I just got a '92 Coupe and one of the problems is that the blower fan does not come on. I have tried every setting, hot or cold, manual or automatic fan speed, etc. and cannot get it to come on. The module in the dash seems to be working correctly and I can hear the engine fan come on when I call for AC, so it seems to be signaling the PCM correctly.

I read the codes as per the instructions on this page: http://www.idavette.net/tech/c4diag.htm and got the following results. During this troubleshooting, I had the car idling in park and the requested temperature set all the way down (15c/60f), the main bank of flow controls set to "auto", and the fan speed control set to "auto" as well. The outside temperature was reported as 17c/63f, which seems reasonably correct.

HVAC Diagnostics:

0 - System Faults: 07 = Solar Load Sensor Open

1 - Temp Setting: 64

2 - In-Car Temp: 85

3 - Outside Temp Sensor: 106

4 - Sun Load Sensor: -140 (240?)

5 - Ignition System Voltage: 196

6 - Engine Speed: 26 to 28

7 - Vehicle Speed: 00

9 - A/C System Mode: 01 (Re-circulation?)

10 - Blower PWM: 127 (Almost 14V?)

11 - Program Number: 00 (Cold?)

12 - Mix Number: -155 (255)

16 - Coolant Temp: 92 (degrees celcius)

17 - Solar Correction: 128 (max light)

19 - ???: 122
20 - ???: 84
21 - ???: 144
22 - ???: 197
23 - ???: 128
24 - ???: 128

30 - Stored Full Hot Value: 48

31 - Temp Door Travel Range: 164

34 - Temp Door Position Requested: -153 (253) Full Cold

35 - Compressor On Time: Went from 10 to 188 fairly quickly, then back to 00

36 - Number Of Times Below Critical Time: 00

37 - Software Version Number: 00

Would the 07 - Solar Load Sensor Open cause the blower fan not to come on, or just force the system to use a default value. Is there anything else in these results that points to the problem? The previous owner says he removed and bench tested the blower motor and that it works, and that he thinks it's the resistor. Sorry for the essay, but I wanted to do all of the homework I could before asking for help. Any input would be appreciated before I start pulling things apart.

Thanks

 

The first step seems to try to run the fan directly from a separate 12v supply/battery. (You will need a good connection since the fan takes about 20 amps at 12 volts). The fan connector is reasonably easy to access.

If the fan runs, then the second suggestion is to check the resistor pack located at the top of the evaporator case.

 

I took a quick look at the car and found what I think is the "resistor pack", it's labeled with part # 52470337 which isn't the part listed for my car. The dealer found a listing for a "blower control module" in his computer, but it's a couple weeks away and he wants $333.36 for it. Should I grab another 52470337 from the wreckers (ie. are they interchangeable?) or bite the bullet and get the "correct" part number from the dealer? Is there any way to test these modules?

 

A suggestion is that you get the GM/Helms manuals (electrical and mechanical). It will cost way less that $334, and it may help you find the problem. For instance, for 1995, there is a whole page troubleshooting flow chart (8A-66-3) titled - 'Blower motor will not run in any mode'.

After this fix for the blower, the manual will likely pay for itself a few more times.

My thoughts are to not spend that kind of money until you are more sure which part is bad.

There is a blower motor fuse too that the manual suggests should be checked as well.

Not likely in this case, but the manual also mentions checking the A/C PROG fuse, and the AC Clutch fuse.

 

I'm trying to track one down for an affordable price. I was hoping to find a .pdf file of the manual to download just to get me started until I receive the paper version, but I haven't had any luck there. I'm sure the manual will come in quite handy as there are quite a few little issues to resolve.


Thanks. I checked all of the fuses in the fuse box by the passengers door. I'm not sure if there are other fuses hidden in the car, but I guess I'll have to wait and find a copy of the factory manuals before fixing this.

 

There is also a 30 amp blower fuse behind the battery in the engine compartment. If your car has the automatic climate control (C68) the blower module is what you see on the evaporator housing. The dealer price sounds ridiculous, even Ecklers lists it much cheaper. http://www.ecklers.com/corvette-blow...1990-1992.html
The Owners Manual may be available on-line in PDF format but I have never seen the service manual. As mentioned the FSM is a your best bet, it includes a troubleshooting chart for your problem. Here is a link to a low cost set if you can live with cosmetic issues.
http://tinyurl.com/3a283cc
Another option is Alldata, a subscription for your car will provide access to the FSM, TSB's and lots of other helpful info. Not as convenient as a paper copy but a real bargain at less than $30 http://www.alldata.com/

 

With the shipping charges being so high on beat up ebay manuals, I broke down and bought new ones straight from Helms. I'll get the Haynes as well just to get me through until the FSMs arrive.

If I wanted to try replacing the module, it looks like a number of Oldsmobiles and Cadillacs have a part that looks the same to my eye, with the same connectors. Would it be safe to head to the wreckers and try one of these modules, even if the part number doesn't line up with what GM says it should have?

 

first, check the blower motor to see if it isn't burned out. Jumper it with a wire using a fuse holder with a 25 amp fuse in it.
If the blower runs, look for bad ground, etc. prior to making your troubleshooting difficult by following everybody's instructions.
Service manual is the instructions you should follow.

 

As suggested, jumper directly to battery to make sure the Motor is good. Examine the Connector looking for melted wires which would be indicative of a voltage drop caused by a bad connection. The terminals are crimped and sometimes need to be soldered to the leads. You'll have to take apart the weatherpak to view the crimps.

Electronic Air uses the Blower Module which amplifies low voltage signals from the Processor - the Programmer - to run the Blower Motor. The Programmer gets it's signals digitally or over a serial data line from the Dash Controls. The Blower signal at the Module is on the Tan or Dark Brown wire with a range of around 2.5 (1) to 6 volts (10). The output is on the Purple (or whatever is hot at the Blower) with a range of 4 to 12 volts. If it has the input voltage and no output it's the Blower Module. If it doesn't have the input, it's usually the Programmer. That's easier to troubleshoot with a Bi-directional scanner through the Body Module (CCM) link. The Scanner emulates the Controls and if it all works, it's the Controls. If it still doesn't work, it's the Programmer.

 

The previous owner told me he checked the motor, but I will do it again just to be sure. I just have to make a good set of test leads including a ground as there's never anywhere to ground to when checking stuff on this car.

Thanks so much, that's the kind of info I was looking for in order to get me by until my factory service manual arrives. That gives me something to work on this weekend and a hope of fixing my air without waiting weeks for my manual to arrive from Helms.

btw, I bought the Haynes manual last night hoping it would be just enough info to get me through until I get my FSM, and I have never seen a less helpful service manual in all of my life. All of the instructions, photos, and diagrams are generic and supposed to represent a "typical" corvette. There are only a handful of wiring diagrams on the back, and they too are "generic". It may be useful as as a quick reference for torque specs etc, but other than that it was a waste of $30.

 

In a pinch, I think Alldata - www.alldata.com - is a tad better than Haynes.

You're going to want to fix that Sun Load error too as it's used to control Blower Speed and Temp Door position for all settings but Auto 60 or 90. Remove the Connector and check for the reference signal which is either going to be 5 or 12 volts. Check resistance across the Sensor and if it reads infinity or open, you need a new Sensor.

 

Thanks for your help SunCR. With your info I was able to narrow the problem down to the module, and I found one in the wrecking yard today from a '91 Cadillac that fit and works perfectly. I still have to find a sun load sensor and replace the blower (cracked fan), but at least my A/C works now.

Thanks again.