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benwagison · Dec 28, 2011, 05:21 PM

Where is the coolant fan relay switch located on a 1992 honda accord ex wagon with an automatic transmission

TxGreaseMonkey · Dec 28, 2011, 06:09 PM

The Engine Coolant Temperature (ECT) Switch is located on the thermostat housing, while the Radiator Fan Relay should be located in the under hood fuse/relay box.

benwagison · Dec 28, 2011, 07:43 PM

Thanks TX, but the thermostat housing does not have any type of electronics in it. I replaced the thermostat, it is on the back of the engine and is connected to the bottom radiator hose. The housing has a black tube that runs down to it (looks like a vacuum tube) and what I believe is a bleeder valve, but there are no sensors on the housing. I believe the (ECT) is located on the front of the engine where the top radiator hose attaches to the engine block. I'm sorry I misworded my question. What I need to know is where the sensor that signals the cooling fan on the raidiator to turn on?

TxGreaseMonkey · Dec 28, 2011, 07:50 PM

Check out what the ECT Switch looks like at AutoZone.com--Part No. SW546. Then, look for it on your engine. AutoZone also claims it is located in the thermostat housing. It's a switch, not a sensor. Switches have one wire going to them, while sensors have two wires.

benwagison · Dec 28, 2011, 10:03 PM

My apologies TX. The ECT is in the top front, however there is a sensor in the bottom of the thermostat housing that is the fan control switch. I don't know how I missed seeing this when replacing the thermostat. I jumped the conector and the fan comes on. So I know the fan motor is good. I was having trouble with overheating, however, I did not bleed the cooling system after replacing the thermostat. So, I did that today. The car doesn't seem to be overheating now, but the fan is still not coming on. Should the radiator fan come on if I let the car idle for 30 min and it reaches normal operating temperature or does it just come on when the engine gets hotter than normal?

TxGreaseMonkey · Dec 28, 2011, 10:19 PM

I knew that's what you would find out.

. Fill the radiator, until the coolant comes out the opened bleeder bolt. Very important.

. Check that the radiator cooling fan comes on when the A/C is turned on. Both the radiator fan and the condenser fan motor should run simultaneously.

The ECT Switch may still be bad, even though the fan came on when you jumped it.

. Check/replace the Engine Coolant Temperature (ECT) Switch, not the ECT Sensor. To test the ECT Switch, remove the electrical connector. Using a multimeter, set to ohms, check for continuity across the terminals of the switch with the engine cold. The switch should not have continuity, while the coolant is below 189 degrees F. Start the engine and allow it to reach normal operating temperature. Stop the engine and check for continuity again. The ECT Switch should show continuity, when the coolant temperature reaches 196 to 203 degrees F, and above. If the switch fails to show continuity above this temperature, replace it.

If the radiator fan runs all the time, the ECT Switch will likely show continuity below 189 degrees F. This situation will, also, require replacing the switch.

. Check/replace the radiator fan relay, which is usually located in the under hood fuse/relay box. It's easiest to use a Power Probe II, in conjunction with a multimeter. Power Probe II will power up the relay, while the multimeter will test for continuity (ohms).

Only fill your cooling system with a 50/50 mixture of the proper antifreeze and distilled water. If you use tap or well water, the antifreeze will form phosphate scale, which will block off passages in the radiator and heater core. It will also form on the thermostat, ECT Switch, and ECT Sensor. Otherwise, buy prediluted coolant.

benwagison · Dec 31, 2011, 06:44 PM

TX. I replaced the ECT switch. However, the fan still does not come on even when the engine gets hot. The engine got so hot today that I had to turn the heater on full blast to pass air through the heater core and cool it down. Also, the neither fan comes on when the AC is turned on. However, both fans come on when jumping the connector for the ECT switch. I have simply jumped this connector so the fan runs continuously when the ignition is turned on. I am hoping this is just a temporary fix. Do you have any idea what is causing this?

TxGreaseMonkey · Jan 1, 2012, 05:58 AM

. Check all under hood and under dash fuses with a test light or multimeter.

