I am trying to get my A/C working currently the blower motor will not turn on. This is what I know so far, the switch inside works, with it off the purple(ppl) and black (blk) wires have no juice, with it on anything BUT high the ppl wire has 12 volts. With it on high the blk wire has 12 volts and the ppl wire is dead.

I know the blower motor works, I removed the motor and hooked just the purple wire up and ran the blk connection to ground and the motor turns on when the switch is on anything but high. I'm thinking this means that the ground isn't being completed since I know the motor works and it is getting power.

The question: Isn't the blk wire supposed to provide the ground? According to the electrical diagram the blk wire is spliced into a ground connection and I'm guessing the orange side is power. Where does the ground come from if it isn't the blk wire to the blower? I have tested the blk wire in all switch positions and it NEVER gets a ground reading via my OHM meter.

I read in another thread on here (somewhere) that the ground is done through one of the bolts that goes into the firewall but no bolts touch any metal on the blower and then go into the firewall.

Is there a way I can jump the ground connection to see if that is indeed the problem? Where do I hook it up to, I tried the metal mount of the blower motor but that didn't work.

Or can someone check their black wire and see if it ever reads a connection to ground? Thanks

The diagram for your viewing pleasure..

 

From your description, you have a bad ground connection. However the ground connection is not at the blower motor. See the note highlighted in yellow on the wiring diagram you posted "For Ground Detail see Air Conditioning (Compressor Control)". I have an 82 and the ground connection for the blower motor and AC compressor is on the engine, near the AC compressor. On the next page, or near the AC compressor control page you should have a table, "Component Locations" . This list should tell you where G112 or G113 is located.

I did disconnect the black wire at the blower motor in my car and got a 0 ohm reading to two different ground points in the engine compartment.

You can make a jumper with #12 wire (you can get a few feet at any hardware store for a few cents a foot. You will probably need 4-5 feet.) and two agalligator clips. You can remove the black wire at the blower motor. Hook one end of the jumper to the spade lug on the blower motor that the black wire was removed from. You will need to hook the other end of the jumper to the ground connection to the body at the battery. Try the blower motor in one of the low speeds. Hi speed will not work in this setup as the coil for the high speed relay will not see a ground.

Hope this helps you fix your problem.

Dave

 

Thanks for the reply Dave. I see what you are saying there, but wouldn't the ground need to ride on the black wire that goes to the relay, which then splits off to the black wire to the blower? I mean, the motor simply will not run if there isn't a ground present to complete the ciruit. With the blower motor out, looking at where the black wire connects (spade as you called it) is basically just a screw through the metal front panel the motor attaches to. There are no connections on the other side so this must be the ground point.

I already tried what you suggested and by grounding the spade connector the fan works fine in every position except high (which is expected). I will trace back the ground like you said but I am still confused as to how there isn't a ground reading on the black wire going to either the relay or blower motor itself at any time.

 

The ground point you describe is for the blower motor coil only. However the metal cover over the blower motor is not grounded to the car by the A/C duct housing. There is a seal between the housing and the firewall that acts as an electrical insulator so no ground connection will be created. You are correct in that the ground for the blower motor and the relay is carried along the black wire. However neither the blower motor nor the relay are grounded. So you have to follow the dashed black wire in the wiring diagram to find where it is grounded, or connect to the engine or car frame.

Current flow for the blower motor is from the battery, through the HTR A/C fuse, down the Brown wire to the A/C control head, through the function selctor switch to the speed switch, via teh Brown/White wire, through the speed sleector switch for LO, M1 and M2 to the blower motor resistor, down the Purple wire, through the blower motor coil, through the Black wire to terminal E of the Blower High Speed Relay, down the dashed black wire to G112 or G113 to Ground and back to the other side of the battery.

Well there is supposted to be a ground reading, as you expect. However, you appear to be the victim of an OPEN CIRCUIT somewhere on the black wire from the Blower High Speed Relay terminal E to the ground point at G112 or G113. So no current can flow and the blower motor will not work. Also, the Blower High Speed Realy coil will not see a ground and will not energize. Since it will not energize, the relay contact between terminals A and D will not close, porviding a current flow for the high speed operation of the Blower Motor.

The Open Circuit can be created by a broken wire, somewhere along the length of the wire, the wire is broken at a terminal connection, such as at the Blower High Speed Realy terminal E, or the Ground connection at G112 or G113 is loose or the bolt is missing and the black wire terminal lug is no longer in contact with the engine or car frame.

