Hi all.
92 740, non turbo , regina w/ 115k miles.
I am a noob with volvos. This is the first I have owned.
I noticed my fan seems to turn on and off a lot. Once the engine is at running temperature (Seems like it gets to running temp real fast too) the fan turns on at every stop light and anytime I shut the car off.
Does this sound normal? The air temp isn't very hot. It's like between 60 and 70 degrees out. The engine temp gauge never goes over halfway and I have no signs the car is running hot.


Any thoughts?

UPDATE!!!!

Since I have a broken arm I took to local Volvo mechanic. He found a code and replaced the ( Im not sure if this is the right term) Water temp sensor.
He said it was behind the manifold and connects in the block.

Anyways it fixed the problem . So nice to not have the fan constantly turning on!!!

Thanks everyone for your help.

I still have a problem with the car shuttering at idle when warm but I will start a new thread about that.

Update: asked my mechanic when I took in for an oil change the other day. He also seemed to think it was the radiator cooling fan switch.

Is that something I can change by myself? I broke my arm so it would be one handed. It doesnt look like it is threaded in. Maybe just pushed in with a rubber grommet. Is it that easy. Take electrical connections off, pop out, put new one in and reconnect to electrical connections?

Yes, it's about that easy. But get a new rubber grommet along with the switch.

See here: https://www.brickboard.com/FAQ/700-900/Cooling.htm#RadiatorSensorSeal

Consider getting one of those little infrared temperature sensors, such as this one:

http://www.harborfreight.com/infrared-thermometer-93984.html

They are relatively cheap and can tell you if you really have a temperature problem. And they have plenty more uses than around cars.
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Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), and 2010 XC60. Also '77 MGB and some old motorcycles

I've never seen my 740 temp gauge get above the middle in 17 years except when the water pump seized. Whatever the design, it is pretty sticky in the middle.

The thermostat is cheap, easy to replace, and a wear item that should be replaced so go ahead and do that anyway.

The radiator surface could be dirty making it inefficient. Cleaning it with a condenser coil cleaner or just even a hose could help.
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Paul NW Indiana '89 744 Turbo 180K/ '90 745 turbo 145K

IIRC, the Regina FI system cars use a thermal switch in the radiator right side tank to trigger the fan. Bosch LH 2.4 triggered the fan from the ECU, and had no rad switch. I had a 940 and the fan only started up when the engine got quite hot, or the A/C was cycling.

So, I see three possibilities:

- the engine is indeed running hot, so replace thermostat and see if that does it

- the fan switch in the rad is triggering at too low a temp - replace it

- the A/C pressure monitoring (pressostat) is triggering the fan too soon. Hope that isn't the case, as they are a pain to swap out. (If you are not using A/C when your fan issue occurs the pressostat is not the problem.)

As for 740 temperature gauges, the one I have in my parts bin has a rather sophisticated looking printed circuit board on the back side, with several transistors, diodes, resistors and capacitors and an 8-pin integrated circuit. More than is needed to simply provide a smooth gauge response to the sender as the engine temperature varies.

I once attached an ohmmeter to the output terminals of the gauge temp sender on the engine of my 940 and it was interesting to see the resistance drop quickly as the engine warmed up, stabilize as I cruised down the highway, then drop further at a stoplight. With everything connected back up, I never saw the gauge move once warmed up, so I conclude that there is some damping going on in the "normal" range of engine temperatures, just like the later 240's.

The temp gauge on my S90 (rebadged 960) is driven from the ECU, but I believe all 700's/940's used a separate sender on the engine. Certainly my 1994 940 did.
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Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90, and XC60. Also '77 MGB and some old motorcycles

"I never saw the gauge move once warmed up, so I conclude that there is some damping going on in the "normal" range of engine temperatures, just like the later 240's."

My 1993 940 acts very, very different. Although I will admit it has a lot of on-center tendencies, it varies 1-2 needle widths either way of center almost constantly until I am cruising on the highway for more than 10 minutes. The second I pull off and come to a stop it climbs 1-2 needle widths and then drops back to on-center'ish.

In normal summer stop-and-go that is Chicago traffic it uses about 75-80% of the sweep on that gauge and the electric fan only kicks in (AC not on) when it is getting pretty close to the red zone. This is with all new radiator, hoses, heater hoses, etc. Have not replaced the water pump yet nor the coolant temp sensor.

Thanks for the reply.
My temp gauge stays perfectly centered. Did your 940 with the bad Tstat stay centered?
When you changed it the fan stopped coming on all the time? Thanks

Don't go by the temperature gauge. Its reading is fake, basically an analog "idiot light" that shows cool, medium and hot. I don't know why Volvo did that, other than believing owners might be unduly alarmed if they actually saw the temperature fluctuating. I had a 1989 Ford Tempo that I could tell when the thermostat was opening and closing by how the needle moved. I loved it.
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1992 745, >500k km

I am 99% sure you are mistaken. The 7/9 series does not have a temp faker board and the feed comes from the coolant temperature sensor and not the ECU.

The sensor itself being out of whack is not uncommon, though.

"The 7/9 series does not have a temp faker board"

All I know is that the temperature comes up and stays in the middle of the gauge all the time. With a "real" temperature gauge, I ought to be able to see the needle fluctuate as the thermostat opens and closes and the fan turns on and off.
--
1992 745, >500k km

Thanks for the reply.
My temp gauge stays perfectly centered. Did your 940 with the bad Tstat stay centered?
When you changed it the fan stopped coming on all the time? Thanks

Its a quick and easy job to change, I put the new one and the old one in a pot of water and boiled them and the old one wasn't opening fully. My gauge was fine so i never thought it was the thermostat, i stuffed around with the fan relay, a/c sensors, temperature sender switches, the computer and wiring to no avail.

Change the engine thermostat,went through this with my 940 and it drove me mad.