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Engine fan and air governor


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To start with we have had this Volvo with a red top Cummins for over eight years. the fan always came on when the temperature was about 226 degrees. So I would pull over and let it cool down when doing a big climb on a mountain.

Well we where going over a 9000 foot pass and the engine was warm. The DW was in the passenger seat and there was anther HDT behind us with more vehicles in the wagon train going up this pass. No passing lane and it decided to cut the rpms to 1500. The DW noticed it would sputter if trying to pass 1500 rpm. finally found a pull off. Let it cool down and continue at below 1500 rpm.

The other HDT never crossed real mountain passes before so there was some things discussed about his . Then snow started to fall which bugged me as now I could not see the scenery.

Then there was the DW in the other HDT.


Skip those comments



The next morning the truck would not build air but 10 lbs. pressure. So I installed a new air governor.

It now operates at a few pounds pressure higher at cut in and where it shuts off.

Now the fan comes on at a much cooler temperature as we did take highway 2 over the Butte Mt mountain instead of interstate 90. Very nice two lane road and is a truck route. Never did see another truck but the yellow HDT following us.



Safe Travels, Vern

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I wouldn't think that the 2 would be related. But, maybe the extra 'high' temp shook something loose in the temp sensor?? My fan, Volvo D12D, comes on in the 210 range and drops pretty quickly.


The 1500 RPM, guess here, ECM limiting the boost pressure? I've heard, Ford Diesel site, that when you get in those altitudes, the ECM 'limits' the speed and pressure to avoid overspeeding the turbo's so they don't self destruct. Although, this guy seems to say they don't have the problem. -http://www.dieselarmy.com/engine-tech/boosting-altitude-elevation-effects-turbochargers/-

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Vern, I'm not sure that the de-rating wasn't part of the near over-heat condition & altitude you experienced.

Now I do not have a N-14, so things could be different than on my little D-12, but my fan will engage at between 195* & 200*.

I'm quite fine with that temp.




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thats one of the reasons i have the Fan override switch installed in mine. can turn on the fan when i want it to avoid getting that warm before the

fan turns itself on.


bigger issue is why the fan is only turning on when its that warm... think i would also be looking at replacing the fan solenoid.


i gave the part number of the override switch to sibernut (aka Ron) and he has one in his truck... believe his is a a cummins (mines a Detroit)

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