Radiator fan not engaging

Hi - i was just wondering if there was anything obvious people could suggest to help me solve a problem

My car (1993 cab) overheated last weekend and on inspection, it was clear that the radiator fan was not working.

I removed the connection to the radiator fan temp switch and bridged the connection and the fan came on so I assume that all is well with the fan motor and the wiring.Today I replaced the fan temp switch, ran the car until it was over 3/4 of the up the heat gauge and still the fan was not kicking in.I am just not sure what tthe next steps are to locate where the issue is or what I need to do to get the radiator to kick in when it is meant to.

Everything up to the switch seems ok. I assume the new switch is working. The connectors seem to be in good condition. Is there some way that the switch itself is not heating up? For example, f the pump is not working then would this also stop the radiator switch from triggering?

Any suggestions? This has is beyond my limited knowlede.


Richard

I would try another switch, or test the one you have.

  You can see if the water pump is pumping, when cold with it running, if you look in the expansion tank should have a stream of coolant coming from the small hose.

 also when its warming up check if your bottom hose on the rad heats up as it wont flow through the rad if the thermostat is stuck shut so could possibly be that.

On the 90's cabriolet there is a relay to the left of the battery, that controls the fans.

That is a standard 40 amp bosch relay that folks use for after market ralley light adds.



It is quite common for it to go kaput, as it isn't water tight and is subject to battery outgassing and water migration.  I have had 3 90-ish cabriolets and that relay has been bad once on all 3.  It will prevent the fan from coming on.  It goes bad either full on, (fan runs all the time) or fan don't run at all.  (I have had both types of failures)  fortunately for me it broke the runs all the time in my garage….

i know this was quite a while ago but im having an issue with my fan too but i cant find the relay under the bonnet where yours is, its a 91 Karman Clipper where do you think mine will be?

Briano1234 said

On the 90's cabriolet there is a relay to the left of the battery, that controls the fans.

On one of mine it was laying loose near the battery, until I found the bracket that it should of been attached to.
The relay is a standard Bosch 53 relay.



You can find the wires off the Fan or the Radiator fans switch and trace them to the relay.

I don't think UK cars have that relay?
Brino1234 do you have a twin speed fan as that could be why you have the relay?

Yes I do have a 2 speed fan.
But try this, on the valve cover rear right side as your are looking at it there is a large Brass Screw with a single brown wire on it.  Short that to ground, and see if the radiator fan runs, if it doesn't then jumper the fan from the red lead to the battery, and then the brown lead to ground if the fan doesn't come on then your fan is bad.

High suspects are the radiator fan switch, and the fan itself.
Here is the Bentley for the non-a/c fan.

great ill try that in the meantime ive ordered a fan and switch as the fan was looking pretty beaten up and very weak when connected (it stayed on, so i unplugged it!)

Then look at your valve cover for that large brass screw with the single pin, it is the after run fan switch, and if the brown wire is off, and shorting to ground, then your fan should run all the time.

when i removed the switch half of it has coroded away, no wonder it wasnt working, so much gunk on the inside of the brass end !!

So inserted new one and the fan is now sorted!

Now i have a problem with it stalling after sitting for a while but i think that might be mixture…

If the end of the switch had corroded away how old is your coolant and what colour is it?

it was kinda bluey green, i have bought some more so will refill using that, cheers for the advice

on a side note ive been reading a lot about the GTIs issue with fuel going round corners and feel like i have the same issue with my 1.8clipper going up hills with less than half a tank. it recently cut out completely while i was waiting for someone to manouver a country lane and now therese no fuel reacing the carb.  weird thing is that the fuel pump has some pressure but not making it through the vaporisor, ive checked all the hoses and no blockages.??  could the pump have failed while i was trying to restart it with no fuel in the system? and now its working but only weakly?

Yes, that is one possibility, Electric fuel pumps use the fuel to keep it cool when running, as well as a lubricant for the twisty bits.

The swirl pot keeps the fuel in a place where it can be picked up by the pump when you are in a turn or up a hill so that when you are low on fuel and it moves from one side of the tank to the other as in a INCLINE, or Hard Turn, the pump and engine doesn't get starved for fuel.

Carbs have bowls to feed the jets, so it isn't as much of an issue but Injected ones need it more.

On latter Cabriolets 84.5 to the 90's, in order to more cost effectively streamline the process, VW increased the size of the Tank from 10Gal, to 13Gal, they took the internal swirlpot out of the tank and made it external. They change the name to (filter).

They also used a lift pump in-tank to provide fuel to the swirlpot.

84.5 to 89 over here used a 75psi fuel pump as a main to feed the cis injection system. (ok the early ones had the same pressures), which is why you have banjo bolts.

The 90's and conversion to Digifant Streamlined the fuel system, and the main pump was changed to a lower pressured 45psi.

In a Digi the fuel/injection system was streamlined, and a lot of the adjustments and restrictions were removed, but the engine management was put on a different ECU, and a couple of added sensors, as well as electric fuel injection. Where as the CIS used Mechanics for injection.

IMHO Digi is easier to maintain, and tune.
 

great info thanks!
So my 91 carb version doesnt have a swirl pot only a filter, right? would it help to add another filter to store more fuel in the line?
im going to try and keep the tank almost full and see if that changes the situation

Don't get confused, the later cabby's had a 13 Gallon tank, they didn't have an internal swirlpot.

Vw use a lift pump in the tank, and a swirlpot / filter on the right side of the tank.

This res/filter/swirlpot is what feeds the primary pump on 84.5-93 Injected (CIS or Digifant).

Ah i see. So is there a solution to the carb versions lack of swirlpot? i have read other threads but they are mostly about the injection version.  

I have never needed a swirlpot on a Carbed Car if the fuel pump is good, as the pump pushes fuel to the bowl, and the jets drink from a bowl. You tank does need to be clean and devoid of rust and crapola.

I have only had experience with a 58 Bug-eye, 67 Midget, Rover3500S all SU side draft carbs, and then there my 2 76 Toyota's,  89 Oldsmobile with a Holley 4 barrel over the years.  My 67 MG and on up had electric fuel pumps.