Radiator Fan Problem - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-14-2002, 11:07 PM   #41
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Good idea, Will. I'll try the boiling water experiment. It'* probably going to be Thursday evening before I can play with it, though... tomorrow and Wednesday nights, I have to some "Dad" things. I'll get back to you, with the results.

Thanks

-Roger
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Old 10-20-2002, 05:31 PM   #42
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Will and Rat -

Bad news and good news.

First, I purchased a new Coolant Sensor. Before I installed it, I tried the boiling water experiment, to see if I could get the low speed fan to come on. The wiring harness doesn't provide much slack, but I was able to squeeze a cup of boiling water in there, under the throttle and vacuum hoses, and I dunked the new Coolant Sensor for awhile. No joy... couldn't get the fan to come on. Which made me worry that there could still be something wrong upstream.

So, what the heck... I just replaced the Coolant Sensor, anyway. Guess what... it worked! Temp cycles up to almost 220, low speed fan(*) come on, temp falls back to 200, fans drop out. And the low speed is on both fans, not just the drivers side fan. So, maybe the fan relays are wired so that one relay is low speed (both fans) and the other relay is high speed (both fans)... not sure about that, but I wouldn't be surprised.

Anyway, problem solved... thanks for all the help.

BTW - I'm still planning on a 180 thermostat, but will probably wait until spring.

-Roger
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Old 10-20-2002, 06:00 PM   #43
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Good deal! I'd be curious to see what both thermistors read while at the same temp. Did you try that?

Yes, you're right about the schematic. Both low, or both high. Low and High relays. Thanks for the extra knowledge!
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Old 10-20-2002, 06:46 PM   #44
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I got a problem now , Last week the car would run at around 170 degree'* now it'* gone up to 200 degress'* . Before the fans used to be on mostly all the time , now I can only catch them on with the A C , is this normal or shoul they be on only at high temps , Like I said they used to be on mostly all the time

P * - how much did you pay for the coolent sensor?
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Old 10-20-2002, 07:07 PM   #45
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vze3r85p -

Just to recap what we learned in this (long) thread:

- Fans will always come on (high speed) when the AC is on, or the defroster is on. This mode bypasses the coolant sensor.
- With AC or defroster off, (low speed) fans should come on at about 220 degrees, and shut off at about 200 degrees.

Maybe the reason you heard the fans on all of the time until recently.. was because you had the AC on all the time. That'* what happened in my case... I didn't realize I had a cooling issue until the fall, when I quit running the AC.

I'd have to go back to look at the price on the coolant sensor, but as I remember, it was relatively cheap. Maybe under $20.

-Roger
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Old 10-20-2002, 08:46 PM   #46
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Sounds good to me.....maybe I should move some of this up to Techinfo?
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Old 08-19-2006, 04:59 PM   #47
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Quote:
Originally Posted by willwren
About every 20 change equals about a 100 ohm difference in thermistor resistance. For instance, 212F is 177 ohms, and 194 is 241, 176 is 332, and so on. As you get to the bottom of the scale, it'* not so linear, but we don't care, because the fans come on at the higher range, right? So if you want your fans to come on at 20 cooler, you simply splice a 100 ohm resistor in series with the thermistor. The same trick can be done with the IAT.....if fact, kits for the IAT are sold commercially. You can do it yourself quite simply. Try this one.......you can use a switch to make them come on when you want, but then again, auto is better.
I am going to try this... but this doesn't make sense Bill. If we are trying to "trick" the computer to thinking it is hotter than it really is, shouldn't the resistance be LESS? not more? if it is 212 at 176 ohms if we add 100 ohms, wouldn't that be 276 ohms? which would be showing a MUCH cooler engine? that would be in series... how about in parallel? let me know before i start cutting wires! Thanks
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