thread! G
Advanced
Joined: May 2010
Posts: 65
Likes: 0
From: Contrecoeur Québec
Thanxs to all who contributed to this thread. My display was also dead, its the second generation kind, and I couldn't see anything wrong with any of the 241 chips, even with a magnifying glass. They were not loose or moved at all...
I redid all the joints using a bit of flux to help the solder, did not add any extra. Works like new!
It was a good opportunity to clean all the buttons in there as well. Looks like a large french moka coffee ended up in there!
I redid all the joints using a bit of flux to help the solder, did not add any extra. Works like new!
It was a good opportunity to clean all the buttons in there as well. Looks like a large french moka coffee ended up in there!
Melting Slicks
Joined: Nov 2004
Posts: 3,495
Likes: 0
From: Paducah Ky
Add 1 more happy camper too the list.
Mine had been going dim lately and then nothing. Came across this thread and honestly was hoping there was an easier fix, but since I had put a B&M shifter several years ago I did know I could do part of it. I believe the hardest part was pulling the power cord out of the back, man that sucker was in there.
I've never had a solder iron in my hands until this afternoon, just took my time and hallelujah it worked!!! Sure is nice to have it back working again. Thanks for the thread!!
Mine had been going dim lately and then nothing. Came across this thread and honestly was hoping there was an easier fix, but since I had put a B&M shifter several years ago I did know I could do part of it. I believe the hardest part was pulling the power cord out of the back, man that sucker was in there.I've never had a solder iron in my hands until this afternoon, just took my time and hallelujah it worked!!! Sure is nice to have it back working again. Thanks for the thread!!
2nd Gear
Joined: May 2010
Posts: 2
Likes: 0
Bought my 98 three years ago and watched display fade out---was saving for a replacement when I started researching alternative repair sources....Pulled mind out last night and fixed it following suggestions on this site...Works great now. I used a 15 watt radio shack soldering iron with a pencil tip and a little flux and just a very very small amount of solder on the tip to help joint re-flow. Took longer to pull the unit out of the I/P than to fix the resistors. Thanks a lot. Saved a bundle.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Are there any soldered in components that affect the EXT TEMP display?
My ext temp reading is erratic - upon startup, it runs down to 15 or so then back up to about 20 degrees below true ambient. When I disconnect the sensor, the reading on the Dual control unit stays the same. So, I think the problem is inside the control unit.
This means that the AC doesn't work when the control unit reads below 34F. Gotta have AC in Texas in summer.....
I'm hoping that repairing a solder joint or two inside the unit will fix this.
Any ideas out there?
Thanks mucho.
My ext temp reading is erratic - upon startup, it runs down to 15 or so then back up to about 20 degrees below true ambient. When I disconnect the sensor, the reading on the Dual control unit stays the same. So, I think the problem is inside the control unit.
This means that the AC doesn't work when the control unit reads below 34F. Gotta have AC in Texas in summer.....
I'm hoping that repairing a solder joint or two inside the unit will fix this.
Any ideas out there?
Thanks mucho.
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Tech Contributor
Joined: Jan 2007
Posts: 19,471
Likes: 1,171
From: Dyer, IN
Are there any soldered in components that affect the EXT TEMP display?
My ext temp reading is erratic - upon startup, it runs down to 15 or so then back up to about 20 degrees below true ambient. When I disconnect the sensor, the reading on the Dual control unit stays the same. So, I think the problem is inside the control unit.
This means that the AC doesn't work when the control unit reads below 34F. Gotta have AC in Texas in summer.....
I'm hoping that repairing a solder joint or two inside the unit will fix this.
Any ideas out there?
Thanks mucho.
My ext temp reading is erratic - upon startup, it runs down to 15 or so then back up to about 20 degrees below true ambient. When I disconnect the sensor, the reading on the Dual control unit stays the same. So, I think the problem is inside the control unit.
This means that the AC doesn't work when the control unit reads below 34F. Gotta have AC in Texas in summer.....
I'm hoping that repairing a solder joint or two inside the unit will fix this.
Any ideas out there?
Thanks mucho.
You can also measure the resistance of the sensor itself, and compare it with the values in the service manual.
