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#2480299 - 03/13/12 11:32 PM MFS (Turn Signal/Wiper Switch) testing -by enslow
dRock96Marquis Offline

Posting Addict

Registered: 02/22/05
Posts: 24394
Loc: Maryland
The following article outlines testing of the Multi-function switch found in 1992-2002 models.

The Multi-function switch, or MFS, controls the turn signals and hazard lamps on all 1992+ models, as well as acting as the control switch for the wiper system and the highbeam headlamp switch (front to lock, pull back for "flash to pass" at anytime).
For most years and models, the outer rear brake lamps also pass through the MFS (so they can be switched for turn signal or hazard w/ brake lamps) as well as the front cornering lamps (if applicable)
With all these functions within a single switch assembly, failures can cause issues with several systems. Testing the MFS can rule it out if you develop a problem with any of the circuits mentioned above.

Besides the obvious bulb and connector check, testing the MFS should be the first thing you do if you develop a problem with the turn signals, particularly if only one side or only front / rear is affected.

The following article was authored by enslow, and was originally posted in This thread

At least one of you on this forum have replaced the Multi-Function Switch on your Panther assuming that was the problem, only to find that it wasn't. Here is an article that will help you decide whether to go out and buy a new MFS, clean your existing switch, or take another look at your wiper motor instead.

Symptoms: erractic wiper operation, wipers swipe or park unexpectedly.

Tools needed:
-3/8 or 1/4" ratchet wrench
-3/8 or 1/4" short extension
-10 mm socket
-small crescent wrench
-No. 2 Phillips head screwdriver
-small Allen Key or similar small straight probe
-20T torx driver
-medium-large blade screwdriver
-volt/ohm meter
-alligator clips

Testing the MFS

Remove MFS
1. Disconnect the negative battery terminal.

2. Remove LH and RH trim molding.

3. Remove the 3 upper and 2 lower 10mm bolts from knee bolster cover.

4. Position the tilt steering to the lowest position and remove the tilt lever using a small crescent wrench.

5. Remove the 4 shroud screws with a No. 2 Phillips head screwdriver.

6. Remove the lower shroud.

7. Remove the lock cylinder. Turn the ignition to Run, insert the Allen Key or probe as indicated in the image, the wiggle and pull the lock cylinder straight out.

8. Remove the upper shroud. Place the gear shift to D or 1, wiggle the upper shroud from the left side. Return the shift lever to P and remove the upper shroud.

9. Remove the 2 20T screws from the MFS.

10. Remove the 2 electrical connectors using the large blade screwdriver. There are lock tabs on both sides of these connectors. Don't force them out all at once or you can break the lock tabs.

Resistance checks for the Multi-Function Switch:

Refer to image below for the following resistance checks.
1. Wiper switch resistance check:
Terminals 589 and 993

Position_______Resistance (k ohm)
HI____________0 (closed circuit)

2. Interval Resistance check:
Terminals 590 and 993

Resistance (k ohm)
103.3 (longest delay position)
3.3 (shortest delay)

Check to see the resistances do not spike as you wiggle the switch in any of position.

If resistances are within 5 about ohms and they regularly decrease from longest to shortest delay, the switch is probably good.

If you see spikes as you wiggle the rotary interval switch, you could try cleaning the contacts. I'll post a procedure for cleaning those contacts later.

If resistances indicate open circuits (very high resistances) or closed circuits where there shouldn't be any, you could try dissembling the entire switch body and locating the damaged wires. It is possible, but you will need a lot of patience! I've got images of that repair also, but I don't know if anyone would be interested in it.

--------Courtesy enslow
-Panther info & FAQs-

Former owner of a Grand Marquis with a few mods, Grand Marquis "LSE S/C"

#2480309 - 03/13/12 11:43 PM 03+ MFS (Turn Signal/Wiper Switch) testing [Re: dRock96Marquis]
dRock96Marquis Offline

Posting Addict

Registered: 02/22/05
Posts: 24394
Loc: Maryland
Below are the pinouts and testing information for the 2003+ style MFS. While the turn signal/hazard section of the switch is relatively unchanged, the wiper control functions are much different and no longer resistance based. The wiper control module was eliminated with 2003, with all its functions integrated to the wiper motor assembly.

Clicking the images below will load the fullsize version

Additional related lighting circuit diagrams can be found here;

And related body wiring (including wipers) here;

Edited by dRock96Marquis (03/13/12 11:47 PM)
-Panther info & FAQs-

Former owner of a Grand Marquis with a few mods, Grand Marquis "LSE S/C"


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