Electrical radiator cooling fans

[ralley]

Folks:

The Zeppelin is fitted with a gang of 2 electrically driven cooling fans forward of the radiator. I presume that there is an adjustable rheostat to cause them to come on/off somewhere. Any idea where?

[overlander63]

If it's newer than about a 1990, it may be controlled by a sensor and the ECM. The sensor is a small device that usually is threaded into the intake manifold with 2 wires going to it. Is the engine fuel injected or carbureted? Are you having problems with the engine running hot?

[TomW]

Originally Posted by ralley

... I presume that there is an adjustable rheostat to cause them to come on/off somewhere. Any idea where?

In the late eighties, GM big-block, electrically-driven, raditor fan motors were turned on by a coolant-sensing, thermostatic switch mounted on the passenger-side head.

The switch costs $89.34 around here and is not adjustable.

Tom

[ralley]

Thanks, all--I'll run a test to see if the fans are working. It was running a bit hot, but not consistently, last week, when the ambient temp was about 80F. I'd guess either the thermostat was opening late, or the aux fans were not working properly.

If the switch is coolant sensed--at what temp is the switch closed, making a circuit? Are there different temp switches available, like thermostats?

Best,

R

[TomW]

Originally Posted by ralley

... --at what temp is the switch closed, making a circuit? Are there different temp switches available, like thermostats? ...

Maybe.

IIRC, the switch closes at 220 degF. The one GM was using (P/N 2064526) is available as TS-239 at parts houses. You might want to ask your regular auto parts man that question.

Don't forget that you can wire a mechanical switch, mounted to your dash, in parallel with the temperature switch.

Tom

[ralley]

Originally Posted by TomW

Maybe.

IIRC, the switch closes at 220 degF. The one GM was using (P/N 2064526) is available as TS-239 at parts houses. You might want to ask your regular auto parts man that question.

Don't forget that you can wire a mechanical switch, mounted to your dash, in parallel with the temperature switch.

Tom

Thanks very much--engine temp on the road begins to drop at about 220F--so they might be working, but which I think a little high. I like the dash switch idea if I cannot get a lower closing thermal switch, say, at 200F.

Best,

R

[TomW]

Originally Posted by ralley

Thanks very much--engine temp on the road begins to drop at ...

You're welcome.

Keep in mind, though, that fans, whether electrical or mechanical, are only useful at vehicle speeds below about 35 mph. Above that the fans' contribution to cooling is negligable.

Tom

[ralley]

Got it, thanks--there are a lot of people in the Washington-Baltimore area, and there are times when 35 MPH on the interstates is positively fast. Two weeks ago, it took us 5 hours to get to Carlisle, PA, most of it at a slow roll in the ring roads getting around DC and Baltimore. From where we live, it's only 160 miles. Hence, the concern about heat. My test yesterday has convinced me that all is working properly, even though the thermostat may be opering late--it is opening. It may be due to lack of use over the winter--Zepelin had been parked since Christmas.

Best,

R