2785 << Message Index >> 2787
Number: 2786
From: "InfoSysSec" <infosyssec@i...>
Date: Wed May 28, 2003 1:45 pm
Subject: Re: [ASC McLaren ] electrical problem

Body:

This topic was previously discussed and nicely explained. The short ( no pun intended ) answer is that the Ford switch is not strong enough to handle the amperage drawn when powering fog lights and head lights. There was a link provided in a previous message that takes you to a web page where there are schematics on how to wire in an extra relay in to the circuit so that the fog lights draw their own power supply and the amperage is not routed through the headlight switch. It is known as the 'fix that Ford SHOULD HAVE done on a recall but chose not too...

As for that horn problem... it could be one of three things... a short in the horn at the steering wheel - a problem in the relay for the horn or a short occurring right at the horn itself. I just went through the same problem myself when fixing my McLaren. For example, in the horn piece at the steering wheel, on the 1988 model Mustang/McLaren, you basically have under the leather cover two copper plates separated by some springy foam. Over the years the springy foam in the horn goes dry, brittle and falls apart. Basically no longer springy and not able to keep the two metal contact plates from contacting each other. The fix in that case is to pick up another horn piece or to take apart the horn thingy scrape out all the degraded foam and replace it with new spring foam ( I used foam rubber pads that were designed to be used under furniture to keep chairs from scratching the hardwood ). That horn piece now has lots of spring to it in order to keep the contacts separated except when I am hitting at the horn.

Within the horns themselves, there is the potential for a fuse to blow if the horn itself has problems. Easiest way to eliminate the horns themselves as the cause is to buy a cheap $16 regular horn and snap connect it into the circuit and see what happens. If things work great than you have successfully identified the original horns as having reached the end of their planned life cycle.

Lastly is the relay unit itself. Normally these things either work or die. They don't tend to go into a dead short circuit. But if your horn mechanism and the horns are both operating properly and still your system is shorting out than the relay would be the last suspect.

Well... there is one other suspect and it is so obvious that I didn't mention it originally... that being that the fuse may no be the right amperage.

I have heard though that there is one other potential problem area... and that ties in with the headlight problems you are mentioning. On occassion the over amperage of the headlight/foglight situation causes them to physically MELT their wiring. It is possible that a melt down in that wiring could lead to a potential short situation to be created that would be noticable when the horn is hit. In that case you have to thoroughly investigate ( follow ) the wiring for the horn circuit and the headlight circuit to make sure that the wiring hasn't been physically damaged by the heat.

Marq

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76 Mercury Capri GHIA / 77 Mercury Capri RSX
http://www.mercurycapri.com
Still working on it!

----- Original Message -----
From: mauro amato <mauro@djmauro.com>
Date: Wednesday, May 28, 2003 12:31 pm
Subject: [ASC McLaren ] electrical problem

> has anyone experienced this?? 2 issues
> 1.I turn on my fog lights and for about 15 min their fine...after
> that, they make my head lights blink on & off .its like the car is
> possessed or something. I turn them off and my headlights are normal
> again.
> 2.another issue is when i hit the horn on the car .....it works for
> about 2 sec. and the blows a fuse.wierd huh.
> I ran into another Mclaren owner and he had the same exact problem.
>
> iam gonna be putting in a coil over kit this weekend and since Iam
> gonna be under their I might as well fix these issues.
>
>

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