high speed fan not coming on?

94GTMustang5.0 · Nov 8, 2010

I have a 94 GT. Brand new OEM radiator, 70/30 water-coolant ratio.

Long story short, i was using the heater in my car this morning (it was 43 degrees this morning in Clearwater, FL where i live.) and I noticed the temp gauge was climbing, when it hit the "L" in Normal, I pulled over and shut the car off. I let it cool for 20 mins and restarted it with the heater on.

i noticed the fan was not coming on, even at the L in normal
with the heater off, only the low-speed fan is coming on to cool the car.

What gives? Do I need a new fan? Fan motor? or maybe just a fuse or wiring problems?

SorsCode · Nov 8, 2010

Could be a few things. I've see thw wiring break betweent he Fan and the CCRM and cause this kind of behavoir. Look at your CCRM (module thats infront of the fan on a bracket holding overflow tank, if car is stock) is it Blue labled or Brown? The V8 cars came with the Blue labeled ones which gives you both high and low speed fan, if its Brown then it will be Low Speed only (if it came out of a V6 Mustang, not always true but possible). Also check the pins on the fan motor themselves for the wiring. If they run alot they seem to go bad.
Hope this helps to get you started troubleshooting the issue.

Last5.0 · Nov 8, 2010

Could be a bad relay in the CCRM, could be a fuse in the power distribution block, could be a bad fan motor.

Does the high speed fan come on when the a/c is turned on?

Do you have the "Ford Recall Fix" circuit breaker between the fan plug harness and the fan motor? If so, remove it and see if the high speed fan works. This is an inline plug block that has self resetting circuit breakers that may have gone bad.

94GTMustang5.0 · Nov 15, 2010

When i turn the A/C on max, the high speed fan does not come on.

with the heat on max, the fan does not come on. No matter what i do, I cant get the high speed fan to come on. Only low speed comes on. I checked the relay for the fan in the power dist. box, and it was good.

What else can i check? how can i diagnose a bad fan motor/bad relay in CCRM?

The fan spins freely and i cant feel any resistance, low speed fan works well.

Last5.0 · Nov 15, 2010

High speed fan will not come on when you turn heat on.

Do you have the "in-line" circuit breaker at the fan plug? It's a black plastic box about the size of a pack of smokes with 2 silver colored self resetting breakers epoxied into it (I attached a pic). If you do, remove it and plug the fan in directly and see if you get high speed when a/c is turned on.

If not, you need to...

1. test fan to see if it works
2. test wiring going to fan to see if there is voltage

HISSIN50 · Nov 15, 2010

Have you tried grounding CCRM Pin 17 to see if high speed will engage? CCRM Pin 17 is the relay trigger from the EEC.

General diagnostics:

If high speed doesn’t come on at ~228F or with the A/C turned on, but CCRM Pin 17 shows continuity to ground: With the key-on, check CCRM pins 6 and 7 for 12 volts when the high speed fan should be on. Check Pins 3 and 4 for constant 12 volts. Check Pin 13 for key-on 12 volts.

94GTMustang5.0 · Nov 16, 2010

I dont have the circuit breaker thing attached, the plug just goes straight into the fan.

I noticed something odd today, as I was driving home the temp gauge was sitting a little above the "R" in normal. the oil pressure gauge will usually sit right on the A or L in NORMAL. When i turned on the headlights, the temp and oil pressure gauge went up a little, when i hit the brakes with the headlights on they went up a little more, then I turned the interior fan speed to max, and the oil pressure gauge was almost maxed out, and the lights dimmed and the temp gauge jumped straight to the L in normal. I could turn them off and they would return to their previous position before i turned on all the lights, etc.

What could cause this? maybe the fan motor is shorting out?

HISSIN50 · Nov 16, 2010

More likely a bad ground.

94GTMustang5.0 · Nov 17, 2010

a bad ground where? I hate to ask so many questions, but im not too good with wiring or a voltmeter. Could this bad ground cause the fan to work intermittently?

HISSIN50 · Nov 17, 2010

Sorry, I should have quoted your message. The bad ground comment was only intended for post 7 (the gauge issue).

5.0_GT_kid · Nov 18, 2010

So apparently they got the high speed fan to come on now, but the low speed isn't. Very odd.

Oh, and my car doesn't have 270k miles on it. 240-250k would be a more reasonable estimate.

HISSIN50 · Nov 18, 2010

I'm confused about who is posting what (I assume this is all the same car with two people referring to it as their own).

What was done to create the new changes?

5.0_GT_kid · Nov 18, 2010

The OP is my younger brother. The car is mine. I'm letting him drive it for the time being, so he's taking care of the maintenance issues.

I'll have him post up later and detail what he did. I wasn't at home when he was working on.

94GTMustang5.0 · Nov 19, 2010

I changed nothing and now the high speed works, low doesnt.

Before, only the low speed would come on and the temp gauge would hit the "L" in normal, and eventually the fan on low would bring temps back down to the middle of the gauge.

Now the high speed fan wont even turn on until the "L" on the gauge, and it brings the car back down to temp.

HISSIN50 · Nov 19, 2010

You're going to want to have a means of seeing the actual temp so you can try to figure out what's going on.

5.0_GT_kid · Nov 19, 2010

Another thing to mention is that the upper radiator hose does not get warm or feel like it has any pressure inside of it.

toyman · Nov 20, 2010

5.0_GT_kid said:
Another thing to mention is that the upper radiator hose does not get warm or feel like it has any pressure inside of it.

That would seemingly indicate the T-stat isn't opening, the rad is plugged somewhere or the water pump has died. My first guess is the pump.

94GTMustang5.0 · Nov 22, 2010

Can water pumps fail without water pouring from the weep hole?

The water pump doesnt leak at all and hasnt ever given me any problems, and it visually appears to be the original pump.

I have noticed that as the car runs, there is a low-pitched intermittent hum that is coming from the very front of the engine, but it comes and goes and its barely audible.

When-or if-the fan comes on, temps will stay right in the normal range. it seems to be that the fan just doesnt want to come on at the right times.

Last5.0 · Nov 22, 2010

Do you have any diagnostic codes from the EEC? How old is the ECT sensor?

Seeing that you just installed a new radiator and refilled the cooling system, did you purge the air out?

What about the tstat? Did you replace it and is it installed in the correct direction?

5.0_GT_kid · Nov 23, 2010

We pulled the fan out of the car and tested it with the jumper wires. High and low speed both work. It also appears the thermostat is bad.

Hissin, can you provide some more info on testing the CCRM? I'm looking at this schematic but don't see a pin 13.

http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-CCRM-AC-Diagram-2.gif

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