Hey everybody

1978 F250 4WD SC CS

Attached is a pic of my headlight switch.

Yet another quick question. I can't make out the numbers on my switch because of corrosion, but in doing research I'm finding that it might be D2AB 11654 AA. (can't make it all out, but I'm sure of D2AB, the 65 and the AA). I look that up, but come up with an 8 terminal switch. Ford's part site didn't have a result for that number, but did have one by application. It has 8 terminals.

Looking at the pick, I only count 7 terminals. The "P" lug is not there, and looks like it never was. I did find this in another thread:

Light Switch

B ------------ Battery positive
A ------------ Battery positive to other
R ------------ Park / Tail lights
I ------------ Dash lights
H ------------ Headlights to dim & bright switch
D1 D2 ------------ Interior light

I count 7 there, as well.

So "P" is not needed on my truck? I would prefer a Ford part as opposed to questionable overseas stuff. I assume that Ford is correct (?) and their part by application will work, just have the P lug connected to nothing?

Maybe it wasn't so quick a question as I thought!

 

The replacement switch is Ford p/n D3AZ-11654-A, Motorcraft p/n SW1226.
Everything I find on this switch shows it as an eight terminal switch, same for the pictures, they all show eight terminals.
On the wiring schematic for the '78 it shows seven terminals.
Look at the socket on the wiring harness. Is there a space for the eighth terminal to fit? If there is, it should be blank (no wire, just a space). If it's like that, I would order the switch and try it. This could be a replacement number that is designed to fit multiple applications.
If there is no space for the eighth terminal, that's a different story.

 

Thanks, Mike

As soon as I'm off grandbaby duty I'll check it out. It might not be the problem, but I'm researching everything. Might just be that I used too much dielectric grease and over coated the terminals where I plugged in the H4 relay harness, but I'm up to elbows in diapers and bottles right now! Wouldn't trade it for the world, though. She's 6 months and a very good baby!

Plan is to clean connectors of grease, then plug in one of the old headlights to test the switch/system. If that doesn't work, I'll check my grounds. If it does, I'll suspect the relays.