need mustang help

Vincent Keene · **Posted:** Thu May 07, 2015 2:51 pm

RodneyWright wrote:

The frustrating thing is the car is throwing no codes, so as far as computer is concerned, the car is fine.

Mine was running on 5 cylinders for 2.5 hours and it never threw a code.

I'm convinced the damn CEL is for the government to make money, and keep all the Kraut car owner's wallet lighter.

RickyBeam · **Posted:** Thu May 07, 2015 3:25 pm

Vincent Keene wrote:

RodneyWright wrote:

I'm convinced the damn CEL is for the government to make money, and keep all the Kraut car owner's wallet lighter.

Indeed. The MAF in the bug is mis-reading right now. Guess what the CEL code is? Something to do with the ABS module. WTF does the mass air flow system have to do with ABS??? It takes VW specific tools (thanks Ross Tech) to even see the actual problem. (MAF is reading low -- i.e. dirty; apparently a common problem with K&N air filters.)

DickRasmussen · **Posted:** Thu May 07, 2015 7:24 pm

RodneyWright wrote:

@ Dick and Art.... Where is the PCM power relay?

@ Art... The frustrating thing is the car is throwing no codes, so as far as computer is concerned, the car is fine.

Rodney - Per Google it looks like the PCM power relay is in the same box as the others. Top left in this picture.

http://circuitswiring.com/circuit-diagr ... iagram.jpg

However, now that I've studied the diagram more it appears the pcm power relay must be ok since power for the high fan speed relay coil comes from its contacts.

That seems to leave either a problem with the new low fan speed relay, the inputs to the pcm that trigger the low speed fan, or the wiring between the low fan speed relay and the fan.

Or the fan but you've tested it.

BretLuter · **Posted:** Thu May 07, 2015 7:57 pm

RodneyWright wrote:

Well, the mystery continues. I pulled the fan assembly out of the car. From there I checked the wire bundle running to the fan from the fuse box. Nothing. I put a 12v source on the fan motor and I'll be damned if both speeds don't work. There is nothing burned or melted on the fan assembly that I can see.

This leave me 2 issues to chase down. First is the fan switch wire. Failed to check that while I had the manifold off. Bad move on my part. I guess it comes off again. I'd also like to test the current draw on the fan motor itself. Not sure what I'll find, but be good to know.

If those 2 don't show anything, the only item left is the PCM. So, stupid question. Is the PCU and ECM the same thing? I shudder to think what a new ECU and programing is going to cost me.

Wait- if you put 12v directly to the fan, but it didn't work on high or low, that can't be right. You said it worked when you put the AC on, so the fan works- just not on low speed (right?). I would expect the fan to work on high speed at least when you put 12v to it. Stupid question, but how did you connect power to the fan to test?

I'm really thinking the problem is the low speed resistor, but you have to confirm that voltage is getting sent to the fan or not when it calls for it to come on at low speed.

Chad Culbertson · **Posted:** Thu May 07, 2015 8:49 pm

Pretty sure he meant they did work, the phrasing makes it a bit confusing. It might be a southern thing, lol.

BretLuter · **Posted:** Thu May 07, 2015 9:10 pm

Chad Culbertson wrote:

Pretty sure he meant they did work, the phrasing makes it a bit confusing. It might be a southern thing, lol.

Yeah, I read it a few more times and tried to picture Rodney saying it- I think you're right.

:mrgreen:

RodneyWright · **Posted:** Thu May 07, 2015 11:06 pm

BretLuter wrote:

Chad Culbertson wrote:

Pretty sure he meant they did work, the phrasing makes it a bit confusing. It might be a southern thing, lol.

Yeah, I read it a few more times and tried to picture Rodney saying it- I think you're right.

:mrgreen:

lol.... yeah, misprint. Both speeds DO work. Did some more testing this evening. Had my neighbor come over this evening w/ some test meters. We hooked the fan up to a battery tender set to 12v. He tested the current draw of the motor and both the hi speed and low speed looked good as they stayed in the 5-6 volt draw.

Also took the manifold off yet again and looked at the fan switch connector and the wire loom. I couldn't find any issue or evidence of a burned wire or bad connector. Also tested the continuity of the fan switch pig tail, no issues. Right now I'm too the point of putting everything back together and see what comes of it. I'm completely stumped at this point.

RodneyWright · **Posted:** Fri May 08, 2015 1:30 pm

I'm grasping at straws on this issue now. I've checked everything I know to check and I'm still coming up short on a solution. I've looked at everything under the car that I can physically touch and see and now I've put everything back together again. Still have the same issue, no low speed fan.

One item I wanted to check was the fan switch wiring. There is a wire pigtail from the switch that ties into the wiring harness. The switch has a 2 prong connector. I'm assuming that when the switch get warms enough, it closes the contacts that completes the circuit and starts up the fan. Would I be safe in shorting the wire harness connector to close the circuit and possibly start the fan? Last thing I need to do is inflect more damage.

