electric fan switch install: step by step guide needed

[bwv]

VWCaddy has on his website an excellent description of how to configure a switch inside the cab that allows one to manually turn on the electric radiator fan (w/o having to turn on the A/C) in case one is stuck in traffic and the temp outside is hovering near 90 f. His vehicle is an A1, but mine is an A2 (with A/C).

I know virtually nothing about electrical systems, and am really desperate to have one of these override switches on my Golf. I have tried unsuccessfully to make sense of the wiring diagrams in my Bentley.

Is there anyone here who has installed one of these on an A2 and would be kind enough to provide easy to understand, step by step instructions on how to configure such a switch. If not, I will gladly compensate someone for such advice.

Thanks

[Asymtave]

I don't have my Bentley here so I can't help with the wiring diagram for your car right now.

In general the cooling fan is turned on by a relay which is nothing more than an on/off switch that is controlled by 12V DC current. So, not being familiar with your car, but the temperature switch on the side of your radiator sends a 12V "signal" to the cooling fan relay when the coolant in the radiator gets above a certain temperature. This tell the relay to send electrical current to the fan to cause it to run.

I'm also guessing that on a car with A/C, when the compressor is turned on a signal is also sent to the cooling fan relay to tell it to turn on to help with A/C efficiency.

So in short you need to find the wire that tells your cooling fan relay to turn on. Then you'll do basically what VWCaddy did. You need to find a source of 12V that is on all the time while the car is running (radio power for example on my car, or a bunch of others), run that to your switch in the dash (that you add) and then from there on to the wire that tell the cooling fan relay to come on. Then you can "fool" the cooling fan relay into thinking that the radiator is too hot.

You'll want to just splice in, keeping the wire from the radiator switch intact as well so that still works if you forget to throw your new dash switch. So you'll end up with a "Y" configuration on the wires heading into the cooling fan relay.

Hopefully someone else here can give you a wire number/color today for your car.

[Asymtave]

Doing a little research here at work I'm betting you want to tie into wire # 85. I happen to have a cooling fan relay in hand.

So - find a source of 12V power when the car is running. Tap into this wire and run it to the new switch in your dash. Then run the wire from the other terminal on the switch and tap into wire #85 somewhere. I don't know what wire #85 looks like on your car unfortunately.

Eric

[tylernt]

VWCaddy has on his website an excellent description of how to configure a switch inside the cab that allows one to manually turn on the electric radiator fan (w/o having to turn on the A/C) in case one is stuck in traffic and the temp outside is hovering near 90 f. His vehicle is an A1, but mine is an A2 (with A/C).

Just out of curiosity, what for? Does your car overheat?

[bwv]

In general the cooling fan is turned on by a relay which is nothing more than an on/off switch that is controlled by 12V DC current.

Thank you for that cogent and easy to understand explanation. I will look up the wire and do some experimenting. You make it sound very easy, which is reassuring to me.

[Asymtave]

I'm on board with this. Just got my Caddy running again after an overheat/head warp. Nothing to do with the cooling fan, but bitten once, twice shy....

It makes me nervous in 90 degree heat just watching the temp gage rise when sitting in traffic or the drive thru line. (I guess eating less fast food would be good for my Caddy!)

Sometime well in the past the cooling fan relay corroded and somebody just wired the switch straight to the fan. This works, but eventually the switch is going to burn up or fuse shut. So I'll be restoring the cooling fan circuit to original this weekend, and think I'll put a auxiliary switch in the cab like discussed here, as well as a light on the dash to remind me when the fan is actually running.

Call it belt and suspenders, peace of mind, etc.

[bwv]

Just out of curiosity, what for? Does your car overheat?

Well, the car does not overheat, but like VWCaddy, I would like to have the option of pressing a button and cooling the radiator when the temp needle begins its slow movement from the center to the right side of the gauge. I would rather not wait for the fan to click on. Just an idiosyncrasy, I guess, which is sourced to my desire to have this car for another 7 years, at which time I will retire and no longer have to commute, and during that time not have to replace a head gasket or undertake a repair of similar scope.

[tylernt]

That's understandable I guess. I just went with a cooler thermostat and radiator fan switch though.

[VWCaddy]

Just out of curiosity, what for? Does your car overheat?

Well, the car does not overheat, but like VWCaddy, I would like to have the option of pressing a button and cooling the radiator when the temp needle begins its slow movement from the center to the right side of the gauge. I would rather not wait for the fan to click on. Just an idiosyncrasy, I guess, which is sourced to my desire to have this car for another 7 years, at which time I will retire and no longer have to commute, and during that time not have to replace a head gasket or undertake a repair of similar scope.

Just like I wrote on my web page:
- http://www.4crawler.com/Diesel/CheapTri ... rFan.shtml

Just run two wires back from the fan switch in the radiator to the dash and wire to a SPST (Single Pole Single Throw) switch. All you are doing is simulating the radiator fan switch closing with you close the switch. Then whatever the radiator fan switch would cause to happen will happen (i.e. the radiator fan will come on).

