need mustang help

RodneyWright · **Posted:** Mon May 11, 2015 9:56 pm

George Bright wrote:

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.

Thanks for the input George, greatly appreciated! I tried to do what you suggested in the previous post w/ looking at the DB wire from the PCM. Problem is I can't find a DB wire coming from the PCM. I've found a DB wire, but it's coming from the direction of the fan switch. I'll put the volt meter on the 86 and ground and report back.

So reading your text above, do I need to leave the relay in place or remove it when I test? I'm assuming I need to remove the relay and jumper the ports on the fuse block.

BretLuter · **Posted:** Mon May 11, 2015 10:03 pm

RodneyWright wrote:

George Bright wrote:

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.

Thanks for the input George, greatly appreciated! I tried to do what you suggested in the previous post w/ looking at the DB wire from the PCM. Problem is I can't find a DB wire coming from the PCM. I've found a DB wire, but it's coming from the direction of the fan switch. I'll put the volt meter on the 86 and ground and report back.

So reading your text above, do I need to leave the relay in place or remove it when I test? I'm assuming I need to remove the relay and jumper the ports on the fuse block.

You want to pull the low speed fan relay and put the meter on terminal 86 of the relay plug (not the relay) and ground, checking to see if you get 12v (with the key in the "on" position)- this is with the low speed fan switch contacts or connector jumpered to simulate the switch being closed, calling for the fan to come on at low speed.

DickRasmussen · **Posted:** Mon May 11, 2015 10:11 pm

Rodney -

Here is some info from the 2012 5.0 service manual:

Quote:

Cooling Fan Control
The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C ON/OFF status, A/C pressure) to determine engine cooling fan needs.

The fan controller has the capability to detect certain failure modes within the fan motors. Under certain failure modes, such as a motor that is drawing excessive current, the fan controller shuts OFF the fans. Fan motor concerns may not set a specific DTC.

With the fan motor disconnected from the fan controller, voltage may not be present at the fan controller.

For Mustang, F-150, Navigator, Expedition, Escape, Transit Connect, relay controlled fans:
The PCM controls the fan operation through the fan control (FC), (single speed fan applications), low fan control (LFC) and high fan control (HFC) outputs. Some applications have the xFC circuit wired to 2 separate relays.

For 2-speed fans, although the PCM output circuits are called low and high fan control, cooling fan speed is controlled by a combination of these outputs. Refer to the following tables.

MUSTANG: PCM FC OUTPUT STATE FOR COOLING FAN SPEEDS

PCM OUTPUT LOW SPEED HIGH SPEED FAN OFF
LFC ON OFF OFF
HFC OFF ON OFF

RodneyWright · **Posted:** Tue May 12, 2015 8:40 am

I've put everything back together and tested terminal 86 of the low speed fan relay and I do indeed get 12v according to the volt meter. George, if I read your text right, you think the issue is w/ the ECU if I DID get 12v? That's going to be some serious bucks....

I guess my next step is to pull the ECU or PCU and look inside it. Fingers crossed. Just stands to reason w/ my recent track record on this car that the most expensive item craps out on me....

RodneyWright · **Posted:** Tue May 12, 2015 8:45 am

BretLuter wrote:

You want to pull the low speed fan relay and put the meter on terminal 86 of the relay plug (not the relay) and ground, checking to see if you get 12v (with the key in the "on" position)- this is with the low speed fan switch contacts or connector jumpered to simulate the switch being closed, calling for the fan to come on at low speed.

Bret, I'm assuming what you mean above is to jumper 30 & 87, which I've done. When the low speed fan relay terminals 30 & 87 are jumpered, I do get 12v at the fan connection.

DickRasmussen · **Posted:** Tue May 12, 2015 9:41 am

RodneyWright wrote:

BretLuter wrote:

You want to pull the low speed fan relay and put the meter on terminal 86 of the relay plug (not the relay) and ground, checking to see if you get 12v (with the key in the "on" position)- this is with the low speed fan switch contacts or connector jumpered to simulate the switch being closed, calling for the fan to come on at low speed.

Bret, I'm assuming what you mean above is to jumper 30 & 87, which I've done. When the low speed fan relay terminals 30 & 87 are jumpered, I do get 12v at the fan connection.

The only thing I can think of now is to ground the PCM side of the low speed relay coil with the key on. This would simulate the PCM doing the same thing. This should cause the low speed relay contacts to close. Per the posted diagram it is pin 86 (per the shop manual for my 2012 it is pin 85). To verify that pin 86 is correct for your car, check the voltage at pin 86 and 85 of the socket with the relay removed. If 86 has zero volts and 85 has about 12 volts then I'm pretty sure 86 is the pin to jumper to ground after replacing the relay.

I would disconnect the wire to the PCM (C11 apparently) first unless someone who has more experience knows better.

If grounding the relay coil pin 86 works then it looks to me like a trip to a dealer is appropriate. They have scan/diagnostic tools plus, hopefully, experience to go directly to the real problem.

RodneyWright · **Posted:** Tue May 12, 2015 10:46 am

DickRasmussen wrote:

The only thing I can think of now is to ground the PCM side of the low speed relay coil with the key on. This would simulate the PCM doing the same thing. This should cause the low speed relay contacts to close. Per the posted diagram it is pin 86 (per the shop manual for my 2012 it is pin 85). To verify that pin 86 is correct for your car, check the voltage at pin 86 and 85 of the socket with the relay removed. If 86 has zero volts and 85 has about 12 volts then I'm pretty sure 86 is the pin to jumper to ground after replacing the relay.

I would disconnect the wire to the PCM (C11 apparently) first unless someone who has more experience knows better.

If grounding the relay coil pin 86 works then it looks to me like a trip to a dealer is appropriate. They have scan/diagnostic tools plus, hopefully, experience to go directly to the real problem.

