fan won't kick on

My 92 Saturn was having an overheating issue, we found that the fan wasn't
kicking on at the appropriate time but when we connected the fan to direct
power it was working. We checked the wires leading to the fan and all but
can't seem to find why it won't kick on. I have it temporarily wired
directly into the fuse box so when my car is running the fan stays on all
the time. This is an ok temp fix but I'd like to get the the solution. Any
suggestions?

 

Mine quit (fan motor after 10 years), but on the '94 it is powered by a
relay in the under-the-hood fuse holder. I rotated the relays first to no
avail (the have the same numbers so test rotation is okay). The relay is
tripped via the computer which relies on several engine temp sensors. If
the relay swap doesn't work, maybe one of the sensors is shot. I doubt if
the computer is gone as other issues may also show up.

B~

 

If you have A/C in the car, turn on the A/C, and set the fan control for
the vents to a position besides 'off'. The radiator fan should come on,
along wiuth the compressor. The car has to be running for this

If this is ok, then the problem is the sensors in the head - there are
two, one controls the fan, the other controls the temperature gauge.
Not expensive to replace both - they're like $10 a piece - and it's easy
too - let the car cool totally, use a 13mm (?) deep socket, and put a
dab of thread sealer on the threads of the new one.

The fan's controlled by the computer - and the computer turns it on via
a relay. If the A/C check didn't turn on the fan, then the fan relay is
bad - the fan ALWAYS runs when the A/C is on. If you want to get rid of
the temp wiring you put in, and the A/C check works, you can unplug the
compressor lead at the compressor, so it won't go on, and you can turn
on the A/C to turn on the fan. Of course, it's better to replace the
sensors

Don't forget to check the obvious - the fan fuse And, IIRC, the fan
relay's the same as a few others, so you can swap two relays and see if
the fan works. Then it's just a relay - easy check.

If you're good with a meter, you can check the wires to the relay and
the power for it, too.

 

If this is a SOHC engine if you look on the driver side just below where the
rad hose from the rad connects you will see two plugs going to two sensors.
The sensor with one wire drives the temperature gauge and the sensor with
two wire plug is the coolant sensor that tells the computer the coolant temp
and turns the fan on. You can verify this by removing the plug with two
wires and you can short out the two pins with a small paper clip or staple
(you simulate zero resistance or very high temperature) and when you turn
the engine on the fan should operate. If the fan works then you know for
sure it is the sensor. Just get a new coolant sensor at the dealer and
replace it (I think you need a deep 10mm socket) and you are all set. Don't
worry about loosing too much coolant when you remove it, just have the new
sensor ready to install when you remove the old one and you will probably
only loose about a couple of ounces. If the fan does not work then you have
to look at the fan relay or fuse because you have already verified that the
fan is good.
Alex

 

Those motors are wear items, and when they fail, they go intermittently.

If you haven't replaced the fan motor, replace it. It's almost certainly
worn out.

 

I concur. Coolant temp sensor. Mine kicks on a little later than when new
(the temp gets all the way up to 3/4 on the gage), but it works fine. $13
for the part. 30 minutes to fix.

Change it on a cool engine. Coolant will leak out of the little hole while
the sensor is being replaced...so have the new one ready once the old one
comes out.

Good luck.

B

 

I'd change out the temperature sensor (the two wire one!) first for sure as
has been suggested. There is, however, still the possibility that the PCM
is at fault in being able to turn the fan on via the A/C but not in
response to the temperature sensor.

 

I'd change out the temperature sensor (the two wire one!) first for sure as
has been suggested. There is, however, still the possibility that the PCM
is at fault in being able to turn the fan on via the A/C but not in
response to the temperature sensor.

 

You can remove the plug going to the two wire sensor and with a staple make
a small jumper and plug it in the two pins simulating a very hot condition.
Now if you turn the car on the fan should come on. If the fan does not come
on then you have to have a meter to start measuring if you are getting
voltage from the battery to the fan.
Alex