Dave

 

It's hard for me to tell but it seems like the ground is somewhere in the cabin? I traced the black wire and it looks like it runs through the firewall directly in the center of the car. Can anyone confirm this? I don't want to take my console/radio/a/c controls out if I don't have to. I'm guessing the ground connection is somewhere behind there.

 

I have not taken apart my AC controls or my console. however, I would say that the ground you are looking for is in the engine bay or on the engine, not in the cabin of the car. Unless some one has rewired your car.

Does your service manual have complete wiring diagrams in section 8C? These will not be in color, just black and white. In my 82 service manual they cover 11 pages, covering the body wiring, accessoriy wiring, engine bay wiring and EMC wiring. The last sheet in my book shows the Blower motor, the Blower Resistor and the Blower High Speed realy. From this page there are three wire associated with the AC Heater system that go to the engine: RED to the battery for high current to the blower motor when in high, circuit #2; BLACK, the ground you are trying to trace, circuit #150; and a LIGHT BLUE wire from the Cycling Pressure Switch, circuit #67. (The Cycling Pressure Switch is located just in front of the Blower High Speed Relay. The LIGHT BLUE and the Black wires join the engine wiring harness along the fire wall just behind the block, making it difficult to trace .

In my car on the left side of the block these two wires join a connector. On the other side of the connector a DARK GREEN wire, circuit #67 and two BLACK wires, circuit #150 leave. One BLACK wire and the DARK GREEN wire are in a harness that goes to the AC compressor. The other BLACK wire goes to the ground point you are looking for. Sorry but I haven't pulled the Cross Fire Air Filter off to look for this ground point. Your car should have similar wiring. Your problem is most likley at the junction of the BLACK wire to the AC compressor & the BLACK wire that goes to the ground point, or at the ground point.

Spend a little time trying to trace the circuit through the wiring diagrams in Section 8C. Then take another crack at finding this ground point in your engine compartment. It might be easier to trace the circuit by starting at the AC compressor and working back along the path of the DARK GREEN adn BLACK wires to the ground point and to the Blower motor, instead of starting at the Blower motor.

Hang in there, I think you are close and will figure this out soon

Dave

 

I was checking out those black and white diagrams last night, when I get home I will post a picture but they sound pretty much the same as what you have described.

A problem here is when I had a LS1 engine installed in the car the A/C hasn't turned on since. They cut the dark green and black wires you are talking about that goto the compressor. They cut these wires just before they go into the firewall (right near where the big black wire from the blower connection goes into the firewall dead center low behind the engine). The only way I could even get to the dark green and black wires was to remove the entire heater box/blower assembly. That is NOT something I want to do again. Now I am thinking the easiest method will be to create a new ground rather than diagnose the existing ground that I can't get to/find. It would just be a matter of finding the correct spot to hook this new ground into and what gauge wire to use. I will update this when I get home tonight with what I find.

 

Ok so it sounds as if some of the wiring was modified when the LS1 engine was put in.

Making a new ground for the Black Ground wore from the Blower motor should not be that hard. I went out tonight and traced the wiring as far as I could, before it disappeared between the block and the fire wall, under both heater hoses and the dizzy.

First choice for a gorund should be the ground point on the firewall just above the dizzy. I have a braded copper wire and an insulated Black wire there. The braded wire goes to ground the block. I think this is where the Balck wire from the AC compressor and the Blower motor was grounded. So either side should be ok. You can also run the new ground in the wire harness from the blower motor and resistor area.

Second choice in my car, and maybe first in yours is if you have an under hood light. In my car that ground point is jsut behind the RH hinge and just in front of the blower motor. This point has a black wire from the under hood light and a braded copper wire from the hood insulation.

Third choice would be the ground point on the RH fender next to the radiator coolant recovery bottle and just behind the battery.

You may not realize it but you already have the wire size, but the metric version. Take a look at the diagram you posted up top. Look at the Purple wire from the Blower Resistor to the Blower Motor......3 PPL. Same for the Black Ground wire.....3 Black. "3" is the metric wire size. Now take a look in your service manual for Chapter 10 in the BODY section. There is a conversiontable on the first page of the chapter for Metric wire size in mm**2 to English AWG size. Also page through chaper 10. You should find a diagram showing the wiring harness routing for the interior of the car. The one for the console area shows a ground point at the rear end.

Ok here are some photos of the ground points....The first is on the firewall at the distributor. The second is at the Right Hand Hinge and the third is at the battery.

Hopefully everything will work correctly after you connect up a new grond point to the Blower Motor Black Ground wire. Let me know how it works out for you.

Dave