AC Underhood Fan Speed?

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turn_on68

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I need to know if anyone knows about when a Fan gets miles on it if it runs slower or is there a regulator under the hood that controls the fan speed? I am having too much heat in my AC in town which I never had all the years before, but when I am on the hiway the AC almost freezes me out. I got a used fan from Peter and it has less miles on it than mine does, but that didn't fix my problem. I have had the compressor checked, freon level checked all is okay. My thought now is either when these fans get old they have to be replaced ($400+ ) or there is a regulator that controls when to speed up the fan or slow it down? Anyone?:confused:
 
First off what year is your ride? I just went through a fan replacement as mine siezed and the car came close to over heating.

If I do understand the system correctly, the VLCM or VCRM controls the fan but turning on the a/c fires it up right away.
 
LSC HUNTER said:
First off what year is your ride? I just went through a fan replacement as mine siezed and the car came close to over heating.

If I do understand the system correctly, the VLCM or VCRM controls the fan but turning on the a/c fires it up right away.
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mine is a '98. I spoke with Max at FORD in AZ. He told me it could be the VCRM,VLCM,GE Module all names for the same regulator which is no longer available. Do you know if it is an on off or could it be failing to kick the fan into fastest speed? I can get a new Fan assembly, but if the fan works which mine and the one I got from Jaime does, but I never hear it roaring like I think it should? I always was more than cool in town, but now only on the Highway. Do you know as fans get many miles on them do they fail to spin wide open or is that the VCRM not working? Mine had a little scorch mark on one of the pin tabs where to fan plugged into the wiring harness. I cleaned that up put and dielectric grease in it.
 
If you can get someone to turn on the a/c for you while you are observing the fan to see if it kicks up in speed for you. Maybe mark on of the blades with a yellow piece of tape to just give you a visual. Mine just started to act up and the a/c wasn't very cool at all even on the highway. Then one day it just gave up completely and left me on the side of the road.
 
The fan turn off at 45mph I think, even with AC on. There are variables that are programable using software that I have.

You could simple cheat and temporarily apply 12 volts to the fan to get it running. Then drive this way around town. If conditions change then its something controlling the fan most likely. If AC is a little warm, then it could be that the AC system does indeed have a problem.

Then there is the blend door thing. It could be stuck, partially broken, etc. If its not working right its may be mixing in too much city air. Being that the intake is behind the engine, it will be warmer than the actual outside temp. At highway, this is less an issue.
 
unity said:
The fan turn off at 45mph I think, even with AC on. There are variables that are programable using software that I have.

You could simple cheat and temporarily apply 12 volts to the fan to get it running. Then drive this way around town. If conditions change then its something controlling the fan most likely. If AC is a little warm, then it could be that the AC system does indeed have a problem.

Then there is the blend door thing. It could be stuck, partially broken, etc. If its not working right its may be mixing in too much city air. Being that the intake is behind the engine, it will be warmer than the actual outside temp. At highway, this is less an issue.
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Fan runs it just doesn't cool as well in town as it use to. Highway is ok. I have had the AC freon pressures all checked an it is okay. I have plenty of inside fan speed. My suspect is either the VCRM is not going into high speed or the older fans will not spin at top speed?
 
Ya, that can happen. I *think* you can test the low/high speed of the fans by adding 12 volts. If I recall, and someone may want to verify, that the fan connector has three leads. One is ground, one is high speed, one is low speed. I just am not sure if sending power of 12 volts on both power leads will result in the same speed or if the fans themselves have a built-in resistor for low speed.
 
unity said:
Ya, that can happen. I *think* you can test the low/high speed of the fans by adding 12 volts. If I recall, and someone may want to verify, that the fan connector has three leads. One is ground, one is high speed, one is low speed. I just am not sure if sending power of 12 volts on both power leads will result in the same speed or if the fans themselves have a built-in resistor for low speed.
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"Ya that can happen" what? The old fans will not go as fast or the VCRM is not working correctly?
 
