740 How often does your electric fan run?

Hey everyone, picking away at some more maintenance on this 1992 745 Turbo, and while letting the car warm up in the driveway, I noticed that the electric fan never began to run. Even after getting up to operating temp according to the cluster gauge.

The needle never went past the "middle", but with no previous experience with electric fans on a redblock, I thought it best to check with you guys to see how often they run, and if the vehicle idling with the hood up in 45 degree fahrenheit ambient air temp would even cause the system to cycle on.

The last time I was working on anything with an electric fan (I've had a Jeep for several years), I was back in Florida and even idling at rest, pretty much every fan would start to cycle once the vehicle warmed up.

And correct me if I'm wrong, but from what I've found the 92 Turbo cars' fan is controlled by the ECU? Not by a sensor in the rad?

I upped the thermostat temperature to a 188 fahrenheit unit from what the previous owner had in there, and I could point a finger at the low temp therm for a non cycling fan, but now, before I go scooting about town, I'm hoping one of you fine folks can help me out.

Thanks gang.

I am assuming that you are talking about the OEM pusher electric fan on the turbo and that like my old 1987 745T, it also has the viscous clutch mechanical fan? If so, then under idle conditions at 45 deg F I would say that it would never start. In fact, I don't ever recall hearing the electric fan run under hood up on the driveway idle conditions, even in the summer. It might run if the air conditioning was on and you were stuck in stop and go traffic on a really hot day.

142 guy said:

I am assuming that you are talking about the OEM pusher electric fan on the turbo and that like my old 1987 745T, it also has the viscous clutch mechanical fan? If so, then under idle conditions at 45 deg F I would say that it would never start. In fact, I don't ever recall hearing the electric fan run under hood up on the driveway idle conditions, even in the summer. It might run if the air conditioning was on and you were stuck in stop and go traffic on a really hot day.

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It's actually a puller fan, with no clutch fan. It's OEM Volvo, but I can't be certain it was on the car from the factory. The relays are where they should be however (behind the driver's headlamp), so I think the car was built like this from the factory...

Almost never with that range of outside temperature. Turn on your defroster and see if the fan cycles on. Or, the AC. As long as you hear it come on, everything is fine. The later set up has a huge radiator that disapates so much heat the fan almost never comes on when idling.

You can always short the thermostat in the top left (if standing in front of the car looking at the engine). That will at least tell you if the relay and fan work. Won't tell you if it turns on at the right temp though. In those temperatures, the only time mine kicks on is stop and go highway driving.

If your car has the OBD ports under the hood, you should also be able to run it through the test cycles (half speed, full speed) to make sure the fan and the relay itself is working.

That said for me the fan rarely runs even in Texas - although sometimes in the summer I’ll turn the car off, and then back to position II and the fan will run a while to cool off the engine. It should run even when the car is off completely for up to five minutes if it’s extra hot, but I haven’t seen that happen for me in a while.

Perfect, thanks everyone. That gives me enough confidence to just road test and see how it goes.

Appreciate the quick replies!

Never I took it out because it was noisy, sucked electrons and didn't keep my turbo properly cooled.