I replace the five exterior cab (roof) lights yesterday (on the 69 F350). But nothing happened when I turned on the parking or the headlights. I would have thought the roof lights came on with the headlights. I didn't get the headlight switch out before the rains started again, to check the wiring. I followed the feed wire from the roof lights down to a 3 plug connection behind the dash panel. Does that 3 wire connection go into the light switch? Or maybe the PO changed the power source for the roof lights?? Any ideas guys? One more thing to take out of the equation, I cleaned the sockets and replace both parking light bulbs- so those are working.

 

I'd remove the dash cluster so you can see an look where it comes out of the pillar & may be use a test jumper hot wire to make sure they light up from that point up.
Orich

 

There's a separate switch for the marker lights. I'll try to find it.
Here you go. I was looking for this piece and these are the numbers Jeff gave me.
C1TF15443A...marker lamp blinker switch...61/66 ALL trucks except E100,P/D,S/B before serial number s72,001.
C1TF15469A...marker lamp switch bezel.
(C1TF15A413A is the nut)

 

Does this apply to my '69 model too?

 

I'm sure it would work, however here's a thread with information you might need.
https://www.ford-trucks.com/forums/8...-troubles.html

 

That's the switch to blink the markers as in 'you are clear to merge.' Mine were just wired straight to the running lights, IIRC. I can check tomorrow when it's light again. I found a blink marker light switch so I can do the marker flash, but that is a F500+ item it seems. From the diagram, it comes off of wire 984, Brown, straight off the Light Switch. this does the front fender running lights. Might also be a breaker for the clearance lights.
Ford Truck Technical Drawings and Schematics - Section H - Wiring Diagrams

And there is. Check this one out:
http://www.fordification.com/tech/wi...350markers.jpg

 

I took the headlight switch out today. The cab lights are wired straight into the switch. I think my problem may be in the "Marker Lamp Relay" which was mounted on the pass side next to a circuit breaker. The breaker was burnt. I replaced it, but the relay doesn't do anything. The number on the relay case is: C8TB-13A435-A. I can't find the relay even listed in the catalog for :NPD, LMC, MAC, Dennis C., or restorations specialty. I looked at the NAPA, O'reilieys, and PEP boys too. So maybe Jeffefa, or Number Dummy can find a part number for it. I don't know if a horn relay is the same or not. I might give that a try next.

 

That wiring diagram shows the "Marker Lamp Relay" that I think is bad.

 

I found the relay shown in a couple of places so far:


this is for a '70 model




this break down shows it next to the circuit breaker

 

I have all of the platform markers disconnected and off now, so they can't be related to no power at the cab lights. I'm replacing them with LED marker lights next. NO RAIN FOR THE NEXT 3 DAYS!!!!!!!! I plan on being a fixing **** for this week!!

 

Led's are fine but they can cause all kinds of other problems with in your electrical system if you have not found out yet. I had to add a resistor to all parking lights & blinkers front & rears. Plus the blinker relay units.

Then when I thought every thing was "A"Okay a new problem popped up my cruise control unit is now not working an since it has a digital control box & not vacuum for a manual trans.

But then by adding the new digital main blinker unit it knocked out my cruise control unit. Which then requires a special plug in blinker filter for them to work slower.

So, I thought to hell with it for now an back tracked an put back in the regular blinker unit so, I can use the cruise control.

The blinkers do blink a little faster but screw it ask me if, I don't care at this point.
I don't watch it blinking any way just make sure it's working at first glance when, I'm turning.
Orich

 

Sorry Gary. Just caught your PM. I'm days and pages behind.
The Part number is C8TZ13A435A.

Nos Parts Source *Fo

913.220.5746


xGreen Sales

(800) 543-4959




xDennis Carpenter Ford

800-476-9653.

