Radiator Fan Questions

[jdbs3]

1990 Vanagon GL

Getting my van ready for a road trip after its being in the garage over the winter. A few questions on the radiator fan:

1. If I am waiting for a period of time at a traffic light (e.g. stop and go in a big city) sometimes the radiator fan will come on; ditto if I leave the van idling for a few minutes.

Is there any rule of thumb as to how soon the fan will start? Does it matter how long it runs till it goes off?

Probably a stupid comment, but I have always felt it best to avoid having the fan run as much as possible.

2. Radiator fan and A/C

I've been reading everything I can on A/C; would like to use it on the trip. The radiator fan should go on as soon as I turn on the A/C switch, but it isn't.

What is the best way to diagnose this problem - where to start, etc. Yes, I'll check the fuses first.

thanks

[shenan-agon]

1. Sounds like normal behavior to me - you should expect the fan to cycle on/off while idling or running at low speed when there isn't much airflow over the radiator. This GoWesty article explains the cooling system operation pretty well:
http://www.gowesty.com/library_article.php?id=52

2. Not sure on this one - my fan turns on when I flip on the A/C (even though I don't have functioning A/C anymore). I don't remember if it jumps right to the high speed or if it does low speed first - do you know if both speeds on your fan are working? Have you ever heard the high speed kick in? (You can test both fan speeds by jumping each pair of pins at the fan switch connector on the radiator). If I remember right, the wiring diagram doesn't show any interaction between the A/C and the radiator fan, even though we all know by experience that there is - might make it trickier to troubleshoot...

[crazyvwvanman]

Vanagon Bentley page 97.145 shows the 1989+ A/C wiring connections to the radiator fan circuit.

The fan should come on at the lowest of 3 speeds when you switch on the A/C. If it doesn't, the common problem is the fan resistor for low and medium speed. The resistor burns out and then one or both lower speeds stop working. It lives behind the driver side headlight, as shown on page 87.5 in the A/C section.

Mark

[Wildthings]

You want the fan to come on fairly quickly when you slow down on a hot day, otherwise you will heat soak your engine. If you install a new fan switch with a -75 suffix on the part number it will come one earlier and cycle more frequently while keeping the engine temps very constant. In my experience the fan will even last longer is if is cycled more frequently, maybe spinning it more often helps the bearings and the shorter cycles keep the resisters and winding from getting as hot. Don't know for sure.

[GWTWTLW]

From what I've heard others here say, if the 3rd speed fan comes on at a lower temp, it will shut your AC off sooner as well.
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[crazyvwvanman]

True, with 86+ the A/C compressor is shut off by the high speed fan switch. Using the 75 degree switch will diminish the A/C cooling on hot days.

I have tried the 75C switch twice on different vans and took it back out both times. Not because of the A/C but because it ran the fan way too much.

Mark

[mtnwater]

My radiator fan only comes on when my AC compressor is engaged - i.e. there are times when my AC is on and my radiator fan isn't. As soon as the compressor clutch kicks in, the fan comes on. Is this correct operation, or should my radiator fan be on continuously when the AC is on regardless of the compressor state?

[Wildthings]

[GWTWTLW]

I believe it is tied to the compressor.
_________________
89 Syncro Westy - GW 2.5, now with a double knob job
@gwtwtlw

[tencentlife]

Could be the low speed is inop because of bad series resistor. The 2nd speed is only activated by the AC high-side pressure switch, so maybe the pressure gets higher faster because the low-speed fan isn't working; it would help lower hi-side pressure by condensing more gas.
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[mtnwater]

Thanks for the reply tencent - I appreciate the feedback. The resistor and fan thermo switch are both relatively new (w/in the last 10k miles). I thought the fan was only two speed? I can get the fan to blow both high and low by jumping the wires on the fan switch, so assumed all was well with the resistor. Fan seems to kick on when the coolant temp climbs, so I believe the thermo switch is working okay too.

As for fan operation with AC, I confirmed this afternoon that the fan only comes on when the compressor is engaged - the compressor and the fan both kick on at the same time. If the AC is on but the compressor isn't engaged...no fan. Any thoughts as to what's up? SEems okay to me, but if something is wrong I'd like to fix it. For reference, my van is a '90 syncro.

[Penny Wolin]

I just acquired a 1989 Vanagon Westfalia with 43K original miles. The radiator fan runs all of the time, and turns off when the engine is turned off. My local mechanic who just bled the system said,"Great, let it run." I don't think it is meant to run all of the time, is it? What is going on here? Thank you.

[jdbs3]

RE: Are you sure it isn't coming on when you first turn the switch and you just aren't hearing it? On low the fans doesn't make much noise. The fan on low is much more audible when standing in front of the van than sitting inside.

It works; comes on immediately. Standing in front of the van helped.

Thanks all for the feedback. Now on to replacing the R12 with Red Tek.

[dannywk]

I also have the problem of the fan running constantly. This is a bigger problem in the winter when i would really like the van to warm up.
If anyone had this problem and fixed it, i would love to hear how you did it.