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Electric fans won't run, 98 Monte
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Bruce57
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Dec 16, 2008, 7:51 PM
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Electric fans won't run, 98 Monte
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Our 98 Monte Carlo's 3.1L engine cooling fans won't run. Last spring we had an intake gasket leak repaired by a local tire shop, then drove the car almost 400 miles on vacation & noticed it wasn't cooling properly- no fans- once we started getting into some uphill roads. The local Napa store sold me two relays, which I put in the passenger side underhood fuse/relay box, fan control #1 & fan control #2, and they started immediately. This fall, the engine developed another leak, this time around the front cover; I took it back to the same tire store (a mistake, but they're good people). They did a diagnosis on it but said they would not tackle the job. Later that day I drove the car a little & noticed the fans would not run again. I figured no problem, go after the relays again. I did the front cover gasket replacement at home- took everything down, oil pan loose, step by step with a repair manual. Car is back together now, runs well, no leaks, but I've got an issue still with the fans. I looked at each fuse- fan control #1, 30a fuse, it's fine; I replaced both relays in the passenger side box again- temporarily- no change; I checked each relay by going across with a jumper to hear them "click"- all seemed to work fine. Also checked each fuse and relay in the driver side fuse box, same result, nothing blown, relay clicks. I then replaced the engine temperature sensor in the intake manifold valley- no change. After each change I started the car & let it warm up; each time the temperature gauge continued to climb past 3/4 scale- normally the fans would kick on at about 1/2 scale, if I remember right, and stay there routinely. The radiator appears full, and the recovery tank is at the cold fill mark.
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Loren Champlain Sr
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Dec 16, 2008, 8:02 PM
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Re: Electric fans won't run, 98 Monte
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There may be a coolant fan switch which 'tells' the computer when to turn the fans on. Usually, around 230-235f.
If you put the heater control into the A/C or Def. mode, do the fans come on? They should. If not, check to make sure you are getting 12V to the fan(s). <<once we started getting into some uphill roads>> When you are "moving", you don't need the fans. Only in low speed/stopped situations. The movement of the vehicle at normal speeds should be enough to cool the engine. Maybe, you have a thermostat that isn't opening all of the way? But, the fan(s) should be coming on once it reaches the 230-235F point.
Loren
SW Washington
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Bruce57
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Dec 17, 2008, 5:03 PM
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Re: Electric fans won't run, 98 Monte
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Loren, thanks for the tips. I'll check and see if they come on with the a/c on, and try to see if 12v is getting to the relays in the fuse box. Now if I just had a good heater in the garage.....
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Loren Champlain Sr
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Dec 17, 2008, 5:34 PM
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Re: Electric fans won't run, 98 Monte
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Actually, with the ignition turned on, and the heater controls turned to Def. or A/C, you should have 12V going to the fan motor. If not, then check relays. GM relays are mostly the same. You can take one and swap it with another...quick, easy, check. If you do have power and ground to the fan, then probably a bad fan motor.
I failed to mention that on a lot of the newer vehicles, the PCM will command fan operation, but we're getting ahead of ourselves, there.
Loren
SW Washington
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Bruce57
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Dec 20, 2008, 8:39 PM
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Re: Electric fans won't run, 98 Monte
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Finally got back to checking out the beast again. I couldn't get any voltage to the fans, even with a/c or heater on, engine running or not. I tried different settings- no luck. Also tried taking horn relay and switched it with identical fan relays (2 of 3 are same). Still no luck. I let engine heat to far right, getting close to the red zone, still no fans. I took a 12v test light to some of the relay connections, maybe that will help me track where the voltage is losing a connection along with the diagrams in the Haynes manual. Also I went back and spoke to the tire shop that did a diagnosis on the car last time when it appeared to me the fans quit; they said they do several checks on cars every day using their diagnostic engine light checking tool without any problems. One question- if a thermostat sticks closed, the fans should still come on since the engine is running too hot, I assume? The lower radiator hose gets very warm; the upper hose stays very cool. Thanks again for any tips you can offer.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 21, 2008, 1:01 AM
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Re: Electric fans won't run, 98 Monte
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Bruce57: Sorry to jump in and may have been said but I missed it.
Heat from engine should open thermostat, usually right at engine on UPPER hose and on to radiator which cools and returns thru lower hose. If thermostat failed to open the hose would not be hot the lenght of it and rad would be confused/cool and possibly the lower hose would get hot by the time coolant boils things could get backwards I suppose.
As Loren said, anything that triggers A/C frequently forces a fan on - one of the two if two are used BUT some are disallowing the fan is there's no warm compressed refrigerant (freon) which there might not be at lower temps as sensed by the HPCO (high pressure cut out - three wire) on high side line. Never mind all that but note that jumping or even testing three wire switches can blow your PCM - avoid that, kinda wrecks the holidays!
At this point I trust the relays as you've tried new ones in the history - right?
There are temp sensors and combo temp switches that do some magic here. See if this shows..........note three pins inside and plug configuration........
Duralast / Temperature Switch  for a 1998 Chevrolet Monte Carlo 
Related Parts  Coolant Temperature Sensor  About this product: Part Number: TU178 Weight: 0.11 lbs.  Pricing: $18.99  Availability: Store: Normally stocked at your local store. Online: Ships within 2 business days Shipping Restrictions: - Overnight and two-day shipping are not available for PO Box, APO/FPO/DPO or US Territory addresses
************
Note that one has THREE wires! I think this one triggers fans and may also be for your gauge. I plead IDK for sure. It's cheap anyhow and usually easy to toss.
I've been going thru "YuleTide" hair loss with wire plug ends on GM stuff lately too. Suckers can look good and not be and when you get a switch you may find a pigtail in the box or one listed or suggested with the purchase.
That's a common TWO wire one for many GM sensors - not the exact for this car's problem at the moment IMO. When/if these are needed I suggest soldering them in nicely.
**************
Back: Noting the lower hose getting hot while upper stays cool is a bit too interesting - allbeit not funny right now. Would compel me to change out thermostat just from that note! Heat rises so this is inconsistant?? If boiling - I guess bets are off. Is belt ok and you won't see it but water pump might not be pumping well. The pump on the 3.1 is a real easy one usually - gasket scraping takes longer than replacement - no special tools if that's even a possiblity. Guess you really would't know without looking at it but may express itself as poor heat when RPMs are lower and or temp high at idle and better with some RPMs without regard to fannage.
Other: Test light checks:: Again - watch out for possible back powering these three wire items by test light or jumper testing. Even WallyWorld has a $5 +/- led test light that should minimize chances of trouble - great for checking fuses too.
This one is cool! Does red/green for polarity testing when reversed - how festive
I know the timing stinks for car issues but avoid letting this overheat as that just adds more troubles. Also - pay attention to maintain anti-freeze concentration at enough but not to exceed 50/50.
Ps: Loren - sorry to bust in on your thread again! Can you tell I'd rather type than go shovel more dang snow?
T
(This post was edited by Tom Greenleaf on Dec 21, 2008, 1:11 AM)
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Loren Champlain Sr
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Dec 21, 2008, 8:48 AM
Post #7 of 7
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Re: Electric fans won't run, 98 Monte
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Tom; You know the old cliche': Two heads are better than one!! (unless they're on a snake)
Loren
SW Washington
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