I give up. You insist the fan runs fine. Then you think it could run slower? I am not sure of the logic there.
 
unity said:
I give up. You insist the fan runs fine. Then you think it could run slower? I am not sure of the logic there.
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Unity we are miscommnicating. I am saying since 2001 my Mark VIII has cooled exceptionally in town or on the highway. Not this year only really cooling down on highway because of more forced air over AC condensor. So my question was, do these fans slow down as they age so it is not going into as high a speed as it use too and I should invest in a new fan, as opposed to the used one I bought with 70,000 less miles on it, or is it more than likely the VCRM that may be not allowing high speed in town because it is faulty. I have read that the VCRM's go out quite frequently, however I have never had to replace mine yet.
 
pull the sensor plug under the passenger side of the crossover tube, start engine , fan will come on at its highest speed possible, Fan should be very powerful like that,if its not,fan may be dying
 
First off, the fan has a variable speed motor controlled by the VCRM from 50% battery voltage to 100% battery voltage depending on ECT sensor and AC pressure.

The fan wiring harness has 3 wires, but only two are used. The middle wire terminates in the harness. The other wires should be LB and BK. Black is ground and Light Blue is voltage from the VCRM/VLCM.

The fan does cutoff on the highway at 45 mph, unless AC head pressure builds too high.

When the EATC is set to MAX AC, the fan runs 100% full speed.

With age, the fan will get "slower" due to drag. Eventually it will lock up and quit.

You can replace just the fan motor, no need to replace the entire fan assembly. The OEM motor is riveted in place, but the rivets can be drilled out and the new motor bolted in place.

The ground wire is very important. If suspect, attach a separate ground wire to the fan motor.

I hope this helps.
 
Moes8 said:
pull the sensor plug under the passenger side of the crossover tube, start engine , fan will come on at its highest speed possible, Fan should be very powerful like that,if its not,fan may be dying
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Thanks for that suggestion I will try it next.
 
driller said:
First off, the fan has a variable speed motor controlled by the VCRM from 50% battery voltage to 100% battery voltage depending on ECT sensor and AC pressure.

The fan wiring harness has 3 wires, but only two are used. The middle wire terminates in the harness. The other wires should be LB and BK. Black is ground and Light Blue is voltage from the VCRM/VLCM.

The fan does cutoff on the highway at 45 mph, unless AC head pressure builds too high.

When the EATC is set to MAX AC, the fan runs 100% full speed.

With age, the fan will get "slower" due to drag. Eventually it will lock up and quit.

You can replace just the fan motor, no need to replace the entire fan assembly. The OEM motor is riveted in place, but the rivets can be drilled out and the new motor bolted in place.

The ground wire is very important. If suspect, attach a separate ground wire to the fan motor.

I hope this helps.
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Yes thanks, that tell me what I wanted to know. Now where does one find just an exact replacement motor???
Oh this AM 82 degrees out and the AC literally froze me out, i had to reduce the inside fan speed.
 
Moes8 said:
pull the sensor plug under the passenger side of the crossover tube, start engine , fan will come on at its highest speed possible, Fan should be very powerful like that,if its not,fan may be dying
Click to expand...

I just did that and it spun so fast I could see the condensor behind it without any problem. So I assume that is fast?
 
turn_on68 said:
I just did that and it spun so fast I could see the condensor behind it without any problem. So I assume that is fast?
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unfortunately that doesnt fix your problem, but it does show you what your fan is still capable of at 100% voltage.sounds like your fan is still capable of proper cooling,and something else is causing the problem you explain.

next time your a/c isnt cooling well, pull that plug and see how it works when the fan is screaming.

pulling plug causes CEL to light up, fyi.
 
Moes8 said:
pull the sensor plug under the passenger side of the crossover tube, start engine , fan will come on at its highest speed possible, Fan should be very powerful like that,if its not,fan may be dying
Click to expand...

This sensor is really cheap to replace. It has 167,000 miles on it. Is there any reason not to replace it? Maybe it is an either on or off? But if not, then maybe it has some calcification built up on it and might not be responding as quick as it should ?
 
turn_on68 said:
This sensor is really cheap to replace. It has 167,000 miles on it. Is there any reason not to replace it? Maybe it is an either on or off? But if not, then maybe it has some calcification built up on it and might not be responding as quick as it should ?
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replacing parts can never hurt anything, except maybe your wallet, go for it.

My comment about unplugging it wasnt actually meant to imply that sensor was bad,but hey, you never know
 
Have you checked the connections to the fan blower motor under your dash sometimes the connections get crappy. I recrimped mine and it blasted me out of the car in city or highway, in my 1996! My 1998 only drives and power locks still !!! Good luck
 
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