This is on an 86 with Electonic A/C (C68). The blower fan does not seem to work at any speed. I tried appliying 12v direct to the fan and it seems to work just fine.

I went thru the FSM and it had me probing the blower control module. The only problem is that the connector si not exactly like the diagram and I need to be sure I am doing the right thing. Does anyone have a better way or description of how to check this thing out?

It is mighty hot out here and I want my A/C back.

Thanks!

Dale

 

there is a resister pack thingy on the top of the evap box... has a bunch of wires going to it... that's where I think your problem is...

 

I think the blower control module is dead too but I don't want to toss good money at the pob w/o testing it more - I don't have much to spare .

On this car tho it is not just a resistor pack...it's some kind of electronic crud mounted on big heat-sink. Hard to believe but, at 24 y/o, I long for the old days.

 

You should be able to diagnose the problem with a test light or volt meter. The blower motor resistors are usually the first part to go. W/o looking at the shop manual, you can jump the terminals on the resistor or bypass it to see if it's defective on most cars. You should have varying voltage output on the module side if you test it with a volt meter and adjust the blower speeds.

 

I had bad connection once at the control unit that sits on the firewall and it did the same thing.
Before that I had a burnt resistor on the board of the electronic climate control unit in the dash. It was so discolored I couldn't read the value, so I went with the larger possible value resistor at Radio Shack, 5 pcs. for $.79, worked like a charm.

 

Electronic Air uses a Blower Module that receives low voltage signals from the Dash Controls and then amps them up to run the Blower. Module Power is from a fusible link and so that's red at the Module and you should check it first for Battery Voltage. Blower Input from the Dash is Brown and at "1", it should have about 2.5 volts; at "10" about 6 volts. Output is whatever is hot at the Blower Motor - Purple for the last 16 or 17 Years for most GM's, but yours may be Black/Red. Anyway, at "1". the output should have about 4 volts and at "10", 12 volts. Auto 60 should have battery voltage and the blower should be running at full trot. If it has the input but no out, buy a new Module. If nothing is coming in, you'll need to ohm out the Brown back to the Dash and if good, replace the Dash Controls. Do check Module ground. It's spliced into the Blower motor ground and terminates on the frame, kinda below the whole shebang. Also check your blower connector - especially if it has an output and the blower isn't spinning. Contacts are crimped to the wires and the wiring is marginal for the load. A voltage drop at the connector can melt the leads, usually where they enter the connector. If it's discolored, take apart the weatherpak and solder the terminals to the wires.

 

I double checked the color and I do have blk/red at the blower and module. It reads 0v no matter the fan setting. However, the brown wire reads 7v no matter the fan setting.

Does the blower control module from a 90 work in an 86? If it does then I can just swap it over to test.

Any ideas?

Thanks!

 

Input looks right - just make sure the Module has power and ground. Don't think the '86 and '90 are interchangeable. The '86 Module also supplies compressor ground whereas the '90 operates the compressor via the ECM. You can go to www.acdelco.com and look up the part#, then use their cross-reference to see what Years interchange. All the modules seem to be about 100 Bucks new and they're used across the line, so don't let someone charge you a Vette Tax when you can buy a Buick.

 

I had similar symptoms as you. I drove myself crazy trying to track down the bad part. SunCR's suggestion on the connectors to the blower motor were right on the money. I ended up swapping out the blower motor rather than soildering anything since my soildering is no better than my spelling!

 

UPDATE:

I checked on the ACDelco site and the P/N for the 90 and 86 are different but the connectors and pinouts are the same and the FSM for both cars indicates the same signals/voltages for normal operation. Given this, I tried swapping the 86 module into the 90 and it works perfectly - full blower control. I swapped the 90's into the 86 and nada.

To me, this sounds like it is not the blower control gizmo causing my problems. I rechecked the voltages and the big red wire (from a fusible link) is at 12v+. The brown wire (signal from programmer/head) is at 11v - this is a bit high I think. I did this check with the connectors unplugged - does that make a difference?

Anymore ideas?

 

Not having a '90 schematic at my fingertips, I can't say for sure what the differences are - but I'm pretty sure the '90 drives a compressor relay through the ECM and the '89 and below through the Blower Module. Hence, you've got an ignition signal from the Dash Controls to the Module on the '86 and when the Module sees that, it grounds the Compressor. On the '90, compressor signal is from the Programmer to the ECM which then drives a Relay. On the '86, compressor circuit is usually a green/yellow wire from the Dash and the compressor ground is green.

Disconnected, the Dash/Blower signal might rise, but it should be close to the connected "10" input or somewhere around 6 to 7 volts. Check Voltages at "1" too and if that's somewhere around 2.5 volts, Dash Controls are probably ok.

Now sounds like you might have a bad ground - shared with the Blower Motor. I'd check that connector again - trace ground from the Blower Motor up to the splice (you'll have to unwrap the harness). If the Module isn't grounded, it ain't gonna work.

