Whenever the auxiliary electric fan switches on, the engine idle drops then quickly recovers. Other posts that I've read indicate that this is caused by an increased load on the alternator. Is there a way to reduce this reduced idle effect, or what areas/connections should I be looking at that may contribute to the problem? Thanks!!

I've just replaced the original electric fan with a 16" SPAL, and the difference is very noticeable. Little to no rpm drop when it starts up with about the same noise level. Thanks, guys!!

Just out of curiousity, when does yours come on? There's been some recent postings suggesting they only come on under extreme conditions. DO you notice your temperature gauge rising before it comes on?
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Paul NW Indiana '89 740 Turbo 103,000

When we purchased out '90 744T, the fan was siezed, the temperature gauge never went over center scale. I later found that the thermostat was doctored to stay open, someone had pulled the plunger back and twisted it. A year later, I installed a new fan.

From the driver's seat, I never notice it come on, but in my yard, I can hear it running if I really pay attention.

It runs once and a while in the summer after I shut the car off. If I start the car in mild weather and let it idle, the fan will start after 15 minutes or so.

Since we installed the new thermostst, the temperatuer gauge never goes over center scale.
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3 8s & 2 7s 740,000 miles total

The temp gauge doesn't move a bit from 12 0'clock, although I do have a three row radiator installed. The temp switch mounted in the radiator (apparently not OEM) is set to turn the fan on at 92 degrees and off at 82 degrees (C). I typically drive to and from work with a 6 mi freeway stretch between the slower surface streets. After leaving the freeway (65-75 mph), the fan won't come on until I've let the engine idle a few minutes in the parking lot/driveway, after a 1 to 2 mile drive on city streets. So far we've had ambient temps in the high 80's (F). I've read that the Volvo dash temp gauges are "compensated" to remain in the upright position over a range of temperatures, and I realy should insert a probe into the coolant stream to get a better idea of the temps that are being generated, but so far no problem has been indicated by the dash gauge.

You could get a more powerful or newer battery and the system wouldn't undergo such a drop when the fan is first started. The alternator should still be able to handle it, but it might be more likely either that the fan is taking a lot of power to start (old, worn fan, partially seized, etc.)
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Chris Herbst, near Chicago.

Ted,

I've never noticed a voltage dip when mine turns on. Actually, though, I'm never really aware when it turns on. It's not noticable to me. I did jumper the thermal switch on mine to make sure it worked and the temperature gauge never gets above dead center so I assume all is well with it.

The current inrush upon start up to the motor causes the voltage dip. It sounds like yours is having trouble getting to speed, as chris suggested.
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Paul NW Indiana '89 740 Turbo 103,000

Ted,
As with any electrical device especially with motors, when they are first turned on there is a significant amperage draw. This is due to the lack of counter-voltage and the lack of inertia with the fan. Mine does the same, i am not sure how many amps the fan draws at operating level but I bet its over 5 since it has its own relay. The result is a strain on the alternator, if you think you have real problems..do check the wiring, relay and physical condition of the fan.
peace