Cooling Fan Circuit Question

Haz331 · #1 (**permalink**) 09-05-2006, 07:47 AM

When I turn my cooling fan manually it comes on with no problem, but when I turn the switch off, it continues to run until I kill the battery power. Is this a case where I need to install a diode somewhere? Any help would be appreciated.

Power Surge · #2 (**permalink**) 09-05-2006, 09:48 AM

Do you happen to have a thermostatic control somewhere maybe? I have a customers ERA here and it has a manual switch and one day it stayed running after I shut it off and I thought there was a problem but it turned out to also have a therm setup.

undy · #3 (**permalink**) 09-05-2006, 10:03 AM

It sounds like once you manually turn it on you're powering the control side of your fan relay. When you "manually" turn it back off the line side of the relay's still back feeding the control side. Not knowing your schematic, I'd imagine a diode could be installed so as the eliminate the back-feeding. A simple rewire would possibly work too.

Dave

jarendall · #4 (**permalink**) 09-05-2006, 02:03 PM

have you tried turning the thermostat all the way in each direction to see if it will shut down, you may be pulling enough hot air across the temp probe to cause the thermostat to engage, if this is the case, you may want to rewire the fan to a switched power source, so that the fan will shut off when you turn the ignition off

ebustin · #5 (**permalink**) 09-05-2006, 05:19 PM

Sounds like you do have a thermostat to controll your fan. See if you have two thermostats (water)on your motor. An other proplem may be the relay is bad ,If when you turn the ing on sw. off and the fan comes on. Good luck

Haz331 · #6 (**permalink**) 09-06-2006, 06:40 AM

Thanks guys, the question comes to mind, if the fan is not running prior to turning on the switch, why would it run after turning the switch off? (I'm talking about just flipping the switch on-off). If the temp. was not high enough to trip the sender, then it should not complete the circuit when switched off. Right?

Power Surge · #7 (**permalink**) 09-06-2006, 07:35 AM

Quote:

Originally Posted by Haz331

Thanks guys, the question comes to mind, if the fan is not running prior to turning on the switch, why would it run after turning the switch off? (I'm talking about just flipping the switch on-off). If the temp. was not high enough to trip the sender, then it should not complete the circuit when switched off. Right?

On the ERA I have here, the therm overrides the switch. Try letting it go for a few minutes and see if it shuts itself off. It took like 4 minutes for this ERA fan to shut off after the car was off, when it was hot.

trularin · #8 (**permalink**) 09-06-2006, 07:43 AM

Well, that looks good on paper. Sounds like you have a feedback loop.

Did you or do you have a diagram of the circuit? The switch turns on the relay that has a #10 or better wire to and from the relay socket.

As a test, you could pull the realy and test the socket. Put either a test light or DVOM lead into each of the contacts and see what turns on and off as you toggle the switch. Make sure your meter ( if you are using one ) is on Volts.

The coil should show 12V with the switch on and the other side of the coil connected to a good ground. You can check your grounds with the Ohm meter. Anything higher than .3 Ohms should be suspect and may need grounding help.

So, turn on the switch and you get 12V. Next, unplug the fan ( if you can ) and put the relay in the circuit. Now put your test lead to the controlled side of the relay to the fan. It should be 12V. Turn the switch off and watch the voltage. It should die to zero.

This should help you figure out what is going on, I hope it helps enough to fix the problem.