Odd e-fan questions/problem.

[Fett]

The setup: Taurus fan, VW switch, 70amp relay. I have a jumper wire going from the + on the compressor to the trigger wire into the relay, with a diode in the middle to keep power from backfeeding into the compressor when t he fan comes on with the AC off.

The fan was working perfectly, coming on when need be, shutting off when not needed. The stock temp gauge never got to half way (where it used to sit with the clutch setup. Tonight I was doing something stupid....kind of. Tomorrow it goes to the track for it's (and my) first time. I will be running slicks and wanted to practice my burnout...I know, I'm a rookie. Anyway, after doing two my car started running hot. I didn't hear my fan kick on. When I would shut the car off but leave the key on ignition, the fan would kick on. I tried turning on the AC with the car off and the fan would kick on like it is supposed to do. But if I turned on the AC with the car running, the car would die. I tried it while driving, as soon as the AC turned on the car would die, if I was sitting stopped with the car out of gear, holding the RPMs at about 2k and turned the AC on, the car would die.

Basically as soon as I turn the AC on with the car running, in any condition, the car would die. And my fan will not turn on with the temp...but it does work with the AC...when the car isn't running.

I am thinking that I might have two problems. The car never really was running great with the AC on since the fan install in the first place (yes I have the 130amp alt and all correct upgraded wiring). I am thinking that maybe I blew out too much coolant and the sensor isn't picking up the coolant flow because the level is such that it is not getting to the VW sensor/switch. Obviously I can't tell that until the car cools off. I just installed a Moroso catch-can/overflow tank with nothing in it...so I am thinking that might be the source of my "fan not coming on with the temp switch" issue.

But the AC compressor is quite something else. I usually don't use my AC, which is making me think of removing it anyway...but since everything is there and works....until now....if it is something easy I might just fix it.

I don't see where the AC compressor and fan would be too much for the 130 alt....and I don't have any charging issues. This whole time my stock volt gauge is sitting nicely above 13.

 

[Fett]

Ok, I checked and my coolant level is fine. I pulled the plug out of my compressor to see if the compressor kicking on was causing the engine to die, and it isn't. With the AC compressor unplugged and I turn on AC on, the engine would still die...so it is an electrical issue.

So I reconnected the compressor but cut the wire leading to the trigger, so the AC compressor would have nothing to do with the fan coming on. Turn on the AC with the car running, and it came on with no problems. But the fan still won't kick on when the temp rises.

However, if I get the temp to where the fan SHOULD kick on, then turn the car off...but turn the key to power ignition...the fan comes on.

So it seems that the fan itself will not run with the engine running....but if the engine is not running it will work fine. Basically the fan itself is killing the engine...and it won't power on by itself when the engine is running...and when I force it to come on, the engine dies.

 

[Fett]

Ok, today I unhooked the trigger wire from the VW switch and ran it directly to the battery and the fan works. It obviously stays on the whole time, but that is working. So I am thinking it might be an issue between the ignition power wire and the switch itself.

For my ignition wire I just probed until I found a wire that was dead with the ignition off and had power with the ignition on...but I honestly dont' know what I tapped into. That could be an issue....or it could be the VW switch. I don't have a diode inline from the switch, so maybe that is a problem. I don't know how to test the VW switch.

 

[jrichker]

There is no indication of the year model of your car. The electrical system & wiring changed several times over the 79-93 time period. No model info, no clues as to what wiring could be at fault.

That's why it is a good idea to use the sig under the user control panel (User CP) option. It allows you to post your car year & mods, which help greatly when troubleshooting things. No, it is not there for us to snoop and see any "Secrets" you have hidden away under the hood. Be a good stangnetter and update you sig for future reference & don't keep us guessing.

The term VW switch is rater vague, please explain.

 

[Fett]

Sorry about that....I tend to forget the important details. Unfortunatly though, I can't be too specific about the year and whatnot. It was originally an 88 2.3, but was converted before I bought it. It was speed density, but the harness had a MAFS connector...so I believe the engine used was a pre 90 engine, but they used a 92+ harness.

The VW switch I am talking about is a 83 VW Rabbit thermoswitch. I followed a how-to on using it. Basically it is a stock VW switch that turns the fan on at 198 and turns the fan off at 189, using a 180 thermostat. It is tapped into the thermostat housing.

It is wired as such:
A wire running from an ignition hot wire into the switch, then the other side of the switch runs to the 70amp relay as a trigger. The relay is wired with 12 from the battery and battery ground. Everything was wired up correctly, as far as I can tell. The only questionable part is the ignition hot that I used. I basically just probed wires until I found one that only lit the test light with the ignition on...and it was working fine for a day. That is when all the weirdness started as stated in my first post.