As noted above, I get 12v when I check terminal 86 of the low speed relay to ground. I have not checked terminal 85. I don't think referencing your 2012 manual is doing me much good since you've stated some differences in the terminals and power, but I do appreciate the help in trying to chase this issue down.

Taking this to the dealer is the LAST thing I want to do. My car gets sucked up into some void, they don't talk to me to ask what I've checked because car owners are stupid and they charge me WAY too much money. If someone has a knowledge of a GOOD and REPUTABLE mechanic and trusts them, I'd consider it, but I'd rather battle this out some more and learn from this. I will say between the diff and this electrical issue, once fixed, this car is dangerously close to being traded in....

In regard to the ECU or PCM, this beast is sealed tight since it's exposed to the elements. I hesitate to break this open only to find no issues. I'd like to positively chase this down to something that's causing the low speed fan not to work. If it takes me a month, so be it....

Vincent Keene · **Posted:** Tue May 12, 2015 11:41 am

RodneyWright wrote:

Taking this to the dealer is the LAST thing I want to do. My car gets sucked up into some void, they don't talk to me to ask what I've checked because car owners are stupid and they charge me WAY too much money.

No good mechanic will trust the owner's diagnostics. They will all start at square one and work from there. If they take your word that you checked X & Y, so they start at Z, what happens when the problem was actually X? Should they charge you for the time they spent extra just to go back to the beginning?

RodneyWright · **Posted:** Tue May 12, 2015 12:26 pm

diving deeper....

After closer inspection of the BEC or fuse box layout, it looks like terminals 85-86 are flip flopped between the high speed and low speed relays. I was only looking at the bottom of the relay for the markings, so I gave bad info before.

In retesting the low speed 85-86 terminals, 85 gives a 12v reading grounded w/ the key on. Interesting enough 86 measures .02v. What does this corrected info mean?

RodneyWright · **Posted:** Tue May 12, 2015 12:32 pm

Vincent Keene wrote:

No good mechanic will trust the owner's diagnostics. They will all start at square one and work from there. If they take your word that you checked X & Y, so they start at Z, what happens when the problem was actually X? Should they charge you for the time they spent extra just to go back to the beginning?

as they probably should, but at least talk to me and ask what I've done. You have a good mustang person to recommend?

DickRasmussen · **Posted:** Tue May 12, 2015 12:47 pm

RodneyWright wrote:

diving deeper....

After closer inspection of the BEC or fuse box layout, it looks like terminals 85-86 are flip flopped between the high speed and low speed relays. I was only looking at the bottom of the relay for the markings, so I gave bad info before.

In retesting the low speed 85-86 terminals, 85 gives a 12v reading grounded w/ the key on. Interesting enough 86 measures .02v. What does this corrected info mean?

Rodney - Were those readings with the low speed relay out of the socket but with ignition on? If so that is what I expect is "correct". .02 volts is essentially "zero" in this situation due to meter calibration and maybe a little bit of "above zero volts" from the PCM.

I'm not sure whether the PCM is supposed to connect pin 86 to ground with the ignition on but the engine not running.

Can you disconnect the wire between pin 86 and the PCM? If so, with the relay in the socket try applying chassis ground to the connector that the contact that you removed the PCM wire from with ignition on. The relay "should" then apply power to the fan. I'm reluctant to suggest applying ground to 86 with the PCM connection intact even though my "guess" is that ground won't hurt the PCM. I just don't know enough to be sure and I wouldn't risk my $$$ let alone yours.

Regarding dealers, The main service department of Capital Ford diagnosed an emissions vapor recovery problem check engine code on our 97 first time at what I thought was a reasonable price.

However, if you have the time for the drive, Contact Michael Sperber owner of Asheboro Ford http://asheboroford.net/
and see if you can work out a logistically acceptable way to get his guys to work on the problem. Michael is a racer (last year SARRC ITA champion I think) and is happy to do what he can for other racers (including autocrossers).

If you cannot easily get him on the phone, PM me and I'll give you his email address.

Remember even if you have to spend even a $1000 for diagnostics and a new PCM the cost of trading to something else and setting it up will be much more IF you otherwise would like to keep this car. :wink:

DickRasmussen · **Posted:** Tue May 12, 2015 12:51 pm

I didn't make it clear in my previous post but Michael Sperber and his team WILL at least listen to what you as a racer and DIY guy have done already. I worked directly with his lead tech on the 2015 strut/camber modification to make sure he understood exactly what I needed after I was too whimpy to drive the splined bolts out of the spindle.

Chris Halweg · **Posted:** Tue May 12, 2015 12:51 pm

I have nothing useful to add, but I commend you for your heroic effort thus far.

RodneyWright · **Posted:** Tue May 12, 2015 1:15 pm

DickRasmussen wrote:

I didn't make it clear in my previous post but Michael Sperber and his team WILL at least listen to what you as a racer and DIY guy have done already. I worked directly with his lead tech on the 2015 strut/camber modification to make sure he understood exactly what I needed after I was too whimpy to drive the splined bolts out of the spindle.

Thanks Dick.... I'm hoping not to have to drive that far. I need to investigate if I have any option over at crossroads since they support the mustang club. I'm hoping to make the meeting this Thursday evening so I can get some insider info if possible.

DickRasmussen · **Posted:** Tue May 12, 2015 1:18 pm

Rodney - Regarding a good local mechanic we had VERY good luck with Adam of On-Site Automotive (919) 758-9960. He comes to YOU at home (or at the office if parking allows of course). Adam has a ton of experience with a lot of vehicles but I don't know if he has the specific experience or diagnostic tools for you car. We used him for the van and for A/C on the 97 Mustang. Since I was retired by then I simply watched and kibitzed and gave him whatever info I could.

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