Electrical Gremlin: A/C and Radiator Fan

[hEaT]

I have an odd electrical issue on my 85. When the battery is hooked up, the main cooling fan turns on. When the ignition is turned on, the A/C pusher fan turns on. The only way I can stop the radiator fan is if I disconnect the battery. I unhooked the fan switch (plug facing firewall below the lower intake) and the fan still turns on.

Using the 87 EVTM, as soon as the car is powered, the #1 A/C Temp Switch relay trips. This is the relay when looking at the car from the front, it is all the way to the left and at the back of the fuse box. If I pull the relay, none of the fans turn on and the car behaves normal (no way to turn the fan on at all though).

Checking voltage at the pins with the car powered (looking at the car from the front again), the pin at the right and front are both getting 12v. The pin at the left is grounded and the pin at the rear is grounded, but either a bad ground or through a resistor since it shows a difference of 11.9v, not 12.2v like the rest.

If I leave the battery hooked up, the fan will run until the battery dies. I swapped relays with the fuel pump and the problem still exists. The car runs and drives like normal besides this fan issue.

I'm trying to see other things that would cause the fans the turn on besides the fan switch. I'm not great at reading electrical diagrams, although I am learning.

I'm guessing this could be a possible short as well somewhere in line between the fan switch and relay? I didn't have a chance to check continuity between the pins on the switch, but I can do that to see if there is a short.

Any ideas? I cleaned the ECU ground and the ground on the lower intake. I checked ground on various spots on the motor and I see .2ohms all around.

[CV12Steve]

In the '85 the cooling fan circuit is always hot, and the fan can run at any time. This was changed in later cars to a key on hot circuit.
Sounds like shorts if both fans are running.

[Ed Lijewski]

The actual relays for those fans could be bad. I assume on the 85XR they are in the same location as for later years, to the left of the radiator inside the engine compartment, just in back of the left hand side headlight housing.

YMMV

[hEaT]

Thanks Ed, I'll check that out.

[DPDISXR4Ti]

Yep, it's almost asuredly those relays attached to the forward portion of the inner fender (driver side). They're notorious for going away since they're not sealed from the elements. I'd suggest replacing them with a weather-tight relay - junkyard GM vehicles can be easy donors of the harness and relay. Alternatively, circa '87 - '93 Mustangs use the same relay for the fuel pump - it's located under the driver seat.

[CV12Steve]

Alternatively, circa '87 - '93 Mustangs use the same relay for the fuel pump - it's located under the driver seat.

You mean the weather-tight type?

[John R. Rowlands]

hEaT,

The switch that controls the heater fan/AC pusher fan, is located on the dash. Pushing the switch in should turn off pull it out to turn the AC pusher fan on. Try that and let me know what happens.

John

[DPDISXR4Ti]

Alternatively, circa '87 - '93 Mustangs use the same relay for the fuel pump - it's located under the driver seat.

You mean the weather-tight type?

I knew when I typed that I wasn't clear enough! The Mustang fuel pump relay is identical to the original fan relays used on the XR. No re-wiring needed - just remove good relay from under the Mustang driver seat and plug it into the XR's harness in place of either of the originals. Clearly this is the easier option, but you're still left with a NON weather-tight connection that is exposed to the elements.

The weather-tight relay from a GM - Cadillac's are ideal and super easy to locate/remove - would require clipping off the original quick connector(s) on the XR, and replacing both the relay and quick-connector pig-tail, as donated from the Cadillac.

One of these days I'll have to clearly document this swap. Feel free to give me one of these at any time...

[hEaT]

hEaT,

The switch that controls the heater fan/AC pusher fan, is located on the dash. Pushing the switch in should turn off pull it out to turn the AC pusher fan on. Try that and let me know what happens.

John

Both fans are on with ignition on and it doesn't make a difference if the A/C light is on or off. I used to control the radiator fan this way turning it on and off. Now it doesn't make a difference what position the switch is in.

Yep, it's almost asuredly those relays attached to the forward portion of the inner fender (driver side). They're notorious for going away since they're not sealed from the elements.

I looked and I didn't see any relays or wires except for the signal and level sensor on the bug juice. Where are they exactly? I pulled the grill and looked around the headlight area and didn't see anything. I also pulled the washer reservoir and there is nothing in that area. I looked on Ray's 85 with the same results. I have wires running along the frame rail with a connector that goes to the radiator fan. I don't see any relays in that area either.

[DPDISXR4Ti]

I looked and I didn't see any relays or wires except for the signal and level sensor on the bug juice. Where are they exactly?

As you stand in front of the driver side headlight (with the hood open), stick your head in there and look behind and to the right of the headlight on the inner fender. They're somewhat hidden by the pinch-weld overhang flange where the inner/outer fenders and radiator support are all spot-welded together.

[hEaT]

Here is a shot behind the driver's side headlight. The washer bottle is removed for clarity. Is this where I should be looking?



The top plug here operates the radiator fan. I can see the wires do a straight shot along the fender under the coil and towards the firewall. The two wires you see going towards the fender are for the signal and for the fluid level sensor.

[DPDISXR4Ti]

Here is a shot behind the driver's side headlight. The washer bottle is removed for clarity. Is this where I should be looking?

Yep, exactly. I thought all XR's had them located there, but perhaps the early cars didn't. Either that, or they've been removed. I see what could be the witness marks and hole from one, but that might be from your washer bottle bracket - yes, no, maybe???

Have you got a '85 Electrical Trouble-shooting Manual? In my '88 manual, it correctly indicates on page 93 that the A/C Condenser Fan Relay and Engine Cooling Fan Relay are located "Near Windshield washer bottle".

[hEaT]

I see what could be the witness marks and hole from one, but that might be from your washer bottle bracket - yes, no, maybe???

Yup, that's from the bracket for my washer bottle.

Have you got a '85 Electrical Trouble-shooting Manual? In my '88 manual, it correctly indicates on page 93 that the A/C Condenser Fan Relay and Engine Cooling Fan Relay are located "Near Windshield washer bottle".

Just the 87 manual unfortunately which also says the same thing for both the A/C Condenser Cooling Fan Relay and Engine Cooling Fan Relay.

The search continues

Thanks for your help so far.

[Ray]

Joe,

Why dont we just cut the wiring to the fans and isolate them via a relay that we could locate in a place that we can find? it wouldn't be hard to do and relays are cheap. I have a whole crapload of ford relays from my parts focus.

Brad,

We looked on my 85 and also couldn't find these relays for the fans in that spot. I'll take another look and trace the fan wiring back if i get a chance this morning.

[DPDISXR4Ti]

Brad,
We looked on my 85 and also couldn't find these relays for the fans in that spot. I'll take another look and trace the fan wiring back if i get a chance this morning.

Yea, I noticed Joe's comment about that, and also noticed that you both have 85's. Sure sounds like they were located elsewhere on the early cars before being moved to a less hostile location later on. I think they would have been better off changing the relay type than the location, but what do I know?