I have a 1989 240 DL Wagon, the fan blower for the heater started blowing by it's self. I removed the fuse for the blower, it kept blowing. I turned the blower motor to the on position and the blower stopped. Now the turn signals don't work. I'm baffled by this, if someone has an idea I'd really like to hear.

Thanks
Barry

 

The car sounds possessed! I would start by inspecting and cleaning all of the fuses.

 

Check your ground circuits. Sounds like power to flowing from another circuit into the ground wire for the blower. That is why it stops when you turn it on, you have power on both sides of the motor. That fuse proabably also feeds the turn signals.

Russ

 

Bubba, was that the problem?

I'm having similar problems with my 740, with the ignition on, the blower motor stays on when it's set to off.

 

Sorry Bubba, I meant Barry.

Anybody still around for this thread?

 

if the AC is enabled, it forces the blower to be on at least low (1).

what year 740 is this? I only have wiring diagrams for 91/92 7's

 

Hi Pierce,

Derp... it's an '89 GL.

Thanks!

 

...At least when the ignition is off, it's OFF, so that's something...

 

make sure your AC isn't on. if this is like a 1991 (oldest print I have), with the 3 rotary ***** (fan, air control, and temp) and 2 buttons underneath, the right button is IN to disable AC and OUT to enable it. AC is also forced when the middle **** is at 12 o'clock aka 'defroster'.

the fan speeds are controlled by a resistor module thats on the outside of the fan housing, under the glovebox, behind the kick panel. I'd remove the kick panel, the knee bolster and the glove box for the best access. on my 1991 prints, this resistor has 3 connectors, one of them has 4 wires, 1,2,3,4 for speeds 4-3-2-1 respectively. high speed (5) goes to a red-white wire to pin 2 on another connector, which is direct to the motor.

this resistor module is known to fry, and do funky stuff.


hmmm. this print has a notation "AC will not operate unless fan is running", which is the opposite of my experience but I've only got a 92 740 and a 87 240, and I'm pretty sure on either of those, engaging the AC forces the fan to be on low speed.


anyways, the power to the fan goes like this... ignition switch pin "X" (on in I and II) goes to fuse 16 via a black wire. another black wire goes from fuse 16 through a connector A pin 1 to another black wire to the heater fan switch pin 1. heater fan switch pin 2 is a red-white wire to the fan resistor, heater fan switch pins 4-5-3-1 also go to the fan resistors various inputs and resistor pin 2-the-other is a red-white wire that goes through a connector "N" right at the fan which goes the fan itself. confused yet?


OH. this whole mess is grounded at the right A post, near/below the ECU. this is to the right of the US-passenger-side footwell (remove the plastic side panel after removing the kick panel. if that ground is bad, all bets are off. the white-black ground wire ALSO goes to the connector "N" thats right at the fan itself.

 

Thanks Pierce,

It's a dual-slide control, top is AC, vent, mix, feet, def, etc., bottom is temperature. Fan **** (0,1,2,3,4) to the left of the sliders.

 

ok, I've got nothing showing one of those or how its wired.

its probably similar.

 

It stopped doing it.

Ah, the self-healing brick!

 

I had the same thing happen in my 91 Volvo 240 wagon. I found that the wires to the tailgate that run through the hinge on the top broke and then shorted to the car. when this happened my heater fan would run when I hit the brakes as the center brake light runs into the tailgate and was obviously backfeeding through ground causing the fan to run...... took a while to figure out but found it. one weird gremlin for sure