Last edited by lucky131969; Jun 1, 2010 at 03:41 PM.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
If you disconnect the sensor, the control panel will default to a set reading.....56 degrees if I recall.......so disconnecting it tells you nothing. The sensor is at a high resistance when the temperature is cold, and low resistance when warm/hot. If you are reading low ambient temps on the display, the there may be a high resistance connection at the plug, or high resistance to ground. I would evaluate the resistance to ground at pin B(Gray/black stripe wire), and check for 5 volts at pin A(light green/black stripe wire).
You can also measure the resistance of the sensor itself, and compare it with the values in the service manual.
You can also measure the resistance of the sensor itself, and compare it with the values in the service manual.
I read somewhere on the CF that the unit defaulted to 69F if the sensor is disconnected but that's not happening for me.
I'll check as you suggested.
Le Mans Master
Joined: May 2006
Posts: 5,987
Likes: 18
From: DuBois PA
St. Jude Donor '11-'12-'13-'14-'15
The HVACs I've benchtested all read 69, BUT that's without any BCM inputs or anything... So I wouldn't say for 100% that uplugging the sensor will place the external temp in defualt @ 69 degrees...
You're in excellent hands with Lucky... Listen and learn!
Tim
You're in excellent hands with Lucky... Listen and learn!
Tim
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
If you disconnect the sensor, the control panel will default to a set reading.....56 degrees if I recall.......so disconnecting it tells you nothing. The sensor is at a high resistance when the temperature is cold, and low resistance when warm/hot. If you are reading low ambient temps on the display, the there may be a high resistance connection at the plug, or high resistance to ground. I would evaluate the resistance to ground at pin B(Gray/black stripe wire), and check for 5 volts at pin A(light green/black stripe wire).
You can also measure the resistance of the sensor itself, and compare it with the values in the service manual.
You can also measure the resistance of the sensor itself, and compare it with the values in the service manual.
I have tried two replacement sensors.
At last startup, the DCC read -15F.
Any ideas appreciated.
Tech Contributor
Joined: Jan 2007
Posts: 19,471
Likes: 1,171
From: Dyer, IN
Also curious what resistance is measured at the sensor itself. According to the table, it should be around 7000-8000 ohms.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Does the low voltage mean the DCC unit is sending out a voltage that is too low for the sensor to work?
I'll check the sensor but I get the same result with two sensors - one several years old and one brand new - both GM parts.
Heel & Toe
Joined: Mar 2009
Posts: 22
Likes: 0
Hvac is Dim, but heat also does not work?
I bought the C5 with a already Dim HVAC. I have not had to use the Heat until the other night when the targa was off and it got cold out. I tried turning on the heat but nothing came out? I also tried using the A/C, but nothing again.
Does this have anything to do with the display unit or is it something else. I know it also was showing 169 degrees for outside temp on the display? Any input would be great.
Thank You
Does this have anything to do with the display unit or is it something else. I know it also was showing 169 degrees for outside temp on the display? Any input would be great.
Thank You
Cruising
Joined: Apr 2010
Posts: 11
Likes: 0
Thanks Relsek for the latest thread. I've been so busy that I haven't got around to fixing but I plan too real soon. Glad I asked the question and great forum. On another note I have a 79 and plan to change to a high performance shorter starter. I'd be interested to see if anyone has done that. Thanks again, Mark
1st Gear
Joined: Apr 2008
Posts: 1
Likes: 0
Worked for me too!
Thanks for posting tips like this, it saves us all a ton of hassle at the dealer and some $$$ too!
BTW, RadioShack does have 12V/60mA lamps still, but they only carry 3 packs (2 bulbs) per store. Had to hit 3 stores to get enough bulbs and they are not listed on their website.
I had both the dim display (fixed by resoldering the resisters) and the burnt out bulbs. Any original bulbs I had popped when I started replacing the bad ones. Its all good now!
BTW, RadioShack does have 12V/60mA lamps still, but they only carry 3 packs (2 bulbs) per store. Had to hit 3 stores to get enough bulbs and they are not listed on their website.
I had both the dim display (fixed by resoldering the resisters) and the burnt out bulbs. Any original bulbs I had popped when I started replacing the bad ones. Its all good now!