Hello,
I have a 86 F150 with the EFI 302, hopefully someone can help me out. For some reason sometimes the headlights just dim by themselves, sometimes to the point I can't see and sometimes won't come back to full light until I trun the truck off and on again. Is it a regulator problem?

I was also wondering if there is a way to turn the idle down, when I first start the truck it revs up pretty high until its warmed up, is there any way to adjust this?
Any help would be appreciated

 

If the battery is charging and the truck is restarting, it likely isn't a regulator problem. These trucks are known for having several problems that will contribute to dim headlights. One is the inherent design of the headlight system that runs power from the battery, through the headlight switch, and back to the lights. This causes both a huge voltage drop and excessive heat and wear in the headlight switch. There is a relay upgrade that can fix both those problems.

Second, the 2G alternators on these trucks are barely sufficient to meet the minimum power needs for these trucks. To make matters worse, on your truck you have two 10AWG wires that come off the alternator and turn into one 10AWG wire in the harness leading to the hot stud on the starter relay. Odds are this junction where the two wires turn into one is worn and probably pretty close to the breaking point. That would explain losing voltage. Worse, it's a fire hazard. At a minimum I'd take the harness apart and rework that junction even if you find another cause for the headlights dimming. There's a 3G alternator upgrade that's worth doing on these trucks.

Finally, the headlights sockets themselves are of poor design, get very dirty, and fail....check those too, as well as the grounds to the body and the body to engine ground. These should be the first things you checks, but since your problem is with both lights its not as likely a solution unless its the body ground, but check the simple stuff first.

As far as the idle goes, sounds normal to me. Unless the high idle is over 2000 rpm, it doesn't sound like you have a problem. The only adjustment I'm aware of is to disconnect the IAC with the engine warm, and then adjust the idle stop so the truck runs about 600 rpms. Then reattach the IAC. Maybe the throttle body and IAC need a good cleaning. That's a fairly common problem.

 

Bill,
I fixed a bunch of wires for the headlights and altenator so I guess I should try the relay as my headlights still go dim on me. I found the screw you were talking about the for the idle and its stuck so i'm just going to grind it down until I get the idle where I want it. Thanks for the info.
Since it is a flare side I thought it would be neat to put smoke stacks on it, but can not find any systems online, and the ones I do find are for diesels and are way too big, I only need 1 3/4" or 1 7/8" pipes for the duel exhaust, not 6" or 7". Thanks again

Joshua

 

Before you grind your throtle adjustment screw, hit it with a good penetrating oil like PB and let it sit a while. It's exposed on both sides...there's really no reason it shouldn't come out unless its cross-threaded.

But before you mess with the adjustment, make sure the throttle body and IAC are clean. Also, you always want to pull codes on an EFI engine. Your problem could easily be something other than the adjustment.

Here's a site with details for the headlight relay upgrade.

Headlight Upgrade

 

You can't adjust the idle with the idle screw. The computer adjusts the idle, and you will just be fighting it, and causing more problems. Take the IAC motor and the throttle body off and clean them as the other poster suggested, and that will most likely cure your idle speed problem.