George Bright · **Posted:** Fri May 08, 2015 6:10 pm

Rodney connect a voltmeter to the DB wire running to the low speed relay from the PCM. With the engine cool but running there should be 12v on the lead. When the engine gets to the point the low speed fan should come on this wire should go to 0V. If it does not then there is probably a problem in the wiring to the PCM or the PCM itself.

To make sure the low speed relay and wiring is good jump this wire to ground and the fan should come on low speed.

RodneyWright · **Posted:** Mon May 11, 2015 9:03 am

I've disassembled the fuse block and there is no evidence of any over heating, no melted posts, nothing I can find.

So getting up to date, I've removed the intake manifold for a 2nd time and looked at the fan switch pigtail and checked it for continuity, all good. I've opened up the wiring split casing as much as I can and looked for burnt wires, found nothing. I've purchased a new relay and swapped it out for the low speed, high speed and PCM relays and rotated the relays w/ in the fuse box. No change.

I've looked at all the wires coming from the fuse box to the fan connector and there are no burnt wires. As stated before, the fan tests good on both high and low speeds.

I did some tests where the pigtail connector for the fan switch connects to the wiring harness. I used a multimeter and I'm getting ~4.5v at the connection point. From there I shorted out the the fan switch harness connector w/ a paper clip to complete the circuit.

I put my multimeter on the ground and low speed wire connector that attaches to the fan. W/ the fan switch shorted, I receive 0 volts at the fan connector.

In referencing Dick's link to the fuse box....

let me ask a dumb question. In regard to the PCM relay, what would happen if I shorted pins 30 & 87 on the fuse box? I'm trying to see if that will give me power at the fan wire connector. Or is that a bad move?

BretLuter · **Posted:** Mon May 11, 2015 11:59 am

Should be no problem bridging terminal 30 to terminal 87, all you'd be doing is bypassing the relay- sending the 12v that *should* be present at 30 to whatever is on the other end of 87, which I'm assuming is the + wire for the low speed fan?

If you're extremely anal about this sort of thing, use a short piece of wire with an inline fuse- otherwise just use a piece of wire, a paperclip or anything conductive that you have handy. FWIW, I've done this move a few thousand times and never used a fuse, and never had anything explode or melt down on me- just use common sense.

DickRasmussen · **Posted:** Mon May 11, 2015 5:27 pm

BretLuter wrote:

Should be no problem bridging terminal 30 to terminal 87, all you'd be doing is bypassing the relay- sending the 12v that *should* be present at 30 to whatever is on the other end of 87, which I'm assuming is the + wire for the low speed fan?

If you're extremely anal about this sort of thing, use a short piece of wire with an inline fuse- otherwise just use a piece of wire, a paperclip or anything conductive that you have handy. FWIW, I've done this move a few thousand times and never used a fuse, and never had anything explode or melt down on me- just use common sense.

We are home. I agree with Brett! Shorting the 30 - 87 terminals on the relevant relays will be fine. Since the fan will draw significant current when starting don't be surprised if there is a spark.

Without reading all the recent posts to refresh my memory on what you have tested, you definitely need to verify that the 12 volts "can" get to the fan windings AND that the ground wire of the fan is actually grounded.

RodneyWright · **Posted:** Mon May 11, 2015 8:13 pm

Taking the advice that I could short the 30/87 posts, I have some updated news. When I shorted the 30/87 terminals on the low speed relay, success! I had power at the fan connection. When I shorted the 30/87 terminals on the PCM relay, I had some interesting clicking, no voltage at the fan connection and the message area for the trip mileage and the odo stated a charging system error. I removed the jumper, turned the key off and then started the car. The message displayed correctly.

So what does that mean, aside from the fact I still have an issue. What is this pointing to?

RodneyWright · **Posted:** Mon May 11, 2015 8:55 pm

So I'm willing to pay some bucks, beer or food for some help here please. Even though I work for Duke Energy, I know very little about electrical circuits and the associated symbols. I've always been in either civil engineering or IT. I can really use a hand here please. Looks like I'm not going to make the autox this weekend due to the current condition of the car.

Anyone? I'm home Thur and Fri this week along w/ this weekend for the most part.

George Bright · **Posted:** Mon May 11, 2015 9:29 pm

RodneyWright wrote:

So I'm willing to pay some bucks, beer or food for some help here please. Even though I work for Duke Energy, I know very little about electrical circuits and the associated symbols. I've always been in either civil engineering or IT. I can really use a hand here please. Looks like I'm not going to make the autox this weekend due to the current condition of the car.

Anyone? I'm home Thur and Fri this week along w/ this weekend for the most part.

I suspect that your ECM has fried it's Low speed fan output. To make sure put a voltmeter between 86 on the low speed fan and ground. You should have 12 volts. Next jumper from 86 on the low speed fan relay to ground. if the relay is good then you should have low speed fan. If the fan does not come on then you have another bad low speed fan relay. If it does then the problem is probably the ECM. $$$

I can help you Thursday or Friday after I get off work which is around 4:00. PM me.

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