Will Anyone with Electrical Knowledge help me?
Thread Starter
Pro
Joined: Feb 2011
Posts: 565
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From: Broussard Louisiana
Will Anyone with Electrical Knowledge help me?
I am having trouble tracking down what the problem is with my A/C not coming on still. The only code I'm getting is "• DTC B0432 Rear Defogger Relay Circuit" The control for the rear defogger is on the A/C Controller so I figure this must be at least part of the problem. I changed the relay for the Defogger and it didnt help. I have started cleaning all the chassis Grounds as I find them from an article i read about grounding issues and the little plugs being corroded but so far none i take apart have any corrosion on or In them. Does anyone know which Chassis Ground the A/C Control would be connected too? Ive done the one under the battery Box,and the two by the Headlights.
In case you havent read my previous thread, The A/C acts like there is no power going to the controls...Every now and then when i start the car the A/C will come on but when i kill the car and start it back again the a/c does nothing...the Blower doesnt blow, the lights in the control dont come on or anything. I have the old type controls not the digital and not the adjustable side to side type. thanks for any help, I need this thing to work its in the 100's here in the day and it is bad.lol
In case you havent read my previous thread, The A/C acts like there is no power going to the controls...Every now and then when i start the car the A/C will come on but when i kill the car and start it back again the a/c does nothing...the Blower doesnt blow, the lights in the control dont come on or anything. I have the old type controls not the digital and not the adjustable side to side type. thanks for any help, I need this thing to work its in the 100's here in the day and it is bad.lol
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Mark
The very FIRST thing that you need to do is get a DC Volt Meter and find all the fuses for the HVAC controller head.
Mini Fuse 18, 27 and 49 in the Instrument Panel ELECTRICAL CENTER...
Make sure that the fuse is good AND there is voltage on each one of those fuses by measuring the fuse test points on top of the fuse to ground....
Make sure that the key is ON for fuse 18
BC
The very FIRST thing that you need to do is get a DC Volt Meter and find all the fuses for the HVAC controller head.
Mini Fuse 18, 27 and 49 in the Instrument Panel ELECTRICAL CENTER...
Make sure that the fuse is good AND there is voltage on each one of those fuses by measuring the fuse test points on top of the fuse to ground....
Make sure that the key is ON for fuse 18
BC
Team Owner
Joined: Jul 2006
Posts: 22,188
Likes: 4,178
From: Kannapolis NC
I'm not a C5 manual control expert, but I do have some electrical background. It would be rare to have a fuse bad that would be good sometimes and bad others. Possible, but very rare that it could be broken and not blown. I would try to measure the voltage on the HVAC fuse when it works and when it doesn't to see if any voltage is missing, but it will probably be on both sides of the fuse if it is. My first troubleshooting would be to pull out the controller and check closely the pins on both sides of the connector plugs. If you start the car and it's not working, wiggle the wiring and try to find out what makes it work. If the lights on the controller are also not working as you say, you may be losing connection completely at one of the connector plugs. The voltage for the lights and for a/c operation is a different voltage from a different source. Bill would know better whether the ignition switch could be intermittent causing this, he did a great writeup on fixing the switch. But, again, if the lights aren't working when the a/c isn't, it sounds like you're losing a connection to the whole controller.
Pro
Joined: Oct 2009
Posts: 560
Likes: 3
From: Centennial Colorado
The ground you are looking for is G203 at the base of the right "A" pillar.
Fuses to check at the Instrument Panel Electrical Center:
Fuse 27-10amp- hot at all times - HVAC CON Mini
Fuse 18-10amp-hot in RUN - HVAC Mini
Fuse 49-30amp-hot at all times - BLO MOT Maxi
Stuff to check on HVAC harness:
Check power on the red wire (B) on C2 at the hvac control head with the key on, and off. You should get 12vdc on that pin with the key on, and lose it with the key off. If G203 is good, you've just verified fuse 18 and the Blower Motor Relay which feeds the hvac controller.
Check power on the Orange wire (E) on C1 at the hvac control head. Wire is HOT at all times. If good, you've verified fuse 27.
Check power on the Brown wire (C) on C1 at the hvac control head. Wire is HOT in RUN, and is fed from fuse 18.
Check for Ground on Black wire (K) on C1.
The rest of the HVAC Harness wiring goes to the PCM, Blower Motor Control Module (behind right dash), and the Temperature Door Motor (behind dash on heater plenum).
There is more to it then this, but it should give you a start.
-Jeff
Fuses to check at the Instrument Panel Electrical Center:
Fuse 27-10amp- hot at all times - HVAC CON Mini
Fuse 18-10amp-hot in RUN - HVAC Mini
Fuse 49-30amp-hot at all times - BLO MOT Maxi
Stuff to check on HVAC harness:
Check power on the red wire (B) on C2 at the hvac control head with the key on, and off. You should get 12vdc on that pin with the key on, and lose it with the key off. If G203 is good, you've just verified fuse 18 and the Blower Motor Relay which feeds the hvac controller.
Check power on the Orange wire (E) on C1 at the hvac control head. Wire is HOT at all times. If good, you've verified fuse 27.
Check power on the Brown wire (C) on C1 at the hvac control head. Wire is HOT in RUN, and is fed from fuse 18.
Check for Ground on Black wire (K) on C1.
The rest of the HVAC Harness wiring goes to the PCM, Blower Motor Control Module (behind right dash), and the Temperature Door Motor (behind dash on heater plenum).
There is more to it then this, but it should give you a start.
-Jeff
