Radiator fan not working

Not sure if someone can help, so noticed the car was overheating when stuck in traffic and turns out the radiator fans aren’t working. Getting voltage reading at temp sensor, however no continuity at on the fuse. Fuse is not blown.. checked other fuses and turns out only half the fuses are showing continuity. Am I being thick or does it sound like my fuse box may be the culprit here? It’s an 83 GTI with a 1.8t.


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Well removing each fuse and checking it is the only true test. You can check them in circuit with a DVOM to ground with the key on in the run position.

On the AGC fuses there are two silver tabs at the top, Test each tab to ground for 12V.

Could be the fusebox as they are flaky if water has gotten in.

Inside.



See the corrosion on my spare at F1.  Cleaning with a soft brush and ox-off spray will get them back to shiny.
corrosion free.

Take good photos of the rear before you take any wires loose so you can put them back correctly.

IIRC the Fans on the 83 are controlled from the Radiator fan switch.

Battery-To Radiator Fan Switch- to Fan.
Since the Fan is isolated it has to have a good ground to frame and a good wire to the Radiator switch.

I would Run a wire from the B+ 12Vdc battery to the fan to validate that the fan is working then go from there.  I have had more issues with the Radiator Switch over the years than 1 dead fan that I had.
 

Thanks for the response, pulled all the fuses and they were all fine.

I have been dealing with water ingress, and the fuse box did get wet. As soon as I realised i unplugged it and thoroughly dried everything out and cleaned up as best as I could.

It’s a series 2 fuse box but guess the same method applies.


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Briano1234 before i dive into the fuse box, decided to bridge the connection for the temp switch and fans came on. Replaced with a genuine new temp switch today, ran the car and still no fans. It seems I actually do have continuity at the fuse box.. is there a relay for the fan also? 

The radiator fan thermo switch should be the same rating as your t-stat Think of them as a matched set.

Did you test the new switch in a pot of hot water to see if it worked I before putting it in I have got a bad one once upon a time, as well as a bad new to me from parts store t-stat.  I verify they work.  I have a infra-red point and shoot temp gun that I use to measure the temp of the water to see the t-stat pop-open at the rated temp.  Same for switches.  only I use my DVOM to see them Pop closed at the correct temp.

Also does your Water pump push water, there have been issues with water pumps that have the plastic impeller that can get cracked and doesn't spin on the shaft.

If you have an expansion tank, is there a constant stream of fluid out of the expansion tank hose at the top of the jug?

If you have a side fill Radiator leave the cap off to see flow in the radiator.

Have you flushed and back flushed your cooling system and the radiator?

If you jump your Radiator switch and the fans run, then that tells you that everything outside of the circuit switch works.  Only the Switch is bad. But then I have a simplistic approach to things electrical.

last but not least do you have a single speed fan or a two speed fan.  The Radiator switch is either 2 pole, or 3 pole, use a two pole switch for single speed fan and a 3 pole switch for a 2 speed fan. (2 speed fans were originally for a/c equipped.)

I will look for my 83 bentley, but it is American based IIRC.

As above short the wires at the switch end and the fan should run, if not there a problem downstream of the switch

I the past I've come across the switch appearing not to trigger the fan even when the rad is very hot.

Turns out although it appears the switch is screwed into the side of the rad in the water flow its actually in a small gallery that can get blocked with debris/rust/sludge so never feels the heat of the water

have a look see what the switch is screwed into

Thanks both, bridged both wires, fans turn on. Therefore I assume wiring is as it should be.

Constant stream of water in expansion tank, so there is a good flow of coolant circulating. No evidence of a rotten water pump and signs of it leaking either.

So the problem definitely seems to lie with the temperature switch. The coolant is has got some small particles of debris in it, although it’s less than 10 years old.

In order to inspect the where the switch plugs into I will need to drain the coolant really. So I guess a full coolant flush is probably in order. If this doesn’t solve the problem I will be pretty stumped on what to do. The switch appears to be in the factory location..

How do you test the switch itself to see if it’s functioning?


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Guy94 said

How do you test the switch itself to see if it’s functioning?


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RMFA.

Did you test the new switch in a pot of hot water to see if it worked I before putting it in I have got a bad one once upon a time, as well as a bad new to me from parts store t-stat.  I verify they work.  I have a infra-red point and shoot temp gun that I use to measure the temp of the water to see the t-stat pop-open at the rated temp.  Same for switches.  only I use my DVOM to see them Pop closed at the correct temp.

Attach your dvom in Resistance mode or Ping, with the switch out of hot water it will not be 0 ohms, or ping.

Place the switch in a pan of water with the dvom connected, using a thermometer, or non-touch infra-red gun watch the temp of the switch in the water and write down the temp when the switch closes and goes to 0 ohms, or at the setting of the gun to match what is written on the switch usually 95C

If you can't get a single speed fan switch you can use a 2 speed fan switch by using solderless connectors one for the ground and one for the lower setting

Thanks so much Brian that’s great. Will do this tomorrow if I get a chance.

Further questions - could this also be related to the thermostat? Perhaps stuck closed?


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It's not just water flowing around the engine but around the switch which sits in a small gallery inside the rad, this can get bocked without blocking the rest of the rad.

Is it actually overheating and boiling up and/or losing water or are you panicking unnecessarily?

The only time the fan comes on is doing a 10 point turn or sat in an August heatwave for hours

One last thing to check, is your Battery to frame and frame to engine grounds.  If you make a 10 point turn and things come on or off, it is usually bad grounds.

An update for you all, it turned out to be a poor ground on my most 40year old wiring!! Thank you for all your help. I’m very glad it was something simple


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Guy94 said

An update for you all, it turned out to be a poor ground on my most 40year old wiring!! Thank you for all your help. I’m very glad it was something simple


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So you read my signature riddle?

I got taught a Big lesson in wiring by rebuilding a 58 Bug-eye (frog-eye) Sprite, then a 67 MG Midget, followed by a 72 Rover 3500 S… If Lucas is the Lord of Darkness, then Bosch is a Prince.

Only Lucas used wiring to protect the fuse at all costs.

I got educated in Bad Grounds by working on Aircraft, Radios, and Computers.