Man what kind of tool do I need to get the steering column shrouds off???? The two torx screws on the bottom no problem, but there a bunch of very recessed hex head screws up in there from the bottom and a very tight diameter hole to try to get any kind of socket in there.... am I missing something???

thanks for that switch PDF.... Haynes has something similar but not as good!!

 

So I take it I’m looking for 12v at B1 and B2 to see if the harness is good, correct?

 

B1 and B2 should have 12V going in; depending on the switch positions as to which ones should have 12V going out.

You may also see 12V on M2, the yellow one, since it'll be fed from the dome light.

As to the shroud - I dunno, my 1988 doesn't have the shroud. I'd bet there's torx bits up in there also. But I don't know.

Well, there's always a later year manual to check ... the 1995, which is also available from here for a download (link is in the FAQ message, about 40% of the way down - do yourself a favor, grab all the parts lists also!)

The 1991 may be different, but there's a start.

RwP

 

Well my day got toasted just getting the steering column housing apart. Here the screws are simply the same T15 as the bottom screws. You just need a long T handle to get in there. I feel so dumb. Oh well. Anyway...

I got the multifunction switch out and I tested for continuity. Thank you Ralph for your posts, and the rest of you guys, before I forget to say that...!

I looked at Ralph's pinout and the Haynes book. I did find that jiggling the turn signal arm did result in a couple of points that should not have continuity would be intermittent! Not always repeatable though and sometimes it did look like it was functioning okay.

Tomorrow I'm going to check the harnesses and main headlight switch for voltages.

 

OK all, I have an update:



Both headlamps disconnected, I have continuity to ground on both outside pins, NOT on center pin. Battery disconnected and multifunction switch is disconnected.

Both headlamps disconnected, I have continuity to ground on both outside pins, NOT on center pin. Battery disconnected and multifunction switch is disconnected.

Testing pin 19 of multifunction switch. Battery Connected. Common test lead grounded at steering column. With headlight switch OFF, no voltage, no continuity to ground. With headlight switch ON, no voltage, but I get continuity to ground!!!!

Soooo now what??? That does not seem right to me at all!!!!
I guess now I need to go back to the headlight switch and connector for the harness there...

 

You may be getting continuity to ground through other items on the circuit when the headlight switch is on.

I don't know why you're measuring continuity with the battery connected - it's a great way to destroy a meter! (I.E., don't do ANY resistance measurements with power applied. None. Zip. Zero. Nada. I tried that once accidently; the meter jumped a foot as it blew the fuse and the meter ... learned MY lesson!)

Either measure voltage with the battery connected, or continuity with it disconnected; don't mix.

Now.

Time to check the continuity from there to the connector on the headlight switch with the power off.

But.

If you've got high beams, and not just Flash To Pass, that's all good.

Time to check continuity between the low and high beam outputs alternatively and the headlight in (i.e., common in headlight into the switch; check low beam output for continuity, then check high beam output for continuity.)

Did you check for VOLTAGE at the front, using the wire colors I provided? Don't check continuity; we're not looking for that!

RwP

 

Okay, so a Eureka moment! Sort of...

I believe my headlight switch is bad. Tested terminal B1 on the headlight switch harness with battery connected. Good 12V, no short to ground!. Tested the P and H feedlines from that switch to the corresponding multifunction switch pins. Good isolated continuity, no shorting to ground or elsewhere!

But I think there is bad news:

Can someone tell me the proper pinout at the headlight sockets? Which pin is supposed to be ground, low, and high?? They are 3 pin connectors. Battery connected, both headlight and multifunction switch pulled out of truck:

Both outside pins are 525 ohms to ground.
Center pin no continuity to ground.

That does not look right to me!!

I feel that if there is a problem here, that took out the switch...

Ideas?

 

Digesting what you wrote Ralph...

 

I don't know why you insist on continuity tests!!!

DON'T!!!!

You will succeed only in totally confusing yourself. Especially if you pick the wrong place to check against.

Now.

Do you have 9004, or 9007, bulbs in the headlight? They use the same connector but wire differently.

Presuming 9004 - the wiring is violet/white low, red/orange high, the remainder wire ground. (Same colors for 9007, but they pin out differently.)

Shucks, your problem MAY be someone's used the wrong bulbs ... which ones do you have?

See for instance https://sparksmith.com/blogs/news/do...and-9007-bulbs for an explanation.

See also the attached PDF; it shows the colors leaving the MFS going to the front.

RwP

 

I'm doing a combination of continuity tests and voltage tests. I only did one continuity test with the battery connected (as you caught earlier)!

Shouldn't I have continuity between ground and one of the pins at each headlight? Will report back on which headlights I have in a sec!