mahnu

I am trying to fix a problem with the blower motor function and could use some help. I have gone through some of the suggestions on this forum and I remain stuck.

Symptoms – The blower fan works intermittently.

- When it works, all speeds and Def functions work as they should.

- When it does not, all speeds do not activate the motor and Def setting does nothing. This is with the AC button in both on and off positions.



At first, I suspected the relay, which led me to trace the circuit diagram. The relay works, as I have bench-tested it and swapped it with the horn relay.

Jumping pins 30 and 87 enable the blower and all the speed settings for the fan speed work as they should.

This led me to look at pins 85 and 86, which enable (close) the 30-87 circuit.

Pin 85 goes to the ground, which leaves 86 as the problem. 86 is not powering up. According to the circuit, it is fed from a Control Unit and an AC control switch. I am testing this with a multimeter. The AC Control unit is part of the blower control head. I have removed this and cleaned the contacts, which did not resolve the problem. I also disconnected and cleaned the contacts to the AC toggle switch. The AC Control unit is labeled “rebuilt,” and I may open it to re-solder the connections as a next step.



I also removed and cleaned the contacts of the “IV” relay, which is labeled “X Relay” on the wiring diagram. According to the fuse layout, it is an ignition relay. I would think that the car would fail to start if this relay were bad.

I do not know where the “Control Unit”, per the wiring diagram, device is located.





Any help is appreciated.

Eplebnista

Model Year would really help.

gazfish

The control unit is mounted on the side of the transmission tunnel and connects to the blender flap. If defrost isn't working when it all fails then it's more likely to be the motor or the connection to it, as defrost bypasses all the fancy controls. Have you checked the ground connection of the blower motor?

Alan

Since neither the normal blower switch or DEF modes reliably run the blower there are only 2 obvious commonalities - The HVAC head unit and Fuse #17 that feeds the blower for either mode. Test, clean & reseat Fuse #8 as this feeds the head unit and Fuse #17 (the higher power fuse). You can test the ATC fuses in circuit - the dimples in the fuse face allow you to access the terminals - the top terminal is the input - the bottom is the output ('85 and later cars only), Fuse #8 is fed by a direct ignition (15) supply, fuse #17 is a direct battery (30) supply.

Pin 10 on the HVAC head is the power in (also on CE pin G13). The HVAC DEF output that controls the DEF relay is on CE pin G15.

The control unit has nothing to do with the blower, the "Ignition" X-Relay (Relay # IV) is for non engine critical circuits also controlled by ignition so the car will indeed run without it. For this model year it is not involved in the HVAC.

Alan

mahnu

Thank you all fir forthe help here.
I was able to locate the control unit and found no power to it. This was helpful in better understanding the circuit. From this, I traced the wires back to a connector that was faulty. Apparently, this was the source of the problem.