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Alright guys and gals, I have a 2003 C5. It's been my everyday driver for the last couple of years. One day I get in the car and the HVAC controls won't come on, so no AC. Out of the blue, never got dim never fluttered worked one day, and the next didn't and hasn't since. Nothing comes on. SO I read the forums and figured it was my resistors on the back. First I checked all the fuses, everything looks good then Took the HVAC out, soldered the resistors on the back. Still nothing. SOOOO, maybe I was a crappy solderer. Bit the bullet and bought a new (to me) HVAC, installed it. You guessed it, still nothing. Now I know it can't be the resistors. I've tried everything. Getting the HVAC No Comm code and also have a code for ABS and OS sensor. Not sure on the exact codes can get them if that would help. I know my check engine light is on for O2 sensor and lights are on for ABS and Traction Control. Any other ideas before I send it to a shop to charge me an arm and a leg??
For an HVAC “no comm” you should check the modules power and ground…don’t know if you have any electrical testing experience with a DVOM so I won’t go any further with what to check...also let us know what the other DTC's are !!...with the HVAC and ABS (EBCM) and O2 HEATER circuit DTC this could be a bad ignition switch...one of the 4 wires from the ignition switch that energize the circuit that these 3 items are on. Are your O2 codes either a P0135, 0141, 0155, or 0161 ???
Thank you for a speedy reply..... okay the DTC's I'm getting are: P0135, P0141. P0155, P0161, P01571 H C, P01689 H C. TCS: No Comm. BCM: B0432 H C. SDM: U1040 H C. HVAC No Comm.
Seems like a lot of codes lol! Nailed all the codes you mentioned!
Thank you for a speedy reply..... okay the DTC's I'm getting are: P0135, P0141. P0155, P0161, P01571 H C, P01689 H C. TCS: No Comm. BCM: B0432 H C. SDM: U1040 H C. HVAC No Comm.
Seems like a lot of codes lol! Nailed all the codes you mentioned!
I have been throwing these codes for awhile before HVAC went out. Could it still be related?
Yes !!…if you have a DVOM we can verify the diagnosis by doing a voltage drop check across the ignition switch…basically we check the voltage at the battery and then at the O2 heater circuit fuse…if you have 12 volts at the battery but 8 volts coming to the fuse we have a 4 volt voltage drop through the switch…with key on connect one lead of the DVOM to battery positive and the other DVOM lead to either test point on top of fuse 15…read the voltage and don’t worry if it shows plus or minus…if it says minus you would just swap leads !!…also you may have to clear the O2 codes before testing.
Yes !!…if you have a DVOM we can verify the diagnosis by doing a voltage drop check across the ignition switch…basically we check the voltage at the battery and then at the O2 heater circuit fuse…if you have 12 volts at the battery but 8 volts coming to the fuse we have a 4 volt voltage drop through the switch…with key on connect one lead of the DVOM to battery positive and the other DVOM lead to either test point on top of fuse 15…read the voltage and don’t worry if it shows plus or minus…if it says minus you would just swap leads !!…also you may have to clear the O2 codes before testing.
Okay, tried this and I’m reading 12V to the O2 heater circuit fuse. What now??? Also tested fuse #24 (A/C) and wasn’t getting any readings on it.
Okay, tried this and I’m reading 12V to the O2 heater circuit fuse. What now??? Also tested fuse #24 (A/C) and wasn’t getting any readings on it.
So you tested between battery positive and the O2 heater fuse with a multimeter and you see 12 volts ??…if you see 12 volts this means you are dropping ALL of the battery voltage across the switch…you should only see .1 to .2 volts. How EXACTLY did you test the AC fuse ??…did you use a multimeter or a test light ??
So you tested between battery positive and the O2 heater fuse with a multimeter and you see 12 volts ??…if you see 12 volts this means you are dropping ALL of the battery voltage across the switch…you should only see .1 to .2 volts. How EXACTLY did you test the AC fuse ??…did you use a multimeter or a test light ??
So I have an older model multimeter. This is my first time using it so I quite possibly did it wrong. Anyways, it has a black negative wire with a clamp and a red positive wire with a pinpoint. I turned the analog to read 0-50 DC on the multimeter then I put the red pinpoint on the positive terminal of the battery and was able to get the black clamp to touch the top of the fuse. This is when it read 12v.. I did the same ting to fuse 24 and read 0v. I flipped it and put the black clamp on the battery and touched the red pinpoint to the fuse and it went negative but its older analog style so nothing comes before 0. Thanks for all the help so far. Im still learning!!
So I have an older model multimeter. This is my first time using it so I quite possibly did it wrong. Anyways, it has a black negative wire with a clamp and a red positive wire with a pinpoint. I turned the analog to read 0-50 DC on the multimeter then I put the red pinpoint on the positive terminal of the battery and was able to get the black clamp to touch the top of the fuse. This is when it read 12v.. I did the same ting to fuse 24 and read 0v. I flipped it and put the black clamp on the battery and touched the red pinpoint to the fuse and it went negative but its older analog style so nothing comes before 0. Thanks for all the help so far. Im still learning!!
Well this is my voltage drop check…battery positive to O2 heater fuse with key ON…I’m seeing 0.13 volts…did you check both test points or removed it and made sure it wasn’t blown or checked it with the meter ??…if you’re showing 12 volts zero voltage is getting across the switch…if I were you I’d take a crash course in electrical testing or find yourself a good “auto electric” shop in your area that you can trust…with these cars getting 20 years old you WILL have problems down the road !!…if you can buy yourself a decent DVOM. If you decide to change your switch you can get an AC Delco on Rock Auto…that’s where I got mine a few years ago.
Well this is my voltage drop check…battery positive to O2 heater fuse with key ON…I’m seeing 0.13 volts…did you check both test points or removed it and made sure it wasn’t blown or checked it with the meter ??…if you’re showing 12 volts zero voltage is getting across the switch…if I were you I’d take a crash course in electrical testing or find yourself a good “auto electric” shop in your area that you can trust…with these cars getting 20 years old you WILL have problems down the road !!…if you can buy yourself a decent DVOM. If you decide to change your switch you can get an AC Delco on Rock Auto…that’s where I got mine a few years ago.
Okay, I just pulled the fuse then tested both sides in the relay box... one side read 12V and the other 9V.... This picture is with the fuse in but just to show what my multimeter looks like. lol The right side of the fuse, (one im touching in pic) is the side that reads 12v if I pull the fuse and touch the left side, down in relay box, it reads 9v whereas the right side still reads 12v with the fuse pulled...
Not necessary to pull the fuse out and check voltage drop down in the box…if you just did it the way I told you that’s good enough !!…if you want to get a second opinion on the diagnosis feel free to take it to a shop…good luck my friend !!…that multimeter must be older than me and I’m old…LOL !!
Going to order a new ignition switch tomorrow and hopefully install it this week and see if that resolves the issues! I will keep you posted! Thanks for the help!
Going to order a new ignition switch tomorrow and hopefully install it this week and see if that resolves the issues! I will keep you posted! Thanks for the help!
The only thing you have to know is how to remove the lock cylinder from the switch...pic is from the FSM.
Not necessary to pull the fuse out and check voltage drop down in the box…if you just did it the way I told you that’s good enough !!…if you want to get a second opinion on the diagnosis feel free to take it to a shop…good luck my friend !!…that multimeter must be older than me and I’m old…LOL !!
The only thing you have to know is how to remove the lock cylinder from the switch...pic is from the FSM.
New ignition switch installed. HVAC is working!!! Check engine light is off, ABS/EBCM light still on but I’ll worry about that another day! AC feels good! Thanks!!
HVAC not working
