Dan:

My 1990 745 has the same set-up.

DO NOT disable/remove either cooling fan. Each serves it's own purpose.

Sooner or later, they both will fail, for different reasons - hopefully not simultaneously.

An inoperative electric fan can be caused by any of several conditions:

1) fan itself is burned out. You have eliminated this by powering directly.

2) thermo switch on side of radiator, passenger side not working.

This is not easy to check. I just went ahead and replaced mine, figuring that it was 10 years old. Note: ALWAYS replace the rubber grommet

into which the thermo-switch is seated. NEVER try to re-use the grommet.

Lube grommet with Vaseline inside and out before installing it.

3) Relay is bad. Mine was. It is the outboard one of 2 identical relays

mounted on the front side of the passenger side strut tower. You can test this theory by switching it with the inboard one, then jumping across the thermo-switch contacts with ignition ON. If fan runs then, replace relay

4) Coolant just isn't hot enough to trigger fan operation. This could be possible during the winter: however, mine still comes on, even in November, during prolonged periods of idling (ie, stuck in traffic, waiting in line at toll booth after high-speed run, etc.).

Volvo didn't put both fans on these cars without good reason. Get them both in order (by the way, the viscous clutch driving the engine-mounted fan will fail sooner or later as well....).

George in PA

The electric fan has a thermostat as a switch at top right side of the radiator. It will only turn on when the coolant is really hot but not hot enough to cause damage to the engine.

The fan running from the engine is more reliable than an electric fan. Electric fan after time has intermittent contact problem or the motor jams. With the engine fan it will always work unless both belt broke. Note that Mercedes and BMW maintain the engine fan design rather than using electric fan like Japanese cars.

To test the fan whether it is working from time to time just disconnect the

2 terminals at the thermostat and make contact between them. You should see the fan turning. If it doesn't something is wrong with the wiring.

My 89 740 has the same set-up..the fan behind the rad is the regular one,the electric one in front only comes on when the car is about to overheat...DO NOT disable this one. It will save your car's aluminum head from heat warping. The temp sensor for overheating is located on the top passenger's side of the radiator. Get yourself a Hayne's Volvo manual (or equivalent) and also read the FAQ section of this brickbard covering the 700 series and save yourself a lot of money and grief. Hasta luego,Genaro.