I tested my ignition trigger with a voltmeter and found that with ignition on/engine off it was putting out 12v. With the engine running it was only putting out 3v. So I probed another wire that was giving out 12v with ignition and with the motor running....but still nothing.

The fan itself works if I connect the trigger wire from the relay direcly to power, but it won't work through the switch any more. I am thinking a few things...

1) I choose a bad ignition 12v source.

2) The switch is bad....I don't know how to test it.

3) I have a short.

4) Not having an inline diode on the trigger wire on the relay side of the switch caused backfeeding of power from the relay...causing issues.

I don't know. I talked to a guy at the track today who just installed the same thing, and did it exactly like I did....except he is only using a 40amp relay and his is working fine.

Also, I noticed that when the fan was working with the switch....the fan would KICK on hard, you could see the whole fan assy twist with the initial startup. Where as when I just hook the trigger wire directly to the battery to get it to work, it doesn't KICK like that. It just starts up and doesn't cause any idle stumble...like it does through the switch.

 

[jrichker]

Some wiring diagrams...

Diagram courtesy of Tmoss & Stang&2birds

Control wiring:
Use 18 gauge wire and tap into the red/green wire going to the ignition coil to power the relay coil. That way the relay will only have power when the ignition is on. Connect the other side of the relay coil to one of the wires on the thermostat switch. Connect the other side of the thermostat switch to ground.

Optional manual override: Connect one 18 gauge wire to the relay coil wire that connects to the thermostat switch. Connect that wire to one side of a common toggle switch. Connect one 18 gauge wire to ground and the other side of the toggle switch. That way when you turn the switch on, it bypasses the VW thermostat switch and turns the relay on. The fan will only run when the ignition switch is in the Run position. This will save your battery if the override switch is accidently turned on while the engine is not running.

All the control wiring I have descirbed is operating in current sink mode. That means you provide a ground to make the circuit work. It also reduces the number of fuses needed for the circuit.

Power wiring:
Connect one 10 gauge wire to the battery side of the starter solenoid and connect it to your 30 amp inline fuse. Connect the other side of the fuse to the relay switch contact. Connect another 10 gauge wire from the other relay switch contact to the fan power feed. Connect the other 10 gauge fan wire to ground. Note that reversing the fan power & ground will reverse the direction of the fan.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[HISSIN50]

JR, he's using the VW fan thermal-switch that Mr Smith notes in his Mark 8 article (at least I think I recall seeing the switch mentioned there). EDIT: you posted while I typed and played with the dogs.

Chris, that was a lot of posts to sift through. Have you disconnected the ignition switch input to the relay (the wiring that you still need a blocking diode for) and seen if the car dies when you turn the AC on? I'd want to rule out if it's a coincidental issue with the stalling, or if it's related to the new fan wiring.

About the best way I know to test the switch is to put it in a pot of water on the stove, and use a cooking thermometer as a reference. Note if the switch closes at whatever the temp threshold for it is. Be real careful of course.
Or let the car idle till you are in the neighborhood of it being ready to close and see if you get continuity across the leads.

it seems to me that diode for the VW sensor is to keep inductance from the relay from backfeeding the ignition source you chose. I suppose if it was something sensitive, it could have made some difference (you couldn't have had a VREF wire instead? Backfeeding 12 volts into a VREF circuit could be bad). I doubt that happened, but it was worth asking.

Good luck bud.

 

[Fett]

So you are saying I should use the VW switch for negative and not positive? Someone else suggested that...but I was trying to go with the how-to.

I actually removed the AC from the equasion all together because I thought that was the problem....it wasn't. So at this point, the AC being on doesn't effect things. To take it to the track today, I took the trigger wire off the switch and ran it directly to the battery and the fan stayed on the whole time. Basically I removed the wire when I shut down and rehooked it back up to drive. Doing that and turning on the AC, everything worked fine.

So I am thinking that it was a power to the fan while the motor was running problem. But it works fine when I remove the 12ignition hot wire and the switch. So I know the relay and rest of the wiring is fine. The problem has to be in either the switch or the 12v ignition wire that I choose.

 

[HISSIN50]

I was surprised to see that Luke had chosen to use the VW thermal switch to pass 12 volts. I honestly dont know how it was designed to work in OEM form though (this stuff is right up electrical whiz Jrichker's alley). I personally would have tried to use it switching ground, only because that's what I'm familiar with.

So with the VW switch part of the wiring disconnected from the relay, your car doesnt die any more, etc (I think). Cool.

I'd simply try another 12 volt feed source for the VW switch and relay coil. I really like to know what circuit I'm tapping into for things like relay coils (even if it requires me to run a wire to the wiper motor, interior fusebox, etc).

If that takes a dump again, I'd think about another method (switching ground if feasible, etc).

But like I said, JR is the man with this stuff - he might have some valuable input.

Good luck Chris.