Gentleman I have just finished installing some new Headlamps and a HD harness. This morning I attempted to hook up my new headlamp switch and found out that it didn't work correctly. I diagnosed the problem and traced it down step by step so here are my findings. It is a very easy fix provided someone shade-tree'd your truck in a similar fashion.

Before:


After:


What we are looking at here is a 1980 F150 headlamp switch and the proper 1981-86 headlamp switch assy.

The 80 is on the left and the 81 is on the right



I searched everywhere for the differences between the two to no avail, so I whipped out my trusty DMM and went all 'engineery' on it.

The switches as have been mentioned before are wired completely differently. I had no idea that this was a 1980 switch as I had a legitimate Canukistanian 1981 F150. It was an original 300 I6 swapped to a 302 sbf. There was the plausability that they switched the harness, but I found the wire that ended up being cut at the fuse panel.

Here are the discrepancies:

1980 Switch:

B hot to A at all times
B hot to R and I at first position (park lamps)

1981 switch



B is NOT hot to A anymore
B is ONLY hot to H at second position (headlights)
A is hot to I, R, and P at first position (park lamps and DRL if so equipped)
A is hot to I, R, and NOT P on position 2 (Headlamps)

Both Switches:
D1 only shorts to D2 when illum **** is set to cab light and does NOT use A or B for power

Now I know my harness has been destroyed. It was shade-tree'd together with speaker wire and wire nuts. They didn't even bother using zip ties either.... they used speaker wire also.

Here's a pic of my connector



Note the cut blue wire. That is supposed to receive constant hot from the battery.

Even though my truck is is from Canada, I do not have a harness provision for DRLs. It is likely this was removed.

I will be repairing this today so I can have my park lights function without having to jiggle my switch.

Thank you Gentleman for your help.

 

I've mentioned this here many times.

You cannot put a 1981-1986 headlamp switch into a 1980 or visa versa.

The horn power also goes through the headlamp switch on the 1980 by design.

Somebody moronically engineered it by your description. Possibly trying to add DRL's.

These trucks did not come with DRL's (Daylight Running Lights) as they were built before Canada mandated them. 1989 if I'm not mistaken?

Your HD Headlight harness came with relays right?

You could add a third relay that interupts power to it's main power line when its triggered.

The relay and the wiring you need would be designed something like this. 12v power with ignition switch on only in run, (heater blower feed is such a circut). Power would go through the 3rd relay when deactivated, to trigger your other two relays to turn on your lowbeams.

The main power wire from the headlamp switch that goes to your dimmer switch would trigger the 3rd relay to interupt power to the other relays when the headlamp switch was on. The headlamp switch will power the headlamp relays as normal.

The addition of a inline diode would complete the installation so power would not backfeed the low beam circut when in DRL mode.

The addition of this third relay would be to prevent forced lowbeams with the headlamps on high beam.


Something along these lines in this makeshift schematic...


There are also DRL universal kits that you can buy. Other than those suggestions, just make sure to turn the headlights on everytime you drive and do not forget to do so.

 

Actually I found its quite simple to put a 1980 in a 81-86. You cut the blue hot from battery and it works.... albeit dangerously. I repaired the blue wire that goes to A and it now works normally. I can add DRL if I so choose now because I now have a spot to plug into. Just need a drl kit.

Also my HD harness is working great. The way they derped this up is clever but dangerous, as they were putting a huge load on the Headlamp switch. Not to mention all of the retardo-rigged lighting and stereo equipment. The lights now work perfectly. Now I just have to figure out what happened to my reverse lamps...

 

Why not fix it properly?

Get the proper headlamp switch and fix the wiring, it's really not that hard to do.

Mix and matching the switches will at best cause functioning faults, at worst you will cause a fire.

The circut breaker loads between the two switches are different. 1980 switches are not rated to handle halogen headlamps 10 amp CB, the 1981-1986s are rated 18 amp CB. The 1980 switch has circut breakers to protect the parking lamps and horn. The 1981-1986 uses fuses in the fuse panel for this function. Using the 1980 switch you are backfeeding the Tan/white stripe wire back to the fuse panel.

You yourself even admit it's dangerous. I wouldn't risk my truck for a $15-30 switch.

By the way the only blue wire on the switch is the Light Blue/Red wire for the instrument cluster illumination. So either it's a color they added, or you just disconnected your instrument cluster lights.


1981-1986: Wire Colors at headlamp switch

1: Black/Orange stripe: Power from Battery Feeds Red/Yellow stripe wire.
2: Red/Yellow: Headlamp main feed to dimmer switch

3: Tan/White: Parking Lamp and Instument illumination power feed from fuse panel: Feed for Light Blue/Red and Brown wires
4: Light Blue/Red Stripe: Instrument cluster illumination
5: Brown: Parking Lamps

6: Light Green/Yellow: Courtesy lamp feed, powers Black/Pink Stripe wire
7: Black/Pink stripe: Dome Lamp and Cargo Lamp feed from switch

1980: wire colors at Headlamp switch:

1: Black/Orange stripe: Power from Battery: Feeds Red/Yellow stripe; Yellow Blue Dot; Brown and Light Blue/Red stripe wires.
2: Red/Yellow: Headlamp main feed to dimmer switch
3: Yellow Blue Dot: Horn switch and cruise control main feed
4: Light Blue/Red Stripe: Instrument cluster illumination
5: Brown: Parking Lamps


6: Light Green/Yellow: Courtesy lamp feed, powers Black/Pink Stripe wire
7: Black/Pink stripe: Dome Lamp and Cargo Lamp feed from switch

 

I did fix it properly. That is what I am saying. Haha

 

Not if you are using a 1980 headlamp switch in a 1981-1986 I will have to respectfully disagree.

Here are the factory wiring diagrams to help you, and I included the 1980 Power distribution diagram so you can compare the different circuts. Notice the 1980 is wired completely different to the 1981 and later.



1981-1983 Power Distribution diagram


1980 only Power Distribution Diagram for comparison



1981-1983 Exterior lighting Diagram for your backup light problem.

 

I think you misunderstood my first post. The previous owner hacked up my harness in order to use a 1980 switch. All I had to do was repair the 'A' wire and it fixed my issue. I'm not one to half-*** something. I am in the process of undoing the stupid crap they did to this poor truck. The object of the initial post was to post my findings on the difference between the two switches. Thanks for the reverse diagram. I'll be taking a look at it later tonight.

 

Sorry, yes I did misunderstand you then. I was worried that you were heading toward burning the truck down. The Tan/White wire of 1981-1986 is prone to overheat with it hooked up correctly. With the 1980 switch backfeeding that wire using a mis rated circut breaker with no fuse protection on that side of the wiring, might have been problematic.

Those diagrams should help you sort it out, and with the 1980 diagram as a comparison, you shoud be able to find out what they did and fix it.