Power Window Power

March 19, 2007 7:48 PM

Can anyone with classic car restoration experience help me with a strange electrical problem that I'm having with a 1961 Lincoln Continental?

This car came with a feature where by the rear power windows would descend about an inch or two upon initial opening in order that they clear the deployed soft top. When shut, the window would then re-extend itself into the fully closed position. There's a pin switch in the door frame that, when the open door allows the spring tension to close the switch, a relay in the trunk is energized and the window motor is activated. There's a limiting mechanism in the door that cuts power to the motor after the window has descended the correct amount. When the door is shut, it actuates the pin switch again, and the motor scrolls the window up until the limiting mechanism de-energizes the motor to prevent it from running constantly.

At least that's what I can gather.

Only, this neat feature doesn't work with any consistancy. I know that the circuit is correctly wired and intact because it works SOMETIMES. I can hear the fist-sized antique relays clunking away in the trunk and I can consistanty operate the windows using the conventional switches. I can even sometimes roll the window down a little bit with the conventional switch and then actuate the pin switch in the door frame and watch the window roll up, like it's supposed to.

So there must be some problem with the limiting mechanism, right? Can anyone in MeFiLand lend me some insight or point me towards a (free or really inexpensive) resource that would shed some light on this for me?

posted by Jon-o to technology (7 comments total)

Does the feature work with just one door, or both doors?

You've got three areas to look at -- the limiter in the door, the relay in the trunk, and the wiring in between. Any one of the three may have gone bad. The wiring can go bad from rubbing on the inside of the frame so that there's a bare spot that *SOMETIMES* grounds out, which puts the current into the frame of the car instead of tripping the relay. The switch can get dirty (likely, inside a door) or the relay can just go kaput. The most likely is the wire from my experience with classic cars and motorcycles.

(We used to own and MG-B. With electrics by Lucas, the Prince of Darkness...)
posted by SpecialK at 8:00 PM on March 19, 2007

Heh, this is beyond me but I thought I'd peek in here because as a former MG-B owner, cars with electrical problems perk my ears. So, I just had to comment when I saw what SpecialK wrote.
posted by amanda at 8:15 PM on March 19, 2007

I would also recommend checking the wires for corrosion. Corrosion can increase resistance significantly, and (depending on atmospherics), lead to a situation where most of the time there's too much resistance to operate, but once in a blue moon the current finds a viable path and lo and behold, things work. When rebuilding these old components, like the OEM relays, something like dielectric grease is your friend.
posted by mosk at 8:15 PM on March 19, 2007

"...Lucas, the Prince of Darkness..."

The old jokes are the best, SpecialK. I used to have an MGA Twin Cam and Triumph TR4, and kept #2 Phillips screwdrivers handy in the cockpits, to steal back my tail light lenses whenever I found them parked on another car. I always wished Lucas would have made more than the one pair of those, so that others would have left mine alone :-)

But, as to the OP's question:

As the problem is intermittent, the cause is most likely wiring. The car is now 46 years old. The insulation used on wiring looms of that vintage wasn't all that great to begin with, and I saw cracked wiring insulation in a 1960 Lincoln I had as early as 1969. Second most likely cause is the relay. You can probably remove and open the relay, and use a contact burnishing tool to clean and polish the relay contacts. Never use sandpaper or abrasive on relay contacts; a burnishing tool doesn't really remove contact material, and is far less expensive or hard to find than replacement relays. It would also be a good idea to clean the relay pins and the socket, using the burnishing tool, or clean cardboard strips, such as paper matches, too.
posted by paulsc at 8:21 PM on March 19, 2007

If paulsc's regime doesn't clear up the problem, look to the switches. FoMoCo has a long history of bad switches.
posted by Kirth Gerson at 4:32 AM on March 20, 2007

As a classic car owner myself, I frequently utilize the power of the internet to solve problems like this. If you aren't already I would suggest finding a few online forums and see if anyone there can help. It looks like there are several active ones.
posted by Big_B at 8:13 AM on March 20, 2007

While checking your wiring circuit, you should also examine the ground path to your battery as circuits are often grounded to the nearest body panel which can be held in place by only a few spot welds.
posted by BigBwana at 11:00 AM on March 21, 2007