[Asymtave]

This is a much better solution that what I proposed.

Eric

[bwv]

Just like I wrote on my web page:
- http://www.4crawler.com/Diesel/CheapTri ... rFan.shtml

Just run two wires back from the fan switch in the radiator to the dash and wire to a SPST (Single Pole Single Throw) switch. All you are doing is simulating the radiator fan switch closing with you close the switch. Then whatever the radiator fan switch would cause to happen will happen (i.e. the radiator fan will come on).

Thanks... for me the problem is the terminology. When you say "fan switch in the radiator" I am not sure what you mean (forgive me for being dense). Is that the fan relay?

I will post some photos in a few hours and hopefully we can figure this out. Thanks for your patience.

[VWCaddy]

Thanks... for me the problem is the terminology. When you say "fan switch in the radiator" I am not sure what you mean (forgive me for being dense). Is that the fan relay?

I will post some photos in a few hours and hopefully we can figure this out. Thanks for your patience.

Find the radiator at the front of the vehicle, move over to the side of it next to the battery and reach down the side of the tank and there you will find the radiator fan switch (Bentley manual refers to is at the "Thermo Switch"). It screws into the hole that is just below center on the left side of the radiator pictured below:



It is a thermo-switch that screws into the side of the radiator to sense the temperature of the coolant. When the temperature inside exceeds the switch's rated value, it closes a pair of contacts inside and that in turn sends power through the radiator fan relay (if there is one) and that in turn sends power to the radiator fan.

[bwv]

Find the radiator at the front of the vehicle, move over to the side of it next to the battery and reach down the side of the tank and there you will find the radiator fan switch (Bentley manual refers to is at the "Thermo Switch"). It is a thermo-switch that screws into the side of the radiator to sense the temperature of the coolant. When the temperature inside exceeds the switch's rated value, it closes a pair of contacts inside and that in turn sends power through the radiator fan relay (if there is one) and that in turn sends power to the radiator fan.

OK, now I know what you are talking about. I was looking at some of the relays and wires at the top of the radiator, which is why this was so confusing to me.

So I simply splice a couple of wires to those emanating from the thermo switch, and attach them to an SPST, which is placed in the cab, Sounds simple. (We'll see. )

[VWCaddy]

OK, now I know what you are talking about. I was looking at some of the relays and wires at the top of the radiator, which is why this was so confusing to me.

So I sinply splice a couple of wires to those emanating from the thermoswitch, and attach them to an SPST, which is placed in the cab, Sounds simple. (We'll see. )

Easy enough to test your setup. Unplug the connector at the fan switch and shove a jumper wire across the pins (easy if it is a simple 2-pin switch) and the fan should come on. If it is a 3-pin switch (used for the 2-speed fans) then you'll have one pair of pins to make the fan run slow and one of those pins and the other one will give you high speed operation (I don't have one of those so can't tell you which pins do which). Once you determined that you can control the fan with the jumper wire, it is a simple matter to strip back the insulation from the two wires, wrap your new wires to that, solder for a secure connection or use a crimped wire splice connector, wrap w/ electrical tape and then run the wires to the cab and install a switch. Again, you can easily test the setup once you have spliced in the two wires by connecting to the switch and turn the switch on and off and make sure the fan works.

Note that not all vehicles have a fan relay, that is usually associated with vehicles equipped w/ A/C or ones that have 2-speed fans AFAIK. If you have a fan relay, then you can use any old switch and pretty much any size wire as all you are switching is the power to the relay coil, typically under 1/10th of an amp. If you have no fan relay (as my non-A/C '82), then the wiring and switch need to be rated to handle the fan motor current. When I get around to adding this to my '82, I'll add a relay to control the fan (terminal 30 to the battery, terminal 87 to the fan motor, terminal 85 and 86 to the old fan motor wires - this way the switch turns the relay on and off, the relay turns the fan on and off).

[bwv]

If you have a fan relay, then you can use any old switch and pretty much any size wire as all you are switching is the power to the relay coil, typically under 1/10th of an amp. If you have no fan relay (as my non-A/C '82), then the wiring and switch need to be rated to handle the fan motor current. When I get around to adding this to my '82, I'll add a relay to control the fan (terminal 30 to the battery, terminal 87 to the fan motor, terminal 85 and 86 to the old fan motor wires - this way the switch turns the relay on and off, the relay turns the fan on and off).

I have A/C, and unless I am mistaken the fan relay is at the top of the radiator (I think its white, cube-shaped, about 1/2" per side). But I am not fooling with this cube, correct? All I am doing is adjusting the wiring at the fan switch itself... EVEN though I have the relay. But since I DO have the relay I can use a switch that is rated below what is needed to handle the fan motor current.

This is where it gets confusing for me, if you could not already tell. LOL