Hello All,

I will be finalizing my electric fan wiring as soon as I have all the parts. I have two fans, the volvo relay and a generic( I don't remember it's name) thermo switch in the thermostat housing. My, hopefully, last question is will the BMW thermo switch( part #61318361787) wired through the volvo relay run two fans at the same time or one fan at two different speeds?

 

The Volvo relay pack is designed to be used with a single, two-speed fan. That means there is one + wire for low speed, and one for high. Running two fans with it would mean running a Y off each positive lead, and that would cut the power to each fan by 50%.You might be better off to try to fit one Volvo two speed fan. (35amp fuse on low, 65amp high)
Note: The Ford Contour came with a nice dual fan system that is only 3.25" thick at thickest point. It works well, but not with the Volvo relay pack. The bmw thermo switch will work with Volvo relay pack. But check it to see the temp rating, when it turn on and off. Make sure it will work with the thermostat you have in your vehicle. Take my system for example. I use a 195* thermostat. My thermo switch turns the fans on at 205*. That means I can cruise the freeway w/o the fans turning on. The thermostat keeps the engine, along with a massive amount of air flowing through the radiator, at 195*. But when I get off the freeway and stop at a light, the temp climbs and the fans switch on. You want your thermo switch to turn on the fans at about 10* hotter than your thermostat. Also, make sure your alternator is putting out enough amps for your fans and everything else. Good luck.

Below is the Volvo fan, with the 65amp and the 35amp fuses the factory used on it. I mention this fan b/c it is the smallest of the Super fans at 14"
Attachment 277821

And here is the Contour dual fan system. Both fans are one speed, but Ford ran the low lead through a resistor to syphon off some power and thereby created a low speed. High speed bypassed the resistor and supplies full juice to the fans.
Attachment 278373

 

Sorry for the delay, life is kinda crazy right now. The way it is currently wired is the one temp thermo switch to the #1 input of the Volvo relay and the #1 output to fan#1. This setup works except in stop and go traffic on hot days. I live in Florida, every afternoon is a hot day. What I want to do is have the BMW thermo switch post #1 to the Volvo relay input #1 to fan #1 and then the BMW post #2 going to the Volvo input #2 to fan #2. Fan #2 is larger so I’m assuming it is the high speed/high volume fan. If I wire it this way will the BMW switch try to run both fans or only the second fan? Also, I already did the 3g upgrade with all the necessary wiring for that.

 

Hey there. Theoretically that will work. However, fan two will kick into high speed from a cold stop. That will cause a large spike of power going from battery to the fan, and your ignition may stumble for a second, and it may blow fuses or fry wires if not adequately set up. You'd be a lot better off to get a single two-speed fan, and run it through the Volvo controller with a bmw thermo switch. A Taurus or Volvo fan would be perfect and supply way more cooling than you need. What are the fans you're using now? If the one you're using for low speed is not doing the job, and it's a decent fan, then maybe you should ask yourself why it is not cooling well enough. Is you radiator in good shape? your thermostat?
You can pick up a good used Taurus or Volvo fan at the Junkyard for around $50, and it'll come with the built in shroud.

P.S. Looking back, I see that I did not fully answer your question regarding the volvo controller. If you wire the fans and controller as you mentioned, the low speed will kick on when the temp reaches the temp needed to trigger low speec activation. If/when the temp continues to climb and triggers high speed, low speed shuts off and high kicks in. That's the beauty of the volvo controller. But, as I mentioned before, b/c you're using two fans, the second fan will go from stop to high in an instant. The following spike or surge in power would not have happened with a two-speed fan because it would already be spinning when the high kicks in. That spike might fry relays or wires or fuses that would not have gotten cooked had it been wired as the factory wired it. Good luck.

 

The fans I have were pulled from a Taurus but I think it was an 05. I can’t remember exactly. I do remember the single fan with dual speed was not at the junkyard that day. I picked them bc I’m 45 miles from the nearest self-serve junkyard and I figured a modern high temp running engine would have good enough fans for these old trucks. The fans are two different sizes and I’m assuming the larger moves more air. I may have to bite the bullet and hold out till I can find a dual speed fan … sigh

 

There is always ebay, Amazon, RockAuto. Or, if you want to go a diff. route, you could keep the fan you have and just purchase a PWM controller. That type of controller will only feed the fan enough power to cool the engine, determined by the temp of your engine.