 

You are correct. The 90 does not use the blower module for anything other than the blower - no compressor goodies. However, all the connectors are the same and the pins are all available - just an interesting side observation that the 86 module will work with a 90 vehicle.

That's the thing... At "2" on the head unit, the brown wire (signal) is at 11v (unplugged) and 7.1v (plugged in). The same when set on "10".

I tried to get to the splice but I cant get the harness apart without removing most of the AC stuff - everything is wrapped together and I cant get the wires out to inspect anything. I'll keep trying tho. I did measure the resistance to ground from both the module and the fan and got about 0.5 ohms. Unfortunatly, this doesn't mean much - I have been fooled before.

 

I just tried running a new ground from the blower (since it is spliced to the module ground) to an engine accessory (again 0.5ohms) with no success.

 

Your inputs from the Assembly are too high and with little to no spread between the numbers, sounds like you need a new one; however, I don't understand how there's no output - even with 7 volts at 1 it should have the blower cranking (if the Module and wiring are good). Check the 5 amp fuse on the Firewall. That's spliced into the Blower output and protects the circuit carrying actual blower voltage back to the Control Panel. When it opens, all you get is high blower and if it has, that will explain your inputs from the dash.

Unfortunately, the high voltages may have fried the Module, but if it worked as advertised on your '90, it sounds like it's ok. Verify voltages to the Control Panel by checking the Gages (ignition) and Courtesy Clock (Memory) fuses. I'd then recheck by jumpering red to black/red to make sure the blower motor runs on the battery feed to the module -I'd also read from red to black to re-verify the ground - ditto brown to black. Not much else I know to do to troubleshoot it. Some have had the double failure - control panel and module.

 

The 5amp fuse under the hood is ok.

I just re-checked the voltage at the red wire (main power in) and it is reading 5-6v to the engine block and to the black wire on the module. WTH! It was 12 earlier. I guess I need to trace that back to the fusible link (book says it is near the starter somewhere) and see what is up.

I would also not be surprised if the control head was fubar either. The "UP" fan button just decided to stop working today, too. The "DOWN" works fine tho. Maybe it just need have the grounds cleaned or something.

This car is really getting on my nerves...

Thanks for the help!

Dale

 

Measure again with it disconnected - first red to ground and then red to black. If you have Battery voltage red to ground, the wiring is ok. If it drops red to black, the ground side is bad. If it drops - while connected - red to black, it's the Module (but there's probably some resistance built into it).

 

PROBLEM SOLVED

Today, I ran a 12v line to the module to bypass the OE one and the blower works as it should so I figured the problem is in the main power line to the blower module - it may be getting the voltage occasionally but not delivering the power. I got under the car and the fusable link wire measures 15MOhm from blower module to starter - not good I think. I pulled it apart and it appears to have been a bad joint that finally let loose.

After a trip to AutoZone to get a new link, all is well. The blower now works at all speeds despite the previous voltage readings from the head.

This is the second time I have encountered a connection that showed the proper voltage during diagnosis but was still bad. Both with A/C too. Maybe I am destined to not have A/C

Thanks for the help everybody!!!!

Dale

 

Neato! There have been a couple of posts about fusible links losing their insulation and fraying wires - generally the ones behind the battery where they're a little more visible.

 

I'm glad you got your fixed. I have the problem of everything working manually, but not automatically. I wonder if there's some fusable link messed up on my system somewhere. Here's a post I made recently covering the details.....

I have a 1991 A/C with the automatic A/C. I absolutely hate this thing. I prefer a manual valve....fewer headaches. This is my 3rd C4 with these things. With that said...My A/C has a new control head, program module, compressor & clutch, lines, accumulator, self-adjusting orifice tube, evaporator core, condensor, freon, & a few sensors.

Here's the latest problem that has occured..... The AUTO settings reset to 75 degrees everytime I turn the key off, & the blower fan won't come on in AUTO mode. If I move the blower FAN controls higher or lower, the blower will come on, but if I press the AUTO FAN button located between the UP & DOWN FAN control buttons, or the main AUTO button, the fan just dies. I'm not sure if it's a relay, switch, the resistor, or what that's causing the AUTO & AUTO FAN problems.

Any ideas before I start testing piles of stuff on this thing?

THANKS!!!!!!!

P.S. I'm beginning to lead toward the Temperature Door Motor (or something controlling it) going bad, also. I used to hear it come on whenever I put the key in the car, but I haven't heard it lately. I know my unit should read a code 01 or 02 if it does.

 

I'd guess an intermittent in the power supply or ground - memory side since it happens once you turn off the key. Once memory is erased, nothing works for a few seconds (to a couple of minutes) while the Programmer learns the position of the temp door. 75 is usually the default, so if you disconnect and reconnect the battery and that temp shows up, you should probably look at the connector and make sure it's got a good ground because something is momentarily coming undone somewhere.