radiator fan issue
Thread Starter
AudiWorld Junior Member
Joined: Oct 2003
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radiator fan issue
Hi,
My 1987 5000TQ CS Wagon has been seeing intermittent, but severe over heating
problems. It appears the radiator fan
is not coming on when it should. It does
come *after* I turn the car off if the engine
is warm, but often is not on even as the temp gauge passes the midway point while the engine is running.
Short of replacing the radiator fan controller/resistor and/or radiator fan relay
is there a way to override them so the fan stays on while the engine is running?
Also any tips for testing the relay and controller to see where the issue is coming from?
Any help is greatly appreciated.
Thanks,
Bill
My 1987 5000TQ CS Wagon has been seeing intermittent, but severe over heating
problems. It appears the radiator fan
is not coming on when it should. It does
come *after* I turn the car off if the engine
is warm, but often is not on even as the temp gauge passes the midway point while the engine is running.
Short of replacing the radiator fan controller/resistor and/or radiator fan relay
is there a way to override them so the fan stays on while the engine is running?
Also any tips for testing the relay and controller to see where the issue is coming from?
Any help is greatly appreciated.
Thanks,
Bill
AudiWorld Member
Joined: Jun 2008
Posts: 455
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easiest way is to hardwire the fan right from b+ to a relay then to switch BUT...
before rewiring anything, make sure the fan motor has a good ground. its exposed to the elements and can easily get corroded and rusted and grow GFS (Green Fuzzy Stuff) or in some cases Blue Fuzzy Stuff... if there is an absence of fuzzy stuff and if youre familiar with how a basic relay works, this is a very easy wiring job. 12V to the relay and ground it with a a switch. power out of the relay to the B+ on the fan motor, and you can use the existing ground to complete the circuit. good luck!!
if you can find a relay that has the same pin configuration as the fan relay, try swapping them and see if it works. the coil can be tested by holding a 9v battery up to the two coil terminals on the relay. if it clicks, the coil is in good shape. if not, junk relay.
if you can find a relay that has the same pin configuration as the fan relay, try swapping them and see if it works. the coil can be tested by holding a 9v battery up to the two coil terminals on the relay. if it clicks, the coil is in good shape. if not, junk relay.
AudiWorld Member
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Re: radiator fan issue
if fan runs with key off resistor is ok.could be switch in raditor or stuck thermostat.check and see if radiator is getting hot at lower hose,if so thermostat ok.pull plug off rad swith jump blue/red wire to other wires one at a time, fan should run on med and high speeds if wiring and relays ok
AudiWorld Member
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From: Zinzinnati, Ohio
Check Radiator Fan Temp Sensor located at lower left of rad fan.....
Temp sensor may be corroded, or just burnt out. Check wiring at plug also. I believe its a 2 prong plug, and sensor unscrews from radiator. If temp is ok while driving, but rises while at a stop light, this sensor may be the problem. Can find this at rockauto.com for about 18 bucks.
Thread Starter
AudiWorld Junior Member
Joined: Oct 2003
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Re: radiator fan issue
Thank you very much for all the responses. I was
able to get the fan to run by turning on the the
heater and/or AC (duh!.... I did know that, but didn't think of it). The car still overheats very
quickly.... So I'm thinking water pump? I've replaced the auxiliary turbo pump a while back.
One other question: do the same temp sensors turn the fan on when the car is running and when the car is off? IOW, why do the sensors know the car is hot *after* it's shut down, but not while it's running?
Thanks again
able to get the fan to run by turning on the the
heater and/or AC (duh!.... I did know that, but didn't think of it). The car still overheats very
quickly.... So I'm thinking water pump? I've replaced the auxiliary turbo pump a while back.
One other question: do the same temp sensors turn the fan on when the car is running and when the car is off? IOW, why do the sensors know the car is hot *after* it's shut down, but not while it's running?
Thanks again
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theres gotta be 4 different sensors for temp
but I really forget which does what.two single pole ones near the water outlet: one gives the isv a signal i know that for a fact. but there is a 3/4 pronged one in the same area, and one on the side of the rad.
the afterrun pump is controlled by a relay connected to one of these sensors.
if the car overheats very quickly, I'd look into a possible stuck thermostat before starting to rip everything apart on the front end.
check out this site for more info on the various temp sensors<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/cooling.html">http://www.sjmautotechnik.com/trouble_shooting/cooling.html</a</li></ul>
the afterrun pump is controlled by a relay connected to one of these sensors.
if the car overheats very quickly, I'd look into a possible stuck thermostat before starting to rip everything apart on the front end.
check out this site for more info on the various temp sensors<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/cooling.html">http://www.sjmautotechnik.com/trouble_shooting/cooling.html</a</li></ul>
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Thread Starter
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Re: theres gotta be 4 different sensors for temp
I think you are right:
"if the car overheats very quickly, I'd look into a possible stuck thermostat before starting to rip everything apart on the front end."
The article you suggested:
"If the Thermostat doesn't open completely, there won't be enough water flow through the radiator which can cause overheating, and there may not be enough hot water flowing to allow the radiator fan switch at the bottom of the radiator, to heat up and turn on the radiator fan."
I have both symptoms (no fan and quick overheating). It overheats even if I over-ride
the fan to on. Moreover the fan is coming on fine
*after* the car is turned off.
Anyway, it seems like the most logical starting point. I'll post my results.
Thank you!
"if the car overheats very quickly, I'd look into a possible stuck thermostat before starting to rip everything apart on the front end."
The article you suggested:
"If the Thermostat doesn't open completely, there won't be enough water flow through the radiator which can cause overheating, and there may not be enough hot water flowing to allow the radiator fan switch at the bottom of the radiator, to heat up and turn on the radiator fan."
I have both symptoms (no fan and quick overheating). It overheats even if I over-ride
the fan to on. Moreover the fan is coming on fine
*after* the car is turned off.
Anyway, it seems like the most logical starting point. I'll post my results.
Thank you!
Thread Starter
AudiWorld Junior Member
Joined: Oct 2003
Posts: 44
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Re: theres gotta be 4 different sensors for temp
Thanks again for the info. I ended up replacing
both the thermostat and the fan switch. I think
the thermostat had been somewhat problematic for
some time and the car is running cooler in general
now.
Thanks again.
Bill
both the thermostat and the fan switch. I think
the thermostat had been somewhat problematic for
some time and the car is running cooler in general
now.
Thanks again.
Bill
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