I drive the car approximately 20 miles to work in city driving. When I get to work (or home on the return trip), I open the hood and notice that the radiator fan is not running. The dash temperature gauge never climbs more than a third of the way up the scale. The outside air temperature for this time of year is over 100 degrees. Things I've checked:

1) Coolant level: good
2) All fuses: good
3) Fan relay: good
4) Fan motor: good
5) Thermoswitch: good
6) Continuity between components: good
7) Followed DYI section on overheating: passed all test

I mentioned that the thermoswitch tested good, but if I short the switch, the fan will run.

Questions:
1)Is there a way to hook up a temperature probe to measure the actual coolant temperature?
2)Is it possible that the coolant temperature doesn't exceed 194 degrees during my 20 mile drives?

Thanks

 

First off,, i wonder if you are aware that the fans do not stay on all the time ,, they come on for a short time, enough to cool the radiator and then they shut off till coolant get hot again,, fans cycle on and off all the time...

Now the quetion i have is this ,, you said ( radiator fan not running ) is the cond fan on when the rad fan is not running ??
also anythime that you short the switch at the t-stat housing the fans will run,, so,, that tells us the the wiring, fuse, relay, and motor are ok..

if fan does not come on at all, and it comes on when you jump the switch at t-stat,, you got a bad switch

20 mile drive should more than get the temp at 194 degr .

also if fan was not working the needle on the gauge would be higher than 1/3 ,assuming gauge and sending unit are working properly

 

The condensor fan is functional, but I don't run the AC since I have a refridgerant leak I haven't located yet. Should the condensor fan run when the radiator fan runs even if the AC isn't turned on? I checked the thermal switch by placing it in heated coolant. The switch conducts and is open at the specified temperatures. That test was done using a hot plate, thermometer, and the switch suspended in a beaker filled with coolant. I wonder if the switch might not be seeing enough coolant when its installed. Is there a way to check the coolant temperature other than the dash gauge? You may be (and probably are) right that the fan is functional. I don't hear it when and if it does engage. The relatively low temperture gauge reading shows that the fan probably is working. I would like to check the actual coolant temperature just for piece of mind.

Thanks

 

If your radiator is in good shape, it's definitely possible for the fans NOT to run. They generally only need to run when the temperature gauge gets somewhat above half-scale. And THAT usually only happens with either of 2 things. Radiator is full of garbage, or you're stuck in traffic & NOT moving.

'93 has 2 fan switches, right? Did you check both? The one in the thermostat housing is responsible for switching the fan while the engine is running, the one in the head is responsible after the engine is turned off.

The best way to check is take the fan switch out, put it in a pot of water with a thermometer, & check continuity while you heat up the water.

 

this is what you do........

start the car up and let it warm up...as it warms feel the lower radiator hose , it should start to get warmer,, when engine is fully warm, the lower radiator hose should feel HOT . if it feels cool or luke warm you got a stuck t-stat

assuming t-stat is ok,, let engine run, after a while longer BOTH fans should come on,,,,,,,,if only 1 fan comes on ,, we need to diagnose why,,could be afuse, relay, motor, wiring

if NEITHER fan comes on,, jump the switch at thermostat housing,, if fans come on you got a bad switch ...



And JIMBLAKE my friend ,no matter how good the radiator is,, the fans will always run ,, you can install a new radiator , let engine warm up and the fans WILL COME ON
the only possible time they might not come on is if it is very, very ,cold outside and you are driving ,, but anytime car sits still the fans will come on

as for testing the switch, no need to remove it and test it,,,,,,,,,if fans do not come on, and engine is warm,, jump the wires if fans come on you got a bad switch ..

 

I'll do the radiator hose check this morning on my drive in to work. When I did jump the thermal switch earlier, only the radiator fan came on. I've previously checked the thermal switch by placing it in coolant and heating it. The switch worked as spec'd. This was of course before I learned that shorting the switch was an alternative to pulling the switch.

 

With my cars I have a hard time getting the fan to run when I'm driving. With the car moving thru the air at even 10 mph, it's got plenty of air so the fan isn't needed. (Well, it runs with the AC...) That's what I was getting at...

 

Jim, you are correct apparently enough air flows to cool the engine even at low speeds that the fan does not come on often. I did let the car sit running and the fan did automatically come on after a while. But Desert Honda mentioned that the condensor fan should also come on, it did not. Recall that the air conditioning is turned off. Should the compressor fan still come on even when the A/C is switched off?

 

OK let me say it ONE LAST TIME............BOTH fans are supposed to be on when coolant reaches a certain temperature,, wether you have the a/c on or not BOTH fans are supposed to come on at the same time ..........

chk to see if you are getting power and ground at the motor that does not work..

if you are,, you got a bad motor

if not could be the fuse, relay, wiring

 

Yes, when the AC is working properly. Check wiring drawing for your year; the AC low-pressure interlock might be preventing the other fan from running. Remember, when the AC is OK, the low-pressure switch is closed even when the AC is switched off.