Coolant Boils, Fan's dont come on
 

On my 95 camry LE 2.2 4 cylinder, the radiator fans stopped coming on and the coolant begins to boil.

I know its not the fan motors because they still come one while the AC is on. And ive replace the radiator, radiator cap, radiator hoses, Coolant temp sensor and thermostat. and ive cleaned out the heater core.

and still the fans dont come on. Any thoughts on what else could be causing this?? Please and Thanks

The fans are controlled in part by a temp sensor on the radiator, did you check this sensor? There are also a few relays in the circuit.

Find the sensor located on the lower part of the radiator facing the engine. Remove the plug from the sensor, the fans should come on with ign switch on.

The Autozone website should have info on testing the sensor in the sites self help vehicle repair guide section.

Alright, i'll have to put my heater core back in and add the antifreeze back in first (which may take me a few days). so when i get that done and test it out. i'll get back to you. But i have replaced that sensor in the radiator maybe it was defective? i dunno, i'll have to look up those tests.

Thank you sir, this is the first forum that actually helped me out. :):):)

Correction: It appears if the electrical plug is removed from the radiator temp switch only the radiator fan will turn on.

The fan system wiring is complex having 3 relays and a high/low speed setting.

The radiator coolant temp on/off switch turns OFF when coolant temp is above 194F, this is opposite of what one would expect. If the plug is removed from the sensor this is equivalent to turning the switch off, the radiator fan should then run.

With the A/C on, both fans should cycle on/off on as the A/C compressor engages and disengages. In this case the fan relay wiring causes the fans to be wired in series and operate at a lower RPM.

There is an A/C system pressure switch that turns OFF if the A/C system pressure becomes higher then 221 PSI. If this happens the relays cause the fans to be wired in parallel and operate at a higher RPM.

Typically the fans run in series.

The system uses 3 fuses, ECU-IG, RDI and CDS Fan, and 3 relays, Radiator Fan (No 1), Radiator Fan No 2 and No 3.

The Radiator Fan relay controls the radiator fan.

The other 2 relays link in for low and high speed fan settings.

Check the Radiator Fan relay operation and circuit by removing the temp switch plug on the radiator. The radiator fan should come on.

Then run the A/C test above.

Check fan operation by applying 12V to the fan plug wiring, if the fans are getting 6.5V when A/C compressor cycles, relay operation.

So i found the bad relay. (it was fan relay 3). Should that fix my problem?? I had to special order one so i wont have it until 2 business days.

But i also have a question about the lower radiator hose. Should it always be fairly cool, or is it suppose to get as hot is the top radiator hose??

The bottom would be cooler then the top as the radiator should have dropped the temperature down. But the coolant in it would still be very hot.

Somewhat confused. Relay fan 3 controls fan operation when the A/C is on.

The relay that controls the radiator cooling fan is located in the engine fuse box, drivers side. Rectangle shape but has one diagonal side.

Did you unplug the connector for the temp switch on the lower radiator and determine if the radiator fan came on?

Yeeah, from what you told me i was a bit confused too. But i checked all 3 relays and 3 was the only one that didnt have continuity.

And i did unplug the temp switch, and the fans came on just fine.

The wiring is confusing unless you have a diagram and study it for a while.

Basically the radiator relay is always on and making a switch connection. It is only when the relay is turned off that the radiator fan comes on. This is why unplugging the temp switch turns on the fan. The switch opens when the coolant temps get about 194F, the open switch turns off power to the relay turning on the fan.

Well i rechecked all the relays. and everything seemed to check out. AC turns on, and i applied 12V to where relay 1 and 2 should be, and both fans came on. I rechecked relays 1 and 2 and they both have continuity.

So the problem still remains. -_-
some other forums keep telling me about a radiator fan switch. but i cant seem to find that becuz all they tell me is that it is located on the radiator. But the only switch connected to the radiator would be the coolant temp sensor.

I stopped talking to them tho, becuz they arent very helpful.

Fan doesnt turn on
 

Fan doesnt turn on.

When the Fan doesnt turn on,
but does Turn On
if you Unplug the coolant temp switch
in the Radiator,
and you have Tested or Replaced
the coolant temp switch,
Then,
Look for Bubbles in the Overflow bottle.

If there are Bubbles in the Overflow bottle,
then the Bubbles are Pushing away the Water
from the coolant temp switch,
and
the Fan wont come on
unless you unlpug the coolant temp switch
or turn on the A/C.


Solution?

Replace the Head Gasket.




Comments anyone?


.