How to test 1984 Vanagon radiator temp sensor?

[drawlusyk]

Hello all. After days of reading posts I still require some assistance.

Twice in the past 2 weeks coolant has boiled over when parked idling.

I would like to test the fan coming on when rad gets hot. Not sure how.

Background:
-when coolant reservoir is empty blinking dash light comes on so tells me that sensor is ok.
-dash gauge goes up when temp increases so gauge works
-rad gets warm when engine running
-unplug sensor on front of rad and short out resulting in both high and low fan speeds
-can drive without over heating. temp gauge sits at 1/2 just over the light

not sure if I have ever heard the fan kick in automatically

I am now wondering if there is a way to test the sensors that automatically starts the fan when rad gets hot? Any ideas?

Regards
Dennis

[Zeitgeist 13]

Just buy a new fan switch--it's a switch, not a sensor. The only way I know to "test" these switches, is to remove them and place them in boiling water with a temperature probe and multimeter to see at what temps they switch between poles. They act like a single pole double throw toggle switch
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Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[drawlusyk]

Ok great thanks. I have just ordered a new one and will test that way.

[atomatom]

you can also buy an IR thermometer that you can point at things on your van to see how hot they are. this along with the magnet on a stick, a 11 & 13mm wrench/socket are my favourite van tools.

there are two versions of the fan switch, the later year one is the recommended alternative for your van. early models like yours (and mine) originally had the fan kick in at a higher temp. later on, it kicks in at a lower temp. (i cant recall the exact temp)
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84 Vanagon Westy, 1.9L, California raised but defected to Canada.

[SubArcticHank]

I'm troubleshooting the same issue, however I have found that my fan does come on at a very high temperature. This may be due to a bad switch or because I have the wrong (high temp) thermostat. Since I have air conditioning I have been able to turn on the AC blower which automatically turns on the low speed fan, so changing the switch isn't so urgent. Anyhow, the thermostat is also a possibility so I hear. 84 1.9 westy

[RicoS]

[RicoS]

[Terry Kay]

Richie Wrote;

<<In order to preclude any confusion or uncertainty, the Radiator Fan Switch in a Vanagon consists of two single pole, SINGLE THROW switches, in parallel, with distinct set points in a common switch housing>>

Which will not switch on if the radiator is plugged up in the lower portion of the radiator.
Garbage in the radiator could very well be plugging the tubes and sheilding the switch from reading the correct temp and turning the fan on at it's programmed temp.
Very Common Problem.
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T.K.

[RicoS]

[RicoS]

[drawlusyk]

Still waiting on the themoswitch. BUT today for the first time saw a small leak on the driveway after a short drive. Looks like its also time to replace the radiator:(

[Wendy.the.Westy]

Is there a radiator replacement off-the-shelf option or modification that introduces a fill cap at the top of radiator? Seems like it would make sense to fill the system at its highest point......right?
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ID.BUZZ

[Terry Kay]

There ya go--nice project for you.
Modifying Vanagon radiators.

That picture of the radiator is real nice.

An original skanky radiator.
I'll bet the tubes are all plugged up on the bottom portion of that radiator, hence the fan switch not operating at the correct kick on temp.
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T.K.

[drawlusyk]

Well guess it was time for a replacement.
New one is in, but cant get the needle past the 1/2 mark to see if the fan kicks in!

[Mighty Van]

I know you are changing rad but just went through this today with same vintage VW but car not van.12 dollar rad cap. Would boil over when Guage hit the 3 thirds mark. All wires ect checked good so thought switch itself in rad must be toast. New cap and took it up hill. Popped hood at same mark on temp gauge to check with heat gun. Switch showed 195 and all of a sudden fan came on like it should. Then with the new pressure coolant hose to oil cooler blew! She's all good now though , had the tool box along.