Run away cooling fan

Southern Comfort · #1 10-12-2008, 09:27 AM

Has any one ever heard of a cooling fan running without the engine running at all. It comes on and runs the battery down. I have change the relay because the contacts were burnt, I'm also going to change the temp sensor today. Any and all help is appreciated.1995 Honda accord ex 2.2L vortec engine

Thanks,
SC

mpumas · #2 10-13-2008, 02:54 AM

The fan will sometimes run when the engine is not running but it should stop after a few minutes. If it continues to run the relay maybe sticking or you may have a bad temp sensor. The temp sensor is a switch so if it continues to run when you think it shouldn't, disconnect the wires to the sensor. If it stops, it is the sensor.

Shrewz92 · #3 10-15-2008, 12:45 PM

Quote:

Originally Posted by mpumas

The fan will sometimes run when the engine is not running but it should stop after a few minutes. If it continues to run the relay maybe sticking or you may have a bad temp sensor. The temp sensor is a switch so if it continues to run when you think it shouldn't, disconnect the wires to the sensor. If it stops, it is the sensor.

mpumas, where is/are the temp sensor located on 1991 Accord? I see a sensor/switch in the thermostat housing area, and there looks to be a sensor/switch under the distributor. I'm having radiator cooling fan start up much later than immediately AFTER engine shut-down, and catching my spouse with a dead battery mornings after she works. I've pulled a cooling fan 20a relay/switch in the engine-bay fuse-box to stop the A/C cooling fan (passenger side of engine) and pulled the 15a cooling fan fuse in the same engine-bay fuse-box to stop the radiator cooling fan from running.

mpumas · #4 10-15-2008, 03:14 PM

The one on the thermostat housing is switch A and is for the cooling fan which I think is the one you may be having problems with. The other switch is switch B and is for the airconditioning fan. I think that one is on the left bottom side of the radiator.

Shrewz92 · #5 10-16-2008, 03:06 PM

mpumas, thanks for the locations for the temp sensors. I ran Accord about 15 mins last night. Both fans came on. AC was NOT on. I pulled off the Switch A connector, as was suggested, and neither fan stopped running. I put the connector back on, then pulled the large relay in the engine-bay fuse-box labeled 'Cooling Fan.' That one stopped BOTH fans. I put it back in and they turned back on for about 15 secs, then they stopped. I couldn't get just ONE of the fans to run singly. This suggests to me that the relay is in poor condition/stuck on/down-right broken. Am I correct in that belief?

mpumas · #6 10-16-2008, 07:19 PM

I re-checked the drawings and switch B is located on the upper hose housing where the hose that comes from the radiator connects to the engine. They all input into the coooling fan timing unit. . Switch A should close at 184F and switch B should close at 226F. So if switch B is shorted or closed at a temp lower then 226F or the temp is above 226F, it would cause both fans to run. I would pull the switch B plug and see what happens. You can also pull the sensor and temperature test it. Or check the wiring. The blu (switch A) and/or wht/grn (switch B) may be shorted to ground. If the temp switches and wiring are good, then the problem may be with the cooling timer unit.

Shrewz92 · #7 10-17-2008, 08:50 AM

Quote:

Originally Posted by mpumas

I re-checked the drawings and switch B is located on the upper hose housing where the hose that comes from the radiator connects to the engine. They all input into the coooling fan timing unit. . Switch A should close at 184F and switch B should close at 226F. So if switch B is shorted or closed at a temp lower then 226F or the temp is above 226F, it would cause both fans to run. I would pull the switch B plug and see what happens. You can also pull the sensor and temperature test it. Or check the wiring. The blu (switch A) and/or wht/grn (switch B) may be shorted to ground. If the temp switches and wiring are good, then the problem may be with the cooling timer unit.

Thanks. So, to understand locations correctly: Switch A would be down low on radiator bottom, switch B would be up top close to the thermostat. Where'll I find that cooling fan timing unit? Is it in an accessible location? I'm not familiar with what it looks like, nor where it is. Two nights ago, after the suggestion of pulling the plugs, I pulled the plug on the switch B, but the fans continued to run. I didn't know location of Switch A. I've not taken a multi-tester to the wiring nor the switches. Would simple continuity tester work on testing the circuitry?

mpumas · #8 10-18-2008, 12:17 AM

No both switches are on the engine near where the radiators hoses attach to the block. The thermostat housing is near the distributor and has switch A. This is the discharge point from the engine to the radiator. (This is just opposite from any other car I have worked on.) The inlet to the engine is from the top of the radiator and has switch B there. The radiator fan timing control unit is in the passenger compartment drivers side up under the dash above the internal fuse box. and next to the main relay.

Shrewz92 · #9 10-20-2008, 08:57 AM

I'm working on a '91 F22A4 engine. I"ve only one hose from engine to radiator, up top. That one is the hose from the Thermostat to radiator, which dumps in just to the right of the fill-neck, as I'm looking from front of engine bay to firewall. That's switch A, as I understand your last post. Thank you for that description. Switch B would be down low on the engine block, somewhere close to the heater hoses? Thank you for the location of the fan timing control unit.

mpumas · #10 10-20-2008, 09:16 PM

I think just the opposite. That is switch B. The thermostat is located near the distributor. That is also where the bleed valve is located. The hose that goes to the top of the radiator is the inlet to the engine. It is just the opposite of every other engine I have ever worked on. So switch A is near the distributor and switch B is on the hose fitting near the top center of the engine and goes to the top of the radiator.

Shrewz92 · #11 10-21-2008, 08:17 AM

Thank you for that description. I saw under the distributor 2 sensor-looking/switch-type things. I wasn't sure if one of them was a temp sensor for the engine. One is a larger diameter, to the lower left of distributor: that one is one of the two temp sensors, as I understand your posts; one is smaller diameter (oil pressure switch?). Both are/were oil covered, unfortunately. I tried wiping them free of the oil about 5 weeks ago, and that's when this run-on stuff started. I bet an oil-deteriored insulation-wrap started this. Thanks again, for your assist.

mpumas · #12 10-22-2008, 08:42 PM

Oil pressure switch is on the back of the engine above the oil filter. You best bet is to use water based degreaser tand water to clean the oil off the engine. If you don't know which sensor/switch, look for wire colors, that will id the sensor/switch.

jeffcoslacker · #13 10-26-2008, 08:24 AM

My friend's '89 had this problem, followed by a host of other electrical demons...

Deteriorated wiring insulation allowing power from one circuit to power another was the culprit...harnesses along the front of engine and core support were both bad and had numerous places for voltage/ground trading between circuits...seems to be becoming a common problem as these vehicles age.

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