1991 F-150- 4.9l, M5od. Tilt Steering.

Earlier this week the right turn signal began to stay lit steadily. The left turn signal lights as it should, but it deactivates the cruise control. Otherwise left turn signal and cruise control work well. Any ideas?

 

bump ,,,,,,,,

 

The right turn is the one that lights up but doesn't flash, the left does and its the one that cancels cruise?

 

Right. And BTW what I meant is that the left signal CANCELS the cruise- If I want to reset it, I don't have to turn it on again, just use the SET or RES key.

 

hmm I'm interested in the cause of this myself my 87 F150 did this too. Is this the result of a short??? or perhaps a preset response to an open circuit such as a bad or improperly seated bulb???

 

Sounds like a short circuit in the multifunction switch, left turn is simulating hitting the brakes canceling cruise but not turning it off.

I briefly looked over the diagram before my first post here, see if that was in anyway possible, didn't spot it right off but I do know the MFS's can and do do strange things when they die.

Rather then chase it down on paper, checking for every possible cross circuit that might occur, probably prove faster to remove the MFS, unplug it it from its harness connector, use a jumper wire and test each circuit verifying they all work correctly without it.

If it does it shows the switch as the cause of the problem, if not you know to look elsewhere.

 

Sounds like a good analysis. Now I'm curious if the brake lights come on when the LH signal does. I know that taking the turn signal switch out is super easy, so I'll take it out and test it. While I'm in there I'll check up on the emergency fix I made to the key tumbler rack & pinion, that's been in there for 2 years, probably over 2500 starts now, and is a time bomb. I'll let everyone know what I found after I get the switch out on Sunday.

Edit: I don't realize if this is what you meant or not, but I don't have a multifunction switch. It just controls the blinkers, and the stalk on the outside also pries up the tilt steering latch. If the truck was made 9 months later it would've had a MFS. Anyway, I too suspect the switch is no good and will be carefully examining it since I know it's just a flimsy piece of plastic.

 

I don't realize if this is what you meant or not, but I don't have a multifunction switch. It just controls the blinkers, and the stalk on the outside also pries up the tilt steering latch.

Hmm my book shows it as a MFS however now I gotta better idea what one you do have.
Probably not in the switch itself then, sounds like its probably in the harness running down inside the column. Wires worn through making contact with each other where they shouldn't be. Or possibly out under the hood near the firewall, at a harness connector where the wires enter/exit it, wires bare back from it where the casing has corroded away allowing some of them to contact each other. I lean toward the wires in the column at this point though.

 

Last night I went to Wal-Mart and got the bulbs for the turn signal and installed them in the parking lot. On the way home my turn signals and cruise control worked perfectly. I don't understand how the cruise is affected by a burned-out bulb, but I'm going with it.

In any event, I lied. Today is Sunday and I did not remove the steering wheel to examine the cruise and blinker switches as I promised I would. They work now and I'll wait 'til they break on their own, before I go trying to break them myself.

Some FTE members have said that any problem that can't be fixed with a hammer is an electrical problem. I disagree. There are several electrical problems my truck has had that I've solved with a hammer, because it has a completely unorthodox, mostly aftermarket, electrical system that defies any wiring diagram I've ever seen. PO worked on it himself, but knew nothing about autos and did some crazy stuff.

 

Yes this is always caused by bad bulbs.