All right, I about lit my car on fire this afternoon and I think I may have a bad relay. I need some electrical advice in a bad way!!

I was installing my controller when my ground wire from my gauge pod melted and turned red. After the smoke and smell went away I got back in there and started taking some readings with my multimeter.

Here is a link to the instructions for the fan controller:
http://www.dakotadigital.com/pdf/pac-2700.pdf

My main question concerns the lower right hand side of the 1st page labled "single fan."

When I take a voltage reading from a known GROUND to the black wire on the relay (fan ground) I am getting a 12 volt reading. I know this is wrong and the only place it could be coming from is the +12 (green & red wires). Maybe I just answered my own question, but do relays fail like this? Seem like they should fail in a way that wont start a fire!

Also, just to be sure...GROUND is GROUND right? Meaning I have the fan grounded in the engine compartment and the relay is using a common ground under the steering column(shared with the gauges). Is this OK?

I am a little scared to hook everything back up!

Let me know what you think about the relay and the ground PLEASE!

Thanks
Jason

Jason I'd like to help but don't fully understand your question.

First, take the red and white wire out of the equation. They are relay control and not enough current to drive a big fan.

Now, that "green" wire, the fan power 12+, what happens when you bypass the relay and apply 12v+ to the fan? Fan turn on? Smoke?
A relay is like an off/on switch. It will not "short" to ground. The contacts could "fuse" [meaning weld themselves] together, but all that would do is cause the fan to run all the time, not cause wires to turn red-smoke-and burn.

A ground is a ground. I suspect you tied into a non-ground. Just because a wire color is black, by no means make it a ground. Want to be certain you have a ground? Tie off to a metal support under the dash, or any other metal structure where you see a factory crimp lug screwed to ground.

Long story short, don't blame the relay. Relays are your friend.

Can you post a pic of the relay with the brand ?

They can be wired up NO (normally open = off) or NC (normally closed = on)

Sounds like a crossed wire or bad relay ??

This is for a Bosh relay so your numbers may be different :yes:

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglite.jpg

Jason I'd like to help but don't fully understand your question.

First, take the red and white wire out of the equation. They are relay control and not enough current to drive a big fan.

Now, that "green" wire, the fan power 12+, what happens when you bypass the relay and apply 12v+ to the fan? Fan turn on? Smoke?
A relay is like an off/on switch. It will not "short" to ground. The contacts could "fuse" [meaning weld themselves] together, but all that would do is cause the fan to run all the time, not cause wires to turn red-smoke-and burn.

A ground is a ground. I suspect you tied into a non-ground. Just because a wire color is black, by no means make it a ground. Want to be certain you have a ground? Tie off to a metal support under the dash, or any other metal structure where you see a factory crimp lug screwed to ground.

Long story short, don't blame the relay. Relays are your friend.



I will have to try bypassing like you said when I get home.

Its interesting because the instructions I have that came with the kit show the red & green wire "coming together". The instructions have been changed/updated since I bought my kit to show the green "fan power" & red "+12v" seperated (which makes sense). I am going to call Dakota today because this means the green wire should be run directly to the fan correct? I admit I didnt get too far before i had to stop and step away, but the way my instructions show the fan would have power all the time.

When I get home I will get my instructions and scan them and maybe you all can tell me if the change was significant.

Thanks.

Can you post a pic of the relay with the brand ?

They can be wired up NO (normally open = off) or NC (normally closed = on)

Sounds like a crossed wire or bad relay ??

This is for a Bosh relay so your numbers may be different :yes:

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglite.jpg

Definately not a Bosch relay. It was supplied with the kit and was not a brand I had ever heard of before.

Thanks. I am goin to call dakota today from work if I get a chance because of a change in the instructions mentioned above.

The black wire is not ground for the fan. It is fan power and supplies +12V which comes in on the green wire. It should be run to the positive terminal on the fan with 10-12AWG wire, and the green wire should also be a heavy gauge wire.

The relay ground is the white wire. When the controller wants to turn on the fan relay, it supplies a ground to the negative side of the coil via the white wire to the relay. You already have power supplied to the positive side of the coil via the ignition keyed line outlined in the instructions.

It sounds like you connected the black power supply line from the relay directly to ground. Perhaps they should have used red wire to eliminate confusion.

Your wiring for the relay (according to the diagram) should be:
White wire from controller, relay coil negative.
Red wire for ignition keyed +12V, relay coil positive.
Large green cable from battery positive post, one side of relay contacts.
Large black cable going to fan positive terminal, other side of relay contacts.
Large cable for fan ground connected directly to battery negative post or car frame.

Also, the relay should be mounted close to the fan. That'll make your main power feed as short as possible.

By the way, considering the "red and green wire coming together" it should still function the same. Since the controller provides the ground, it would not matter if the positive side of the coil had power on it all the time since the controller should turn off when the car turns off. By running the 12V to the coil what you do is also eliminate having 12V on the relay coil all the time so that if the controller somehow failed and kept the negative side of the coil grounded, the relay would not energize so the fan would not run with the car off.

STEINER
Thanks for the response!

I was about to post the same thing about the ground. I spoke to tech support yesterday. It wasnt the black wire that threw me off as much as I read the schematic as saying "fan ground" instead of the correct way.


Do you think 10gauge wire is as big as I will need? I am thinking of starting over with the wiring to avoid confusion and use some/all of the suggestions you posted. Concerning the white (ground) wire..you are saying I should wire that directly to the negative side of the coil INSTEAD OF to the "fan low" on the controller?

You all have been a great help with this, thanks!

STEINER
Thanks for the response!

I was about to post the same thing about the ground. I spoke to tech support yesterday. It wasnt the black wire that threw me off as much as I read the schematic as saying "fan ground" instead of the correct way.


Do you think 10gauge wire is as big as I will need? I am thinking of starting over with the wiring to avoid confusion and use some/all of the suggestions you posted. Concerning the white (ground) wire..you are saying I should wire that directly to the negative side of the coil INSTEAD OF to the "fan low" on the controller?

You all have been a great help with this, thanks!


10AWG is good for 30A at the lowest insulation class. Most fans will draw less than 20A.

The white wire goes from the fan controller to the relay. They're keeping the positive side of the fan relay coil hot all the time so you just need a ground for the coil to energize and close the relay contacts. When the controller says it's time to turn the fan on, it supplies ground on the white line.

That's how I read it going by your instruction sheet.