Help! Low beam switch on a '88 F150

[Muley Gil]

I was driving my '88 Ford F150 yesterday, in the misty rain,and when I pulled up in a friend's carport, I didn't see a reflection of my headlights. I hit the high/low switch and I had high beams, but no low beams, on either side. My '95 Isuzu had both low beams go out at the same time a number of years ago & I figured the same thing happened to this old Ford. BTW, the switch is on the floorboard.

I bought new lights today and started swapping them out. I installed the right side and turned on the headlights. I had high & low beams, on both sides. :roll: I swapped out the left side and now I have high beams only, no low beams. I'm guessing I may need to replace or repair the switch.

Thoughts anyone??????

 

[daveg.inkc]

Maybe a ground wire? Have you looked at connection on dimmer switch?

 

[Muley Gil]

Not yet. I'll do that this weekend.

 

[Jeepnik]

Had the same thing happen on my '78 Ford. I just replaced the foot switch and every thing was fine. Robust things but after 30 some odd years it went. Replacement was inexpensive and took longer to find the tools than to do the job.

 

[Muley Gil]

Back in the 1980s, I had to repair the switch that was in my '52 Buick Super. Like you say, they only last about 30 years or so. :D

 

[wheelgun1958]

Try the floor switch (cheap and easy). If no help you may have a wire issue between splice s811 and left lamp.

 

[powder smoke]

Got a bad switch? Replace it! ps

 

[sceva]

On another note; I loved the floor switches and miss them. I did not like the change to the turn signal / brights switch and even after many year I still wish they would go back to floor switches.

 

[gjgalligan]

Any chance the low beam bulbs are bad?

I learned the KISS method years ago.

Keep
It
Simple
Stupid

 

[Muley Gil]

Any chance the low beam bulbs are bad?

I learned the KISS method years ago.

Keep
It
Simple
Stupid

That was my first assumption, as I had both low beams go out at the same time on an Isuzu truck years ago.

See my initial post.

 

[Dan in MI]

Check your grounds on both sides. The switch is not bad. The circuit is back feeding due to bad ground.

If wheel gun has the whole book it will tell you where G801 and 802 are. I suspect they are on the core (radiator) support.

The switch controls both at once. It cannot differentiate sides. Look at the diagram it only has one wire going out for each level of brightness.

 

[Dan in MI]

Any news?

The more I look and read your symptoms, the more I am looking hard at ground G801. Follow circuit 12 or 13 from the switch. They will create the same issue. Power comes out from 13 it goes to the lo beam headlamp. Normally at this time it will light up the lo beam (both sides) and head out circuit 57 to ground. If the ground is bad on the left side the power will search for a ground. So it goes through the lo beam and the high beam bulbs and back feeds the system (circuit 12) to the right side and out the circuit 57 to ground 802. 12 would just feed into the lo on the right side to get to ground,.

 

[Muley Gil]

Saturday, I replaced the switch. No change. I found the ground wires on both sides, screwed to the inner fenders. I loosened and retightened both. Still have no low beams. :(

 

[Pat-inCO]

Saturday, I replaced the switch. No change. I found the ground wires on both
sides, screwed to the inner fenders. I loosened and retightened both. Still have no
low beams. :(

While you were in there, did you by chance use either no-ox or G.B. OX-Guard?
Just tightening the ground connections may help a little, but will not fix it.

When you changed one bulb and suddenly had high and low beams, that strongly
implies a lack of continuity in the ground connections. Either no-ox or Ox-Guard
will supply the connection you need.

P.S. The Ox-Guard costs about $4 for enough to do hundreds of connections. :wink:

 

[Dan in MI]

The back feed may have cooked the filaments. Remove both bulbs and reinstall each one separately. IE; do not hook up both before checking each side individually. As you noted earlier the right side worked by itself. See if the left does the same. Maybe the ground wire at the connector or between connector and screw is bad. (still thinking left side) (also Left and right is determined as if you were in the seat)

If you have an OHM meter check continuity between the ground and the battery or better yet each plug ground wire to the battery.

 

[Muley Gil]

Been real busy working on other projects. I don't drive this truck often, so it hasn't been a high priority. An old buddy of mine came to visit and he got on it with my volt-ohm meter. This truck has a snow plow and Bill traced the problem down and felt that the light relay may be the bugaboo. Found one at Cole Chevy in Bluefield WV, thanks to Shane the parts guy, since this plow has been discontinued I replaced the relay and I now have high beams AND low beams. Thanks to everyone on the forum for their help.

 

[Dan in MI]

Glad you fixed it, but the plow part was a huge detail to leave out.

 

[wiz1997]

Did you know when they moved the switch from the floor to the steering column there was an increase in accidents involving blondes?

They kept getting their foot caught in the steering wheel.

 

[wiz1997]

Double tap.

 

[Poco Oso]

Glad you found your problem. At least you caught it in the daytime. I had mine quit, while heading home, on a winding two lane at night. Brights were on, stepped on the switch (yep, on the floor, '79 F-150) to dim them, and everything went dark. A bit of excitement for sure, although probably not as much for me, as for the driver of the rig coming towards me when I dissappeared.

 

[Acorn]

Glad you found your problem. At least you caught it early. I had mine quit on a winding two lane road at night. Brights were on, stepped on the switch ('79 F-150) to dim them, and everything went dark. A bit of excitement for sure. Although probably not as much for me, as for the driver of the truck coming towards me when I dissappeared.

I was at the wheel of a rented class a motor home steeming up Route 79 about 75 mph about 10 PM on night and caught a whiff of something burning. Just a whiff. I asked if anyone else smelled anything and no one else did. A couple minutes later I smelled it again only stronger. Then the lights went out. YAHOO!!! I could see nothing. Hit the brakes and tried to hold it straight. Turns out the rental companies “mechanic” had “repaired” the wiring with smaller ga. wire than the rest of the circuit and used those blue Scotchlok connectors. The repair couldn’t handle the load and fried. It was a thrill to say the least.