Rad fan not coming on

[shwartzbewithyou]

My Rad fans not coming on and I have yet to check all the wondrous thermo switches we have on these cars.  So let me conclude by just asking does the thermo switch that is in the bottom corner of the rad seal in fluid?  Do I have to drain the system to pull out that switch or is the switch self contained inside another compartment in the rad?

Can I test this switch and the other by just pulling the plugs and grounding the leads together (assuming that it's only a 2 pin switch) and if it goes then that would say that the switch it's plugged into is probably bad or not making contact?

Thanks

[jtanguay]

To change that temp sensor you need to drain the rad fluid.  First things first, trip your fan with 12v supply and make sure it actually works.

The fan temp sensor switch has 2 modes, for hi/lo operation of the fan.   So it is 3 pronged.  Your best bet is to get a multimeter and run the car until the relay kicks in.  If it doesnt then you have a bad relay.  Hope it isnt the thermo switch, or worse the FAN!

make sure to clean the contacts with something, wd40 seems to work best

[shwartzbewithyou]

Is the termo switch expensive?

[jtanguay]

shouldnt be more than 30 bucks?

[chrissev]

To change that temp sensor you need to drain the rad fluid.  First things first, trip your fan with 12v supply and make sure it actually works.

The fan temp sensor switch has 2 modes, for hi/lo operation of the fan.   So it is 3 pronged.  Your best bet is to get a multimeter and run the car until the relay kicks in.  If it doesnt then you have a bad relay.  Hope it isnt the thermo switch, or worse the FAN!

make sure to clean the contacts with something, wd40 seems to work best

you don't really need to drain the coolant to replace that switch.  When you thread the switch out, stick your thumb over the hole to keep the coolant in (do this when the engine is cold, been sitting for a long time) then take your thumb out of the hole and thread the new switch in.  You'll lose a small amount of fluid but it's not worth the trouble to drain the whole system.

[shwartzbewithyou]

Well I'm pretty sure i've narrowed it down to the swithc in the rad.  I pulled the harness off of it and jumpered it and the fan came on.  So either the switch isn't triggering, or the rad isn't get hot enough to trigger it, which would tell me that the thermostat is stuck shut and thus not circling fluid through the rad (now that's a run onn sentence)....however, if that was the case then the temp wouldn't go down when the car started moving again.  So anyways I have a manual switch to trigger the fan that will get me through or at least until I'm finished some house renovations and thus have time.

[Methanolab]

Is there any way to test the relay? I think I am having this same problem. I have an '83 quantum with two fans. I thought I have heard/saw one come on since I got the car a couple months ago. But recently the temp gauge has gotten up to 3/4, while the car was sitting still and I was revving it, without a fan kicking on. The car's moving-operating temp is about 1/4 of the gauge.

[shwartzbewithyou]

Well there is but I find it easier to test the rad switch than the relay.  Just jumper the wires.  Any red to the brown (2 and 3 pin type)
If you want to test the relay you'll have to find what pins are for what on it and then feed it power and listen for a "click".  I'm not sure where you could get a schematic for it, mine had one on the side but I couldn't read it well enough to understand it.  Also I'm not sure if their would be some type of resistor cirquit in line before the power gets to the relay or is it a full 12VDC relay....?  If it's not then jumpering wires to the battery might confirm that you need a new relay because it might smoke right there in your hands.

[shwartzbewithyou]

So I just pulled the plug off of the temp switch in the rad and put a manual switch on my dash for now.  I found a perfect switch on an old intercom call button (the one's you had on the wall in the classrooms at school) that fit in one of my blanks on the dash perfectly.  It has off, on , and a momentary high postion.
Werks purdy darn good.

[arfalberg]

i also have a fan that does not react to rad temp.  i just turn my fan settings to defrost. normally that would kick in the ac unit and therefor it kicks in the fan.  it works great. plus i do not have to wire in any additional switches.

[LeeG]

who needs a switch?  a real redneck jumps out of the car at a light to jam a bent paper clip into the connector and does the reverse before getting back on the highway!  If I'd actually wired a switch to the dash I probably never would have gotten around to replacing the thermo switch.....which was C$22.  As Chris said, you dont need to drain the rad if your quick and have all the parts in reach.

[jtanguay]

i also have a fan that does not react to rad temp.  i just turn my fan settings to defrost. normally that would kick in the ac unit and therefor it kicks in the fan.  it works great. plus i do not have to wire in any additional switches.

hmmm does your a/c work? if not then I would just suggest bypassing your resistor to increase the speed of the fan for optimum cooling