Fan not coming on...any help...

98stangv8

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Ok...just had the lower intake replaced..and now the fan isn't coming on, and the car is obviously overheating...where do I start?

Checked the main fuse under the hood in the box for the fan and thermostat...no problems there..

Any other fuses? Or do I just have to replace the thermostat?

Thanks!
 
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squeak93

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Can you override the fan to make sure it works? ie... hard wire quickly just to test its not the issue. There should be a fan relay as well. Check that.
 

COramprat

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Do you know where the fan relay is located? Any help would be appreciated...as I couldn't find it right away..
The fan relay is part of the CCRM...it's a black box located under the splash guard of the passenger side fenderwell.

Before pulling that though I think you have something related to the intake install. Make sure the electrical connector to the fan is secure. Mine crapped out after removing it a few times and the prongs lost a solder joint. I could wiggle the connector and the fan would run.
 

98stangv8

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The fan relay is part of the CCRM...it's a black box located under the splash guard of the passenger side fenderwell.

Before pulling that though I think you have something related to the intake install. Make sure the electrical connector to the fan is secure. Mine crapped out after removing it a few times and the prongs lost a solder joint. I could wiggle the connector and the fan would run.

that relay was the first thing I checked...along with thermostat one..good to go on those..

wiring harness is good...just had that replaced not too long ago as well..

could it be the thermostat?
 

squeak93

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The thermastat is a mechanical part. If its not opening right then the coolant won't get to the temp sensor that I imagine triggers the puter to turn the fan on. Or the sensor could be bad.

My bad on the relay location. Was using google and that's what it said, its free for a reason. :D
 

GT Tommy

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Cooling fan not coming on!

Here are two electrical cooling fan circuits. The top diagram is for a 2003 GT 4.6 Mustang. The lower diagram is for a 1994-1995 GT 4.6 Mustang. Check out the different fuses used for the fan circuits.
Hope this helps. Good luck, Tommy.

2003GTMustang46fancircuitdiagramwit.gif


1994-1995GTMustangConstantControlRe.gif
 

markandjay

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You said you just had the lower put on...I would check the wires going to the fan therm switch in the water jacket it is a screw in type right by the thermo housing it is a normally open circuit jump the 2 wires going into this switch at the connector and the fan should come on. I cannot remember if the key needs to be on or not...sorry. if fan comes on it is a fan therm switch prob.
 

98stangv8

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Ok...really crazy...I went to get it looked at...and it was working...so I thought it was just a temp glitch..

Then, after driving for about 40 minutes, I was sitting idle in a parking lot..engine on...fan working fine...I turn on the A/C..and after about 5 minutes..rpms climb for about 15 seconds to about 2000, A/C starts blowing warm...and the fan stops working..engine starts overheating...


Let the car sit..and the fan works fine...a/c works fine????


WTF?
 

COramprat

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The high speed relay in the CCRM isn't working.

The low speed fan runs at idle or normal operating temps. Once the AC is turned on the high speed takes over. If it is shutting off when the AC is on I'm betting the high speed relay went kaput.
 

98stangv8

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The high speed relay in the CCRM isn't working.

The low speed fan runs at idle or normal operating temps. Once the AC is turned on the high speed takes over. If it is shutting off when the AC is on I'm betting the high speed relay went kaput.
Could you help me locate that? The only relay I have checked is in the box under the hood..the big fuse...
 

COramprat

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The high speed and low speed relays are in the CCRM...it's not the fuse box you are thinking. It is mounted inside of the passenger side fenderwell. You have to remove the wheel and splash guard to get to it. It is all one unit so you would have to replace the whole thing. Some call it the "brain", especially if you search for one on Ebay but basically it is a circuit board with 4 relays inside a sealed black box.

IMG_2709_550px.jpg
 

98stangv8

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The high speed and low speed relays are in the CCRM...it's not the fuse box you are thinking. It is mounted inside of the passenger side fenderwell. You have to remove the wheel and splash guard to get to it. It is all one unit so you would have to replace the whole thing. Some call it the "brain", especially if you search for one on Ebay but basically it is a circuit board with 4 relays inside a sealed black box.

