Relay Question

[mcm9970]

I am not a mechanic and enjoy my full time job. I asked an apparent "dumb" question which has resulted in several long posts. To those whom are confused by contradictions stemming from my lack knowledge on these posts- I apologize.

I mainly learned that I need a new mechanic because of ME confusing the electric fan and the mechanical fan. My mechanic has not dove into this yet and he is working on it next week. He was apparently asking about the relay for the electric fan and I need to inform him that the electric fan is working properly.

There IS an issue with the mechanical clutch. There is a new thermostat and temp sensor installed as I decided to replace them last year. The clutch fan and entire cooling system worked properly last year. I know and identify the "roar" turning on and off and certain temperatures. Now it "roars" with no regard to the engine temp and there is an obvious and brief "cycle" now and then. This sounds as if roaring stops briefly. That cycle has no affect on the RMPs. The temps stay well below 200. I know that the thermostat is fine and not stuck open. There is adequate airflow to the motor.

[mcm9970]

And 92- I remember when you bought your RV and posted for the first time. How on EARTH do you have 460 posts ?!?!?! I have a suspicion .........

[92landyacht]

Originally Posted by mcm9970

And 92- I remember when you bought your RV and posted for the first time. How on EARTH do you have 460 posts ?!?!?! I have a suspicion .........

And what would that suspicion be?

[HowieE]

mcm9970

You comment that you replaced the clutch for the mechanical fan last year. If the problem started shortly after that I would have to restate my comment that the operating range on those clutches is from 160 to 180 degrees. If by chance you got one at the lower in of the range and it is the confined space of a motor home that may be the answer.

I had one on one of my trucks that would not come on till the coolant was over 220 degrees but have known other that had them to cycle frequently.

If you can find a electronic thermometer and place it behind the clutch fan in the air flow coming towards the engine you could see if the clutch is in fact responding to temperature. The air flow will fluctuate over a wider range than the coolant in the engine because the thermostat is controlling that, at 180 degrees, by dumping heat into the radiator and thus increasing the air temperature hitting the clutch.

[mcm9970]

Thank you, Howie. When I had the fan clutch changed last year- on a summertime trip (90 F +/-) the fan turned on when the temp got to 200 and turned off at 180 or so- it did this for around 600 +/-. After that- on a winter time trip (50 F +/-) it turned on and stayed on keeping the temps at 180 +/- - it did this for 500 +/-. On our latest spring time (80 F +/-) trip it stayed on for the most part and began cycling on and off with no change in temperature or engine RPM. Could the outdoor temperature affect this?

I checked the fan and the fan has resistance when you turn it with the engine off- so it doesn't seem to be locked up.

[HowieE]

Yes

I can't find the GM specs on the clutch that states the wide possible operating range right now. But if you got one made to the low end of the range that may be the problem.

This should help you understand what is happening.

Fan Clutch Diagnosis - Engine Cooling System