. Remove and clean the ground terminal on the thermostat housing; afterwards, apply dielectric grease.

. Check/replace the radiator fan relay, located in the under hood fuse/relay box.

. Test the new ECT Switch, as previously described. Make sure you bled air, again, after replacing the ECT Switch.

. Examine the ECT Switch connector and wiring.

. Check/replace the ignition switch for wear and pitting, if the problem persists.

Coed_naked · May 22, 2012, 09:53 PM

I have a similar problem with my 92 accord... It overheats and the cooling fan doesn't come on but when I turn the car off it turns on... I know for sure it's not the fan or the relay that's bad... Seems like either the sensor or the thermostat... Any help on fixing this would be appreciated... Another thing if I were to bypass the thermostat or the sensor and install a manual toggle switch for the fan, would that be a viable and cheap fix?

CaptainRich · May 23, 2012, 05:29 AM

Originally Posted by Coed_naked

I have a similar problem with my 92 accord... It overheats and the cooling fan doesn't come on but when I turn the car off it turns on... I know for sure it's not the fan or the relay thats bad... Seems like either the sensor or the thermostat... Any help on fixing this would be appreciated... Another thing if I were to bypass the thermostat or the sensor and install a manual toggle switch for the fan, would that be a viable and cheap fix?

That could be a viable and cheap fix but only if that is what is needed to correct the problem. I tend to think that once the fault is diagnosed, you will likely find it easier and faster to simply replace the failed component rather than tap into the harness somewhere, run a fuse protected circuit to a switch you'll need to mount somewhere convenient and then keep a close eye on the temp gauge.

Your first next step is a genuine diagnosis.

Coed_naked · May 23, 2012, 05:51 AM

Originally Posted by CaptainRich

That could be a viable and cheap fix but only if that is what is needed to correct the problem. I tend to think that once the fault is diagnosed, you will likely find it easier and faster to simply replace the failed component rather than tap into the harness somewhere, run a fuse protected circuit to a switch you'll need to mount somewhere convenient and then keep a close eye on the temp gauge.

Your first next step is a genuine diagnosis.

Thanks CaptainRich but in your expert opinion what would u diagnose the problem to be from info provided in the previous post?

TxGreaseMonkey · May 23, 2012, 06:54 AM

Coed, it's a downward spiral, once you start "jerry rigging" a car--you never want to do that. Unforseen events will overtake you. Good diagnosis is the proper course. With that said, I would locate and test the Engine Coolant Temperature (ECT) Switch, not the ECT Sensor. The ECT Switch is usually located in the side of the thermostat. To test the ECT Switch, remove the electrical connector. Using a multimeter, set to ohms, check for continuity across the terminals of the switch with the engine cold. The switch should not have continuity, while the coolant is below 189 degrees F. Start the engine and allow it to reach normal operating temperature. Stop the engine and check for continuity again. The ECT Switch should show continuity, when the coolant temperature reaches 196 to 203 degrees F, and above. If the switch fails to show continuity above this temperature, replace it.

Coed_naked · May 23, 2012, 09:21 AM

Originally Posted by TxGreaseMonkey

Coed, it's a downward spiral, once you start "jerry rigging" a car--you never want to do that. Unforseen events will overtake you. Good diagnosis is the proper course. With that said, I would locate and test the Engine Coolant Temperature (ECT) Switch, not the ECT Sensor. The ECT Switch is usually located in the side of the thermostat. To test the ECT Switch, remove the electrical connector. Using a multimeter, set to ohms, check for continuity across the terminals of the switch with the engine cold. The switch should not have continuity, while the coolant is below 189 degrees F. Start the engine and allow it to reach normal operating temperature. Stop the engine and check for continuity again. The ECT Switch should show continuity, when the coolant temperature reaches 196 to 203 degrees F, and above. If the switch fails to show continuity above this temperature, replace it.

Thanks man... Could you let me know where the thermostat housing will be because some say it's by the top hose and some say it's by the bottom hose..

TxGreaseMonkey · May 23, 2012, 09:48 AM

The bottom radiator hose leads right to the thermostat, which is on the back side of the engine.