i have a 90 accord lx when running fan dont come on so engine overheats.
fan works when engine is turned off(only passenger side), jumpered sensor unit on thromostat housing and fan works(only passenger side), replaced sender unit on termostat housing but fan still wont work while engine is running. also turned on ac and than fan comes on ( passenger side only).
what could be the problem. I was thinking of trying termostat replacement next but i dont see where that is fan related. i also checked all the fuses under the hood, all look good.

any ideas guys?

 

Unplug the electrical connector for the driver's side fan motor. Start the car and turn on the a/c. Check for 12V across the two pins of the electrical connector.

 

Thanks for replying PAHonda, I have not got that far into trouble shooting. I was trying to get passenger side working first. But I will try disconnect the driver side fan and check for power, I was assuming driver side fan was not affecting
The other fan to not work while engine is running, because the passenger side fan runs when ac is on and when engine is turned off, but it don't turn on when engine is running and getting hot, why.

 

Pax side fan should run if the coolant temp reaches 194F (closes the thermoswitch A). Frequently I've seen the cooling fans will not come on w/o driving the car to provide more heat input, particularly if air temps are cool (< 80F). If pax side fan comes on when thermoswitch A (thermostat housing) is jumpered, then thermoswitch A is not closing at other times.

Two possibilities for Driver's side fan; bad fan relay or bad fan motor. Checking for 12V at connector as PAHonda suggests will identify which is the case.

good luck

 

Just replaced thermoswith with another one from autozone and fan still not turning on after driving it until it got hot. I also removed the thermoswith and boiled some water until temp reached 200f than placed unit in it and metered it to see if it closed, it failed the test it did not close. Is that a valid test and could it be that two new units bad out of box. Also tested and metered original thermoswith and it showed a reading of 006 resistance and the new one from autozone had no readind.

 

BOTH fans should run when the ac is on, assume a working ac system.


Do a search, posts started by me in General Tech (started by is key or you will find all kinds of stuff ).....one of them will have something in the subjest line about cooling fans........it will explain the operation of the system. Once you understand the system, finding the issue should be easy

Here : https://www.hondaaccordforum.com/for...similar-44973/

 

Thanks guy for trying to help, what I have done so far, replaced the driver side fan motor was bad now works when ac is turned on. Fans still not coming on while engine is running and hot, so what I did was short the plug on thermostat switch so fans run all the time, it don't matter engine still overheats. What is the cause? Also bleed cooling system while engine off, heater on, and water flowed out nipple on thermostat housing.

 

Suspect air in the cooling system is preventing circulation. Add coolant and bleed air at bleeder valve behind distributor.

It could also be a bad thermostat if this has not been replaced.

good luck

 

Thank you for all the help. Replaced thermostat { got part from dealer}and no overheat issue. Girl friend is happy for it is her car, as you all know it had multiple problems, bad fan motor, thermostat, and I also found a bad bypass hose. Thermoswith is okay, the original one is back in. I don't know if autozone will give me a refund on the piece of s..t thermoswith that don't work. I know now that always get original Honda parts and pay the extra $$$.

Thank,

Chrisds