[DeTomaso] electrical help

[MikeLDrew at aol.com]

In a message dated 8/11/09 18 22 13, justingreisberg at hotmail.com writes:


> 
> big headlight problem - the headlight swtch properly works the parking and 
> head lights themselves, but the headlight motor puts them down when on, 
> and raises them when off (opposite what is supposed to happen).   I am pretty 
> sure the problem is in the headlight relay, which was all messed up when I 
> got the car.  Itried to rewire based on the wiring diagram schematic, but 
> it seems I crossed a wire.  Any suggestions to fix this easily?
> 

Full disclosure--I know *squat* about electricity.

That said, when all else fails, "RTFM" as they say, which stands for "Read 
The Freaking Manual" :>)

Or in this case, Ford's Technical Service Bulletin #14.

Partway through the 1974 model year, a new headlight relay was introduced.  
 The early one was D16Y-14516-F, and the later one was D46Y-14516F.   
Externally they are identical, and they are NOT marked.   With the relay 
installed in the car, the only way to tell what kind you have is to check the wiring 
running to it.   With the relay out of the car, the only difference is a 
small bridge wire that connects the two ground lugs.

It just so happens that in my fairly massive NOS parts stash (which I'm 
still inventorying, if that's a word), I have both the early and late style 
relays, new in the box.   Check out the photo below, and click on the link to 
view it full-size:

http://www.poca.com/index.php/gallery/?g2_itemId=9956

Look where the yellow wires connect to the second-from-the-left tabs.   The 
late relay on the right has a bridge wire connecting it to the adjacent 
tab.   Although you can't see it in the photo, the bridge wire wraps all the 
way around and thus it connects on both the front and back sides of the tab.

Chances are, your car has a later-style relay, and both the factory wiring 
diagram and the Bill Taylor diagram won't accurately reflect the proper 
connections.   The TSB #14 has a wiring schematic for the headlight relay that 
is totally different from the 1971-early 1974 cars.   If you follow that, you 
should have no problems.

You do have the TSBs, right?   Does anybody *not* have the factory shop 
manual plus the TSBs?

#14 has all sorts of information about the headlight system.    Along with 
the change to the later style relay, a circuit breaker was introduced into 
the up-down power circuit, I presume to prevent the motor from burning up if 
one of the limit switches failed.   Another article in the TSB talks about 
headlight motor replacement, and although it doesn't specifically mention the 
reasoning behind it, the motor-changing procedure also includes a very 
involved procedure that calls for hacking and splicing the wiring on the early 
relay setup to add in an external circuit breaker to retrofit this feature to 
the earlier cars (and yes, I have the appropriate circuit breaker in my 
parts stash too). :>)

Bob Leavitt was curious as to why the 1974 factory replacement headlight 
motor I sent him recently   didn't fit into the mounts.   The TSB addresses 
that situation, and explains that the new 1974 motor has different physical 
characteristics from the 1971-73 motors, and goes on to explain exactly how to 
modify the mount to accept the new motor design.   (And yes, I have an NOS 
1974 motor in my parts stash as well, and the studs are about 1/4 inch 
closer together than the 1971-73 motors).

Good luck, and let us know if this gets you sorted out! :>)

Mike