Take a look at Auto cool guy. His units beefier than the mass produced ones. He is a garage shop. I am not affiliated in any way.
https://www.autocoolguy.com/home

https://www.ebay.com/itm/31074305282...gAAOSweXRh69B~
https://www.rockauto.com/en/catalog/...+assembly,2181

https://www.ebay.com/itm/22493585165...8AAOSwaiZiVubV

 

I got the BMW thermo switch delivered. I’m gonna install everything this weekend and clean up all the engine bay wiring. My question is this, does the “O” post on the switch get wired as a ground or receive 12V power?

 

I did the wiring for post 1 and post 2. I used a jumper wire on post “O” to battery positive and the plan was to let it idle until the fans kicked on to make sure everything worked. The fans never came on. My temp gauge on the dash was on the line outside of the normal marks and my IR heat gun said the BMW temp sensor was 204 degrees and the block around the stock temp sensor was 210 degrees. After I let the engine cool off I wired the “O” post to the battery negative side. This ended with the same results, but I stopped the test at a lower temp. What am I doing wrong? I reread the Z28 post about electric fans and it does not say specifically how the BMW switch is to be wired. Help is definitely needed and will be greatly appreciated.

 

Whoa. The bmw thermo switch needs some sort of controller. If you ran it straight to battery + you may have ruined it. The thermo switch only connects ground, completing a circuit. NO CURRENT FLOWS THROUGH THE THERMO SWITCH. When your coolant (you absolutely need a temp gauge that you can read the exact temp on, not the oem gauge w/o a scale) reaches a certain temp, the switch grounds the system and current is delivered to the fans. BTW, your block temp is going to be different than your coolant. The thermo switch is activated by the coolant temp, not the block temp.

Use that thermo switch for what it was designed for: a single two speed fan. If you are trying to run dual fans with high and low speeds, you are going to run into problems. Electric fans are no joke. They can be dangerous. They take a lot of amps. That means that quality wire, quality fuses or circuit breakers, and quality relays are required unless you want to risk a very real fire hazzard.

Get a cheap Sun Pro temp gauge.
Get quality wire.
Find out how many amps your fan or fans use on low and high.
Wire in a good fuse on the + wire.
Get a Bueller relay that can handle the amps you're going to run through it.
Get a soldier gun and soldier ALL connections.
Get a lot more knowledge before you proceed.

One two speed volvo or taurus fan will cool an engine with cooling needs far beyond those of your engine.
The wires coming off the bmw thermo switch are like 20 gauge. The wires that carry power to most efans are 10 gauge. The fact that you connected + to one of those leads, that scares me. With all due respect, you need to read more threads about wiring one of these fans before you go any further.

Attachment 278116

 

Ok … the BMW switch post 1 and post 2 are wired to the Volvo relay. I’m under the impression these are used as signal wires to the Volvo relay which I have running fused connections from the battery through the relay to the fans. I know 20 gauge wires are too small to handle the power directly from tue battery. Sorry I didn’t fully explain the situation. I was trying to keep it simple and figure out how the “O” post get wired. Is there any way I can test the BMW switch to see if I ruined it?

 

Wire up the thermo switch. Place the business end in a pan of water. Heat water and watch a thermometer in the water. See if one or the other circuits activates when the temp in water reaches the switch activation temp.

 

I noticed the BMW dual temp switch listed in this thread switches at 80c/176 freedom units & 88c/190.4f. I cant seem to find any others. I've got a 390 which I think the typical thermostat opens at 180* (please correct me if that's not right). Seems like the Beemer switch wants to run way cooler than our trucks? Is 190f too cool or would the fan on low mostly keep the temps low?

 

After checking at Rockauto, it looks like the oem thermostat is 195* for a 390 FE. That mean that a thermo switch that opens at about 205* would be perfect.
BMW switch #61311378073 low speed opens at 195*F and high at 210*F
BMW switch #61318361787 176*F and 190*F

There is also the Beck/Arnley switch that came iirc in VW's and audi's. I'm now running one. If you check around for thread on various forums you'll find the temp for these two speed fans. Since I have a dual fan system, I use the high speed side of the B/A switch that kicks the fans on at 210*F. With my 195* thermoswitch, it works well. I prefer the bmw switch b/c the threads are much smaller, and there is a 90* cap for the wiring that looks slick.

 

So to that I understand, you are running the high side of the switch only? And for my own edification the theory behind two stage cooling either single or dual fans is that the low side will keep it from constantly cycling the full current and hopefully make it easier on the system? Might be getting into the weeds here, modern vehicles will kick the fans on as soon as you hit the AC button, the Volvo relay doesn't have an additional terminal is there a signal that comes from the ac to kick the fan on as well spliced into one of the signal switches?

 

Certainly there is some way that they do it, but I'm not ware of how that is done.