Tuesday, September 11, 2012

Hidden Gremlins

One of GM's engineering marvels in the 60's were hidden headlights, or more specifically, hide away headlights. Starting in 1963, Chevrolet used them on their newly restyled Corvette and they more or less became a styling fixture on the car. Then, in 1966, GM designers decided to grace the front end of the Olds Toronado and Buick Riviera with hide away lights also. Next up to use these unique lights was the 1967 Camaro, which is the subject of our story here. The main difference between the '67 and '68 systems is that the '67 systems were equipped with electric headlight door motors, versus vacuum operated for '68 on up. A lot of work went into engineering these early systems, as anyone who has ever worked on them can attest. I can now put myself into that latter catagory, as I recently had the pleasure (?) of diagnosing and repairing a hidden headlight system on a '67 Camaro.
They look great all closed up which is the way these wanted to stay - permanently.

The first thing I had to do was track down a wiring diagram for the Camaro's headlight system. This is easier said then done. Wiring diagrams or schematics are essential in helping to diagnose problems and locate components. After some heavy duty searching I managed to locate a really nice schematic drawing of the 67's unique hide away headlight system. Pouring over the diagram I discovered that it contained no less then four relays and two breaker type fuses. These "fuses" are unique because instead of blowing out like a conventional fuse, they act more like a circuit breaker in a house electrical panel. When the load across them becomes too great it heats up a bi-metal spring contact which separates and breaks the connection. After some initial testing for voltage at the headlight motors, I decided I would start with these fuses, as it seemed to be a power problem (or lack of) that was keeping the Camaro's headlights from working.

As it turned out, one of the fuses was bad. These puppies were rated at 30 amps so they can usually handle a load pretty well. I took it apart and it looked like it got really hot on the inside, almost like it was shorted out. Because these are a stud type breaker you can't exactly find replacements at the local parts store, so I had to get creative. I used a heavy duty, weather tight, 30 amp spade type fuse holder and crimped an eyelet on each end to go over the studs on the breaker. The breaker might not be any good anymore but it would serve as a mount for the inline holder. I ruled out a short in the system so what could have drawn over 30 amps to cook the original breaker? The only component capable of doing that was the headlight motor, but the owner told me they were both brand new. Now what?

More testing was needed to determine what caused the breaker to fail. Plus, after installing the new fuse, only one headlight motor started working. Well, at least it was half way fixed! After I applied 12 volts directly to the non-working motor it still wouldn't work, so I had no choice but to remove it. The only problem is that in order to get to the electric motor you have to take out the entire headlight bucket assembly. Now I know why shops charge so much for electrical work! I also realized that I don't charge enough...

Once the motor was out and on my work bench, I took it apart to see if maybe one of the brushes broke or something. Everything looked good inside the motor but I knew it didn't work so something had to be wrong. I decided to test the armature and that's where I found the problem. The motor was either shorted out or got stuck while under power and it burned up the thin wires going from the commutator to the armature windings. With the breaker taking the brunt of this it's no wonder it failed. A new motor was ordered and on it's way, but would that solve all of this Camaro's headlight problems? In a word, no!

Once the new motor was hooked up I quickly discovered what burned up the other motor. You see, on the 67's headlight system there are limit switches, two per side. Their purpose is to kill the voltage to the motor (via the relay and aforementioned fuse) when the headlight door is in either the open or closed position. On this particular side the limit switch for the closed position was out of adjustment causing the motor to run continuously. The original motor probably overheated and the resulting amp draw damaged the breaker and fried the motor's armature. After the limit switch was properly adjusted, the Camaro's headlight system worked perfectly - well, almost. In my experience, electrical systems usually have more then one problem and this one was no exception.

 The last item the car suffered from was a dim headlight, one that I was told had plagued the Camaro for awhile. Changing out the headlight did not work, so I had to go back to the drawing board, literally. After pouring over the schematic and double checking all the connections, I discovered a ground lug that had been cut from the headlight harness. Apparently someone was in a hurry when they removed it at one time or another and never bothered to hook it back up. A word to the wise - grounds exist for a reason! Hook them up and don't feed the Gremlins!

1 comment:

  1. What an awesome Camaro, great job on the restoration work. I just did some restoration work on one not to klong ago.