Trying to find whats wrong with my old Fem

[HKS]

Hi Volker
on what page did you make that diagram i cant find it
/Fredrik

Page 71-1

It looks like Q36 may not be using PWM mode. Looks like a simple (P channel MOSFET), on off switch. Overloaded maybe.
Hermann

[Fredrik73]

Page 71-1

It looks like Q36 may not be using PWM mode. Looks like a simple (P channel MOSFET), on off switch. Overloaded maybe.
Hermann

Thank you Hermann.
soon i will go on and measure on my fem
has bin alot at work and home now
hope every thing is fine
/From Fredrik

[Fredrik73]

Page 71-1

It looks like Q36 may not be using PWM mode. Looks like a simple (P channel MOSFET), on off switch. Overloaded maybe.
Hermann

ooohh nooo
i miss the pages between 71-2 to 81-2
maby thats why i did not found it
can you Hermann please send them as PDF to me so i can print them out and put in my Book
or just take photos and send them?
/Fredrik

[HKS]

ooohh nooo
i miss the pages between 71-2 to 81-2
maby thats why i did not found it
can you Hermann please send them as PDF to me so i can print them out and put in my Book
or just take photos and send them?
/Fredrik

Do you have 71-1

[Fredrik73]

Do you have 71-1

Yes i have

[Fredrik73]

Hmm i must have bin sleeping you Said 71-1 before and i did not find it but i have it
sorry

[Fredrik73]

sorry for not writing, but im waiting for the relays from China
must have shosen deliver by bicycle so maby they soon are In Tibet hihihiih

[Fredrik73]

have bin focusing to get the car ready for inspection so the Fem has laying on the shelf for a while

[Old Red Car]

This is primarily for Herman, I have been amazed at your detailed expertise on the FEM. My bird has stiff steering at low speed. No other problems. I have two questions:
First, is the steering control a gate switch? I thought most MOSFET's are on off...if so, how would the power steering control vary based on speed?

I guess I am up to three questions now. How can I diagnose if the power steering issue is the FEM without replacing the module? I see no way I could take is apart like you and Fredrik without making a mess.

Thanks,

Bill

[HKS]

Bill,
Most likely it is Q35, a P channel power MOSFET.
it is not just on and off. It is continually switched on and off. PWM pulse with modulation. And therefore produces a lot of heat and a short life.

Marginal design. Needs better cooling/heat dissipation.
Ford will charge for checking all wires first and then tell you no FEM IN STOCK.
If you can get one, do it now.
Hermann
P.S. Better P Mosfets may be available.

If you have a 2003-5 Tbird, buy one on Ebay.

Edit: PWM is used to vary the Power Steering assistance relative to speed. There is an actuator on the power steering pump.
The most power steering assist should be when you are parking or driving slow.

[Fredrik73]

This is primarily for Herman, I have been amazed at your detailed expertise on the FEM. My bird has stiff steering at low speed. No other problems. I have two questions:
First, is the steering control a gate switch? I thought most MOSFET's are on off...if so, how would the power steering control vary based on speed?

I guess I am up to three questions now. How can I diagnose if the power steering issue is the FEM without replacing the module? I see no way I could take is apart like you and Fredrik without making a mess.

Thanks,

Bill

Yes i troubleshoted for a verry long time With out result i did not wanted to buy a FEM but at the end i had to (and the price dont go down for that part)
/Fredrik

[HKS]

There are 3 FEMs for sale on Ebay that work for tbirds 2003 2004 and 2005.
Zero for 2002.

[njtwombly]

sorry for not writing, but im waiting for the relays from China
must have shosen deliver by bicycle so maby they soon are In Tibet hihihiih

Hi Fredrik- Did you ever find a suitable replacement for the Omron relay(s)?

[Fredrik73]

Hi Fredrik- Did you ever find a suitable replacement for the Omron relay(s)?

Hi Nick yes i think so
i have not tested it but it looks right
i can post photos
best regards Fredrik

[flip]

I know this is my first post as well as reviving a necro-thread but wanted to put in my .02. I am a Ford dealer and have a relatives 2002 bird in for the cluster light issue, did a bunch of searches and found this forum and specific thread. I have repaired clusters, displays, radios and other minor things before and felt a FEM was worth at least taking apart to see if anything let the magic smoke out.

Just poking around Q36 nothing really tested "bad" so I flipped over and started checking the other surface mount resistors. R236, which appear to feed the center leg of Q36 was a complete open circuit. I didn't take a pic of the resistor prior to removing but It was a 6192is which was essentially 62K ohm 0805 series. I was unable to find the 5101 P transistor but had ordered a few things ahead of time just in case. Replaced the resistor, plugged in and dash lights worked. The resistor did not have any visible defects when it was removed and it's possible it failed due to some other factor and will fail again.

Felt like this was worth sharing as it may help someone else in the future and would also like to know why it's nearly impossible to find the 5101GF transistor or some other P channel alternate.




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