need mustang help

DickRasmussen · **Posted:** Tue May 05, 2015 8:53 pm

Rodney -

Do you have a manual or other document that shows the wiring diagram for the fan(s) and how many relays/fuses?

Did you say whether the fuse box side of the fan control relays has 12 volts either all the time or at least when the engine is running?

Have you checked continuity/resistance through the fan motor(s)? If one motor and 3 terminals then check pairs since one winding may be shorted or open.

If "melting" that implies a short initially that may have burned open before blowing fuses (shouldn't but ???).

FYI we aren't home so I cannot look at the manuals for our 97 or 12 GT's but the 15 manual I do have shows 2 fans and 3 control relays and about 4 fuses due to the way the 2 fans appear to be able to work individually or together.

The relays are controlled from the PCM.

DickRasmussen · **Posted:** Tue May 05, 2015 9:02 pm

Rodney - When the fan motor bearing(s) started going bad on our 97 a few years ago I got a Dorman replacement from Advance Auto. It took 2 tries to get one that wasn't out of balance but the price was much better than oem Ford. If now though I would try Crossroads Cary ONLINE first and then Rock Auto for oem Ford. If Dorman is the best price however I would buy local for faster "return/replace" if defective.

Crossroads Ford Online has better prices than the Capital Ford THSCC discount due to their huge buying power (lots of dealerships) but also has the advantage of local pickup.

RodneyWright · **Posted:** Tue May 05, 2015 9:25 pm

@ Dick.... I'm not very schooled at reading electrical diagrams, so I'd need some assistance by someone that knows what they're doing. Symbols on the diagram don't relate to what I'm actually looking at.

RodneyWright · **Posted:** Tue May 05, 2015 9:34 pm

so there's this....

http://iihs.net/fsm/?dir=40&viewfile=Cooling%20Fan.pdf

not exactly sure how to read this or what to check. If someone can give me some decent guidance, I'd appreciate the pointer in the right direction....

BretLuter · **Posted:** Tue May 05, 2015 9:34 pm

can you scan and post a pic of the fan wiring diagram?

BretLuter · **Posted:** Tue May 05, 2015 9:37 pm

Found this suggestion on a Mustang forum, same year car:
(my bet is on the low speed resistor)

The following assumes the fuses and relays are good, per your initial post.

Start the engine, and turn on the A/C.
If the fan runs, then the fan motor, and the high speed circuitry components are good.

If the fan does not run when the A/C is turned on, then either the fan motor is bad, a high speed wire is bad, a high speed connection is bad/loose, a high speed component in the PCM is bad, or a high speed component inside the wiring harness connector on the side of the fan shroud is burned/melted.

If the fan runs when the A/C is turned on, then turn off the A/C, and keep the engine running. If it starts overheating and the fan does not turn on at low speed, then either the low speed resistor is bad(located inside the fan shroud), the cylinder head temperature sensor is bad, a low speed wire is bad, a low speed connection is bad/loose, a low speed component in the PCM is bad, or a low speed component inside the the wiring harness connector on the side of the fan shroud is burned/melted.

To check for burning in the wiring harness connector on the side of the fan shroud, disconnect the battery's negative cable, and disconnect the wiring harness connector on the fan shroud. If something is burned, then one solution is to replace the connector assembly.

BretLuter · **Posted:** Tue May 05, 2015 9:47 pm

andddddddd, here's a wiring diagram:

http://iihs.net/fsm/?dir=40&viewfile=Cooling%20Fan.pdf

Take your trusty meter, and with the car at "normal" operating temp, check for power at the plug going to the electric fan between the LG-YE (Light Green/Yellow?) wire and ground. If you're sure it's up to temp and you don't have power here, then there's a problem before the fan (i.e. NOT the low speed resistor), if you have power there, but the fan doesn't come on, then the resistor is bad.

At least that's how I interpret the wiring diagram.

EDIT: and another forum thread with more info on how to troubleshoot the resistor and other possible issues- http://www.allfordmustangs.com/forums/2 ... ing-2.html

DickRasmussen · **Posted:** Tue May 05, 2015 10:03 pm

RodneyWright wrote:

@ Dick.... I'm not very schooled at reading electrical diagrams, so I'd need some assistance by someone that knows what they're doing. Symbols on the diagram don't relate to what I'm actually looking at.

Rodney -

Basically what Bret said. However before testing with the engine running I would use an ohm meter to check winding/resistor resistance to look for the resistor being "open". Disconnect (label first of course) the 3 wires at the motor. Then check resistance between the terminal that had the lg-ye wire and the one that had the bk (ground) wire. Then repeat for the lg-vt and bk pair. If it is low speed that doesn't work then lg-ye to bk probably will read "open".

Dick

RodneyWright · **Posted:** Tue May 05, 2015 11:13 pm

thank you! Gives me something to chase tomorrow evening....

George Bright · **Posted:** Wed May 06, 2015 5:06 pm

Like Brett said let it warm up some and check for power at the LG-YE wire. If the motor is like a Taurus fan motor it has two windings and not a resistor. If there is power on this wire and the fan is not running then the low speed winding is bad. If you cannot get a fan motor in time then you could splice the GT-Ye wire from the relay to the LG-VT wire. Then the fan would run on high speed when either speed is called for. That would keep it from getting hot before the fan comes on.

I gather you have already replaced the low speed relay. The only other thing would probably be a problem with the ECU. that would probably be expensive.

RodneyWright · **Posted:** Wed May 06, 2015 10:19 pm

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.

DickRasmussen · **Posted:** Wed May 06, 2015 10:43 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.

Rodney - I think PCM (Powetrain Control Unit) is Ford's terminology for ECU.

Have you checked or replaced the PCM Power Relay which is in series with the coil of the low speed fan relay?

DickRasmussen · **Posted:** Wed May 06, 2015 10:53 pm

Rodney - Also before pulling the manifold can you jumper 12 volts to the fan side terminal of the low speed relay socket or whatever is accessible on the fan side of the relay?

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

Been away from the forum for a few days. Took a look through the "Engine Cooling" section of my 2007 Helms manual and didn't find much to help your situation other than these Powertrain Control Module Diagnostic Trouble Codes found on page 303-03A-6:

P0480 - Low Fan Control (LFC)/Fan Control 1 (FC1) Primary Circuit Malfunction - see the Powertrain Control/Emissions Diagnosis manual (which I don't have)

P0481 - High Fan control (HFC)/Fan Control 3 (FC3) Primary Circuit Malfunction - see the Powertrain Control/Emissions Diagnosis manual (which I still don't have)

I did learn that my car has a generator (since when did we stop using alternators?), and that the generator has to be removed to change the thermostat. Also learned that the generator has a clutch to disengage it during sudden engine deceleration.

Regarding getting parts through Crossroads: I used the online ordering once and thought the discount was pretty good. Dave O says to call the parts manager (he can give you the name) and ask for the HCMC discount.

RodneyWright · **Posted:** Thu May 07, 2015 2:47 pm

@ 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.

THSCC Forums

need mustang help

Who is online