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cooling fan problems


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12 replies to this topic

#1 bushbasher

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Posted 25 October 2003 - 06:48 PM

I can't figure out why my electric fan is not turning on. First, I found that the temperature sensor in the rad had a wire broken off, so I soldered it back on. Now it reads around 20m ohms when the car is at 1/2 heat. I put a voltmeter to the wires to the sensor, and they recieve 0.2v, and when the car is off 0 volts. The fan also works fine itself. What reads the sensor, is it the computer, or just some relay type thing? All my fuses are good, but since that wire came off it could have shorted on something, and damaged whatever reads the sensor. Any ideas?

#2 bushbasher

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Posted 25 October 2003 - 09:45 PM

qmud

#3 subynut

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Posted 25 October 2003 - 10:45 PM

The sensor controls the fan directly. At least it does on my '86.
If the 20m means 20 Meg-ohms then, yes, that sounds about right. The fan goes on at about 3/4 on the guage or about 210 degrees.

#4 bushbasher

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Posted 25 October 2003 - 11:05 PM

I had my car almost in the red, with no go for the fan. Shouldn't the sensor be recieving more than .2v? shouldn't it be 12v?

#5 bushbasher

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Posted 25 October 2003 - 11:29 PM

Oh I think I get it now, the thermostat is actually a switch itself, not a varying resistance deal? If that is so then I should definitely be getting 12v to the switch, but I am not. Still need help!!

#6 TomRhere

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Posted 26 October 2003 - 05:40 AM

The thermatic switch in the radiator does just what you said; Turns the fan on at 1??* temperature.
It is the ground for the fan circuit. Therefore you have to insure a good electrical connection between the radiator and the battery -.
You can check the fan operation by grounding that wire going to the switch; to the body, or the battery.
There should be a wire attached to the upper stiffening rail of the radiator, and going to the body. It's just a short length of wire. Even if the wire looks ok, there could be corrosion at either end of it. Break the attaching screws loose and retighten them.
You won't have good continuity thru the switch until the engine gets to about 3/4 of the guage. Atleast that's when the one in my BRAT comes on.
Hope this helps.

#7 bushbasher

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Posted 26 October 2003 - 07:55 PM

just wired the fan to be on whenever the engine/ignition is on. It gets up to 1/2 quickly and stays there. It rarely goes below freezing here, so it should still be able to heat up in the winter. It also keeps me from ever leaving the ignition on, because I can hear it. There is an override switch in the engine compartment now.

#8 TomRhere

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Posted 26 October 2003 - 08:04 PM

That will work. Could even splice into that wire for the switch on the radiator, run it into a switch on the dash, then to a good ground. Read a few posts on here of guys doing that.
Few years ago, I had a 3/4T Ford 4X4 351W/C6 Auto. Had to put an electric fan on it due to clearance issues. Only time I had to flip the switch for the fan was when I sat in-line at the Bank's drive-thru.
Short stops at idle, or driving down the road, you really don't need the fan.

#9 bushbasher

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Posted 26 October 2003 - 08:26 PM

The only reason I don't want a switch in the dash is because I might leave it off and forget it, or if someone else drives it he or SHE won't remember about it even if I repeat it over and over.

#10 subynut

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Posted 28 October 2003 - 12:47 AM

You mean like I did the other day. I went to town to drop off my used oil at pepboys and when I turned the engine off it made this crack pop crackle sound! :cornfuzz: Curious, I turned the engine back on and HELLO!!!! the h2o temp guage is sittin up at 280!! :dead: DOH! :banghead: Turned the fans back on and let her cool off and she's been ok since, but yeah, kina scary. oops:-\

#11 Aces Full

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Posted 23 March 2009 - 12:41 PM

I've got an '89 DL. My electric fan also does not switch on. I'm assuming that my car has the same sensor in the radiator. What part of the radiator do I need to look at for this sensor and how do I test it?

Thanks in advance!

#12 Gloyale

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Posted 23 March 2009 - 12:55 PM

I've got an '89 DL. My electric fan also does not switch on. I'm assuming that my car has the same sensor in the radiator. What part of the radiator do I need to look at for this sensor and how do I test it?

Thanks in advance!


Look on the passenger side, about half way down. Should be an open circuit across the 2 poles when cold, and closed when hot.

#13 subieman666

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Posted 23 March 2009 - 05:37 PM

the easiest way to get around the fan not turning on is to toggle switch it, i have done it in all my subies i have owned, it seems to be a big problem with the 80's subies idk about any of the other era's since i have only ever owned pre 85 subies




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