AND:


Premium Listings


Recently Updated<table class="static info_table"><tbody><tr><td class="label">Part Number:</td><td>C8TZ13A435A</td><td>
</td><td class="label">Seller:</td><td>NOS Parts Ltd. - View Profile</td></tr><tr class="even"><td class="label">Description:</td><td>RELAY ASSY.-TRAILER LIGHT</td><td>
</td><td class="label">Phone:</td><td id="phone_primary666801">(972) 937-2201
Tell them you found it on RearCounter.com</td></tr><tr><td class="label">Price:</td><td>Request Pricing</td><td>
</td><td class="label">Email:</td><td>Send Seller Email Inquiry</td></tr><tr class="even"><td class="label">Quantity:</td><td>3</td><td>
</td><td class="label">Location:</td><td>Waxahachie, Texas Map & Directions</td></tr><tr><td colspan="5" style="text-align:right; padding-top:5px; padding-bottom:5px">
</td></tr></tbody></table>


Recently Updated<table class="static info_table"><tbody><tr class="even"><td class="label">Part Number:</td><td>C8TZ-13A435-A</td><td>
</td><td class="label">Seller:</td><td>Miller Obsolete Parts - View Profile</td></tr><tr><td class="label">Description:</td><td>RELAY - AUTOLITE</td><td>
</td><td class="label">Phone:</td><td id="phone_primary174049">(607) 722-5371
Tell them you found it on RearCounter.com</td></tr><tr class="even"><td class="label">Price:</td><td>Request Pricing</td><td>
</td><td class="label">Email:</td><td>Send Seller Email Inquiry</td></tr><tr><td class="label">Quantity:</td><td>46</td><td>
</td><td class="label">Location:</td><td>Binghamton, New York Map & Directions</td></tr><tr class="even"></tr></tbody></table>


<table class="static info_table"><tbody><tr><td class="label">Part Number:</td><td>C8TZ-13A435-A</td><td>
</td><td class="label">Seller:</td><td>McDonald Obsolete Parts - View Profile</td></tr><tr class="even"><td class="label">Description:</td><td>
</td><td>
</td><td class="label">Phone:</td><td id="phone_primary106241">(812) 359-4965
Tell them you found it on RearCounter.com</td></tr><tr><td class="label">Price:</td><td>Request Pricing</td><td>
</td><td class="label">Email:</td><td>Send Seller Email Inquiry</td></tr><tr class="even"><td class="label">Quantity:</td><td>1</td><td>
</td><td class="label">Location:</td><td>rockport, Indiana Map & Directions</td></tr><tr><td colspan="5" style="text-align:right; padding-top:5px; padding-bottom:5px">
</td></tr></tbody></table><table class="static info_table"><tbody><tr class="even"><td class="label">Part Number:</td><td>C8TZ-13A435-A</td><td>
</td><td class="label">Seller:</td><td>Kama Obsolete Parts - View Profile</td></tr><tr><td class="label">Description:</td><td>Relay assy-</td><td>
</td><td class="label">Phone:</td><td id="phone_primary829301">(763) 434-0123
Tell them you found it on RearCounter.com</td></tr><tr class="even"><td class="label">Price:</td><td>Request Pricing</td><td>
</td><td class="label">Email:</td><td>Send Seller Email Inquiry</td></tr><tr><td class="label">Quantity:</td><td>1</td><td>
</td><td class="label">Location:</td><td>East Bethel, Minnesota Map & Directions</td></tr></tbody></table>

 

Thanks Jefffafa, the old guy (younger than me-LOL) at NAPA ordered me one (or at least what he thought was the correct one) I think that I'll order one from the list above just to make sure I have the correct one.

 

Since the lights worked before you replaced them, I would suspect ground. My replacement clearance lights on my 67 had two wires. I hooked the ground to the stud for mounting the light.

Also interesting to note that the 67 (at least the early ones) did not have a relay or a blink switch...

 

I need to figure this out before wiring my truck as well. I got my clearance lights off a f350 cab/chassis parts truck. It did not have a separate switch for clearance lights. I thought they just went on with the headlights. Next time I am around the truck I am going to check out the wiring. I left it all there and only took the lights. They have the single bullet plug on them.