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One fan only

24K views 14 replies 7 participants last post by  retiredpauly 
#1 ·
Hope all is well with everyone!

I recently noticed my tempreture was redlining. I checked under the car and hood to see if there was any fluids or breaks in the hoses, and there was nothing. I then noticed that only fan#2 on the passenger side would come on after the temp was hella high then the temp would lower. I also noticed fan#1 never came on at all.

I figured the relay, fuse or motor was out. I checked them all and they turned out ok. I removed fan#1 and conected it to fan#2's conector and the fan#1 worked. I replaced the relay and fan#1 still didnt come on.

My boy did a little wazzu thing where he took some wire and by passed the relay at the fuse box and fan#1 ran and stayed on even with the ignition turned to axilary. We used a test light at the electrical conector, the relay terminal and it checked out good, however fan#1 will not come on.

I looked in the Haynes manuel and it said something about the coolant temp sensor posibly being a factor after runing these test, but I cant see how. Does anyone know what could be the problem and if there was a short circut, why would fan#1 come on after my friend bypassed the relay?
 
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#7 ·
"Fan #2" on the passengers side, is actually the PRIMARY fan. Are you sure you are messing with the correct relay? The fan doesn't come on, until the car gets really hot. I want to say the primary comes on around 220* or so, and the secondary is around 230* or so.
 
#11 · (Edited)
I was assuming it was a 94-96 B-body, with an LT1, and no towing package. They all are setup the same, in the this area.

The fan on the drivers side will not come on unless the pass side fan can't keep the temps under control, or get the A/C head pressure under control. When you unplugged the sensor at the WP, you put the car in a limp mode, protection mode, whatever you call it. The PCM doesn't know what temp the engine is running at, so it kicks both fans on.

The gauge on the dashes of these cars(Roadmaster, Caprice, Impala SS) can be hard to trust. It's sweep from "Cold" to "Hot", might not be that much of a difference in actual coolant temperature. I'm not familiar with how close the 96 SS gauge is, since it is different than the 94/95 Impala SS cluster, which is the same as the ones in my 94-96 Caprices. Cruise down the highway at about 75mph, and see where the gauge runs. At that speed, there is enough airflow, that the fas are not needed. I can't remember the speed thresh hold for the fans to turn off, but I'm fairly certain at 75mph, they are off. Typically, the car will run about 15* F, higher than the t-stat opening temp. So for the factory 180* stat, that is about 195*. When I do this, my 95 Roadmaster runs at about 175*. I know this, because I can go into the climate control, and get an actual reading the PCM see's. In *C. Both of my Roadmasters have a 160* stat in them. This Roadmaster doesn't even HAVE a primary electric fan. It has the towing package, so it came with a primary mechanical fan. I removed this fan, put the primary electric fan on, and never wired it up. Even while sitting for long periods of time, the secondary fan doesn't kick on often.


The gauge on the dash, gets it's reading from the sensor in the passengers side head. I strongly suggest swapping that one.



Oh yes. The Reverse cooling is great. The engines can get really hot, and the heads are cooled first. The T-stat is 180* stock. But, it doesn't hit 180*, and then fly open. It has a dual element, so it opens slower. It is also effected by the "cold" side. But, the programing in the PCM is set so the fans don't come on until the engine really gets hot. I think the temps are actually 224/234* F for the primary/secondary fans to kick on. There are a few reasons, why we think GM did this. The hotter the engine, the lower the idle emissions. Less wear on the fans, so they will last longer. Who knows. But on the flip side... LT1's LOVE to run ice cold. The colder you have them run, the more power they make. These engines feel slow, as if they have lost quite a bit of power, when they are running around 230*. At the points when the secondary fan actually kicks on, you can tell the motors are hot. A simple reprogram of the PCM can change this, so the fans come on sooner.
 
#10 ·
I forgot to include that my car is a 96 Impala. Ok I did not know that fan#1 was on the passenger side. The fan on the passenger side always comes on, but it does so at about damn near the redline, and the fan on the driver side never comes on even at damn near red.

But something intersting happened 2day. I disconected the electrical conector of the coolant temp sensor and both fans came on and stayed on. When i reconected the sensor, the fan on the driver side immediately shut off and never came on. I changed The coolant temp sensor and still nothing. No check engine light is on Im having a problem finding whats causing both fans not to run when the car runs hot. When I run the AC only the fan on the passenger side comes on. I checked both relays and the are good. I even changed the relays and the fan on the driver side still don't come on.
 
#12 ·
Hey yall check this, I forgot to mention that I have recently replaced the water pump and thermostat. Ive been reading threads on here where guys have said, you need to bleed the cooling system at the thermostat housing when changing it. Could that also be a overheating problem?
 
#13 ·
Sounds to me like the car is acting completely normally. You would not be the first to freak out over how high GM set the fan temps on these things.

On the highway forward motion will move enough air to keep the engine roughly 30degrees cooler than the primary fan on temp so when stopped and the engine is allowed to come all the way up to that on temp the needle is a LOT higher than you see it when moving at a decent speed.
 
#15 ·
Put your AC on and see if it comes on. I think it will run the whole time the AC is on. It will also come on if the car is REALLY hot.
The drivers side fan only is usually enough to control temp W/O AC.
 
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