My cruise control works fine until I turn the headlights on then it shuts off. Do any of you gurus know where to look? Thanks. '94 XLT

 

I see you don't have any replies yet, so I'll see if I can get things started.
Lots of unknowns. Is this an after market cruise control, or Factory, or Dealer, or User installed OEM system & is the vehicle manual or auto tranny?
Did the problem come about suddenly after some event?
Use, or come by the ELM scan tool & running diagnostic freeware FORScan (that's tweaked for Fords), on the viewing device of your choice as discussed here https://www.ford-trucks.com/forums/1...-scantool.html, as it can access All of the vehicle computer/controllers & have it scan the vehicle computer/controllers for trouble code clues & post All code Numbers, as they can help focus a trouble shoot.

 

Factory cruise control, A4LD trans and 4.0 engine. XLT, OBD 1. I'll have to get the codes from the "check engine" lights. The light has been on for a while but goes off and then back on. Truck runs fine except for occasionally it'll seem to shut off, like turning the key off, for an instant then pick up and run good. Over 200K with nothing internally done to the engine. Last year the "check engine" light was on and I had to replace some blown capacitors in the ECM and both O2 sensors. All the codes were clear then.

 

WOOOPS, I missed the end of your initial post that said it was a 94, so your right that it's OBD-1 & the ELM won't work with OBD-1 so dismiss my suggestion to try & scan your 94 with one. The ELM works really good with OBD-2 though, so if you turn wrenches on OBD-2 or later vehicles the ELM & FORScan are fine tools for our electronic tool box.

Good feedback on the vehicle & past woes with it. Since this is OBD-1 you have several ways to scan for trouble code clues by using a code reader, or following one of these hookup pictorials, http://www.troublecodes.net/ford/ & watch the in dash CEL, or test lamp, or analog meter needle blink/wave the codes, then post up All code Numbers, as they can sometimes help focus a trouble shoot.,

 

I'll read the codes ASAP, right now I'm going fishing.

 

House needs painting, grass needs mowing, truck needs fixing.....Gone Fishing!!!! At least you have the Priorities in order!!!! lol
My Bass Tracker batteries were all charged up, new tank of gas, yet things got so crazy here with me having to fill in on sudden family members medical problems that I never got to wet a danged hook at all last year, first time in 20 years & its Still crazy here, but I'm determined to stay focused get my family member fishing buddies healed up good enough to drown some bait this year, even if its artificial bait & yes we can fish hard enough to drown artificial bait!!!! lol

Back to the cruise control, since it's a OBD-1 vehicle & OBD-1 isn't as advanced as OBD-2 diagnostics, it may take longer to home in on the problem but hang in there on your trouble shoot, don't despair, with good feedback the forum can likely help think the problem/s through.

Are you having any speed-o irregularities, like the needle jumping around, or the cruise control dropping out, or not wanting to take a set, or the tranny shifting acting out, or the anti-lock brake system acting out?

EDIT: Forgot to ask if the battery cables are in good condition & the connections on Both ends are clean, bright & tight, especially the battery B- connections to engine & body & the clamps to battery posts.

 

 

I changed to LED bulbs in the tail lights a couple of weeks ago. That might be the problem. Unfortunetly I discarded the incandescent bulbs so I can't try it.

 

Did the problem begin immediately after you installed the LED brake lamps?

 

Not sure. I'm an old fart and rarely drive at night.

 

Ok, well then was the problem present when the incandescent lamps were in place?

 

Being as I don't drive at night I don't remember. I think I'll remove the bulbs and try it.