Wiring a VW temp sensor in line with a fan and relay

[SRSANDS]

Today I started researching how to wire the vw temp sensor thats in my radiator to a relay and my new fan. After researching for hours I still didnt come up with much as far as the schematic on the sensor. I did learn the RED wire on the sensor is common and the other two are two different degrees, RED/WHITE is 203deg and RED/YELLOW is 221 degrees (for a two speed fan). But I friggin just stare at the components and are dumb founded on how it all goes together. I wired my headlights all up using relays and it worked perfect but now Im stuck. My plan is to use temp switch on the ground side of the fan. That is as far as I could get. Could any wire gurus lend a hand so I can get this small job done. Thanks in advance...and dont tell me to use the search button :) If I dont need a relay then its simple....fused power to the positive fan wire, ground from fan to one of the wires (not what degree to use) then common from the switch to ground or visa versa on he switch fan ground to common on switch and from degree wire to ground eh? I think im just looking to far into this.

 

[DanielC]

This is how I would do it. I am assuming the VW temp sensor has power go in the red wire, and at some temp, passes that power to one of the other two wires, and if it gets even hotter, it connects the other red/yellow or red/white wire.

 

Power from the ignition switch goes to the red wire on the temp sensor. Red/yellow temp sensor wire goes to terminal 86 on the relay. Terminal 85 on the relay goes to a good ground.

This makes the relay go on and off. You need to make sure the body of the temp sensor does not have 12 volts on it. At this point, you can turn the key on, and listen for the relay to click. It should not. Gently heat the temp sensor by using a match, light bulb, or a lighter. Do not use a blow torch, it could quickly get hot enough to destroy it. You could also find out which wire is the higher temp wire, with a little experimenting.

 

From the positive side on the battery, put an inline fuse. Then go the the positive side of the fan. From the negative side of the fan motor, go to pin 30 of the relay. Ground pin 87 of the relay. Use a heavy gauge wire for the fan motor, all the way from the positive battery terminal, through the fuse, the motor, and the relay and to ground.

[yello620]

30 on relay-battery power

87 on relay to fan positive, fan negative to ground.

85 on relay to temp switch output(wichever degree setting you prefer)

86 on relay to keyed power, battery power if you want them to run after you shut motor off.

red wire on sender to ground.

 

This should allow the switch to create the ground for the relay at your temp setting. Grounding the relay should turn the fan on. You could also wire a swich in to create the ground so that you could turn the fan on anytime you want to.

[SRSANDS]

Thank you for the knowledge.....I will give it a shot :)

[yello620]

updated previous post a little. Left out the need for fuses.

[DanielC]

Here is my quick and very dirty addition to your drawing.

[johny5]

I dont think the switch needs a relay ,Im sure it wont hurt, Im almost positive they dont have any type of relay in the VW ,

 

I ran this same switch ( from a jetta ) with out any relay no problem

[yello620]

Here is my quick and very dirty addition to your drawing.

 

 

This is an interesting way to wire a relay, i dont ever remember seeing it done that way. Yet, i dont see a reason it would not work, maybe even work really well because the battery power is going straight to the fan, not even through the relay, then fan.

[Unclejesse88]

This is an interesting way to wire a relay, i dont ever remember seeing it done that way. Yet, i dont see a reason it would not work, maybe even work really well because the battery power is going straight to the fan, not even through the relay, then fan.

All he is doing is using the relay to switch ground instead of positive. Either way works.

[DISLEXICDIME]

All he is doing is using the relay to switch ground instead of positive. Either way works.

 

a vw runs hotter then a l series watch out for your head gasket

[72wagun]

I dont think the switch needs a relay ,Im sure it wont hurt, Im almost positive they dont have any type of relay in the VW ,

 

I ran this same switch ( from a jetta ) with out any relay no problem

 

You're right. You don't have to have the relay, but it's not a bad idea. My dad had a Rabbit for years. It didn't have a relay from the factory. After replacing the temperature activated switch several times he wired in a relay. He never needed to replace the switch or relay after that.

[SRSANDS]

a vw runs hotter then a l series watch out for your head gasket

 

Im working on a VG install, all the nic nac crap takes alot of work. Not sure what temp a VG runs at but I will check into it akso...thanks, and thanks for the info and diagram.....off to the garage I go

[DanielC]

I figured since he had a 510, he was used to the relay switching the grounds, like the headlights.

Besides, doing it that way, for the ground wires, you need just a short jump from pins 85, and 87 to ground, maybe with the same screw that mounts the relay.

It is not that my way is better or worst, it is just one way of doing it. There are many other equally good options.

[qwik510]

Im working on a VG install, all the nic nac crap takes alot of work. Not sure what temp a VG runs at but I will check into it akso...thanks, and thanks for the info and diagram.....off to the garage I go

 

 

Did you find out what temp the VW switch turns on at?

[SRSANDS]

Ya it turns on the fan at 203 degrees....I hope thats a safe point to do so :) What you think?

[paradoxx]

I think that will do.....but isnt better a 195°?.....I know VW engines run hot but im just guessing..

[fo0manchu]

I've always known nissan engines to turn on at 180. At least thats when most of their thermostats crack open. I would want mine to turn on a little bit before the thermostat opens, that way the temps should stay pretty constant.

[SRSANDS]

Ya I am a little worried about that too....I guess I will will find out how it does once the beast is alive and then swap it out for a s12 one if I need to

[SRSANDS]

Researched and learned the vr6 switch kicks on at 190 degrees......gonna go grab one

[260zkaboom]

It looks like the connection to the temp switch should be to the red with white, so the fan to come on earlier instead of red with yellow which is closer to over-heating

[bonvo]

read the write up on the rabbit radiator install and it has a partnumber for a 180 degree switch

[SRSANDS]

Read the write up for the rabbit rad and tell me the part number would ya!? JK......where is this write up you speak of and I will read it