IMG_2709_550px.jpg

awesome...great info!

This is just something that I can swap out directly with no issues...ie..walk into Ford and say, "give me one of these" and then go home and plug it in?

Thanks!
 

98stangv8

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Does this same thing also have anything to do with rear O2 sensors? My mechanic told me my rear one is not reading..sensor and wiring are fine..told me it was the computer itself...

Is he referring to this one or a different one?

Thanks!
 

GT Tommy

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Hi Speed Fan not working?

You need to double check your 50 or 60 amp fuse, whatever your system has. Physically remove it, then test it with a multi tester for contiinuity. You also need to disconnect your fan wire connecter and clean out the terminals with an electrical spray cleaner and wire brush. We had the same problem that you are having. We were blowing our 60 amp fuses one after another. Same thing happens, only the low speed fan will come on. When the ac is turned on the high speed fan is suppose to kick in, it didn't. We disconnected the fan wire connector, cleaned out the teminal pins with an electrical contact spray and small wire brush. You may want to test the low and high speed sides of the fan while you have the wire connector disconnected. Run jumper wires straight from the battery to do this. Check the wire diagrams above to see which system you have, so you know which wires are the postives and negative. If both the low and the high side of the fan works, then you can look elsewhere for your problem. We then installed a 60 amp breaker in place of the fuse. This was over two years ago. So far, no more problems with the fan circuit. Both fans come on when they are suppose to. The Constant Control Relay Module in the picture that someone provided, does not have anything to do with the 02 sensors. It only supports the fan and fuel circuits. It's a multi type relay system. On the early models, I believe it is under the driver seat, on the later models it's under the passenger side fender, between the fender, and fender well, just above the strut housing. I believe your 02 sensor problem is another matter. This Constant Control Relay Module, is not your main Computer. Your main Computer is located elsewhere. Good luck, Tommy.
 

COramprat

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As above check the terminal to the fan 1st before you try replacing the CCRM. Could just be the high speed side of the fan has fried. I don't remember what color wire was for low or high speed but you can pick up a Haynes or Chilton's and it is in there. You can test with a voltmeter to see if you get voltage at the harness. You should have power at the terminal on the low speed side once the car is at operating temps and then check the high speed side by turning on the AC. The high speed side should kick in shortly after the AC is on and you will get voltage there. If you get voltage on the high speed side then it is something wrong with the fan. Check the terminal prongs there like in the above post. If they are clean and not loose then the fan is probably bad. You can jump wires from the battery to the fan to see if it will run on low speed and high speed also. If it does then the fan is OK.

If you don't have voltage on the high speed side of the harness then it is in the CCRM. Ford will prpbably have one but you will pay for it. Find a used one on Ebay to save some cash.
 

GT Tommy

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1998 GT Mustang fan circuit

I found another fan circuit diagram. This one is for your 1998 GT Mustang. Notice that besides the 60 amp fuse, their is also a 30 amp fuse in the fan circuit. You may want to check on this. I replaced the diagram with this one, which has a better format for viewing. Click on the bar above the diagram to make it larger. The 30 amp fuse is in the lower left hand side of the diagram. Good luck, Tommy.

1998GTMustang46CoolingFanWiringDiag.jpg
 

COramprat

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If the fuse was blowing then the fan wouldn't run at all. The things to look at in order...

Connection...check to make sure the harness is tight and the fan connector isn't loose.

Test the fan...run jumpers from the battery to the low speed and high speed side of the fan term to see if the fan runs. If not...the fan is bad.

Test the voltage to the fan harness. Get the car to operating temps and check the voltage on the low speed side (should be OK since it runs when the car is at idle). If you have voltage then turn on the AC and check the high speed side. If you don't get voltage to the harness then the CCRM might be bad.