66 fullsize headlight problem

[pdecheine]

I have a 66 Catalina. The wire that runs from the headlight switch to the dimmer switch overheated at the connectors on both ends to the point it melted the plastic pigtails. I replaced the dimmer switch, no fix. I replaced the headlight switch and now the breaker will trip if i use the high beams with engine running. The circuit draws 11 amps with high beams on. I cleaned all contact points on both switches and replaced the burned wire and connectors. None of the other wires show signs of overheating Help!

[Larry]

I'm guessing that the burned wire ends were caused by a high amp draw of some sort. I have no way of knowing, but 11 amps sure sounds high.

Check our On-Line Service Manual 1966 book and look at the wiring diagram. I wil check it also in a bit.

Is there a realy or resistance wire any where in the circuit.

What has engine running vs. not running got to do with this? That is odd. I'll get my thinking cap on.

[pdecheine]

Thank you for your response. I have discovered that the circuit breaker integral with the headlight switch is rated at 15 amps. If I test the lights at home, I have run them for 10 minutes with no problem. If I am driving at night and have had the headlights on (low beams) for 20 minutes or so, the breaker trips within 30 seconds if I engage the high beams. I wonder if the new headlight switch might have a faulty breaker.

[Larry]

What happens if you engage the high beams while the car is sitting still at home? Does it trip then? Or is it only when you are moving.

If it only trips while moving, it wouldn't be a faulty breaker (I wouldn't think). It would trip when you activate the high beams whether moving or not.

If it only happens when you engage the high beams while moving it would be a very strange situation, but it would certainly point away from just the switch breaker.

Does the breaker in the switch reset itself after tripping? I guess 11-15 amp isn't too much when you consider the low voltage.

[pdecheine]

The breaker is definitely tripping, the flickering is due to the fact the breaker is a bi-metallic spring that will bend at a certain temperature and then spring back when it cools. This is to prevent sudden, total loss of headlights if the circuit is overloaded. My problem seems to be the breaker heats up gradually as the headlights are in use and then trips when additional load is added if the high beams are engaged. I haven't been able to duplicate the problem in the driveway so your suggestion about vibration causing an intermittent short will be my next detective mission. Interestingly enough I had the exact same problem with a 67 Ford Galaxie about 40 years ago.

[Larry]

I had a '66 Fairlane GT while in the Air Force that started having headlight blackouts- suddenly. I replaced the switch assembly... same thing.

One night while driving back to base after working at a service station in the evening, they blacked out again. Despirately I reached up under the dash (at about 70mph in the pitch dark!) for no reason other than not knowing what else to do. Guess what, a tinnerman nut from somewhere up in the dash had fallen out and was bouncing around under the dash, periodically popping onto the exposed switch contacts.

Other than a nut with some burned edges, and never finding out where it was supposed to go, all worked 100% from then on. That's why I was wondering if moving could be part of the problem.

Can you pull out the switch and let it hang under the dash while you drive around trying to duplicate the problem. Periodically wiggling and pulling on it might produce some interesting results.

As a real long shot, does your '66 have a big electrical plug on the engine side of the firewall near the steering column/above? My '67 Ventura had freaky electrical troubles (including total death) until I pulled that off and used solvent to clean out all the factory yuck they put in to stop corrosion.

[pdecheine]

Thank-you for more suggestions. I have ordered a replacement for the headlight switch. The problem surfaced after I bought a new one last month so hopefully that solves the problem. I will, however, continue to clean connectors and check wiring...

[Larry]

When all else fails, resort to the last thing you changed. Actually with the crummy quality of today's products, it is probably the most likely cause.

Heck, we recently had to got through three bicycles from Wal Mart and K-Mart for our 2-year old grandson before we got one that didn't have the bottom of the seat all split and torn or the front fork tube welded on so crooked he would have only been able to ride in circles.

Perhaps the breaker in the new switch was weak and when the "shock" of the extra load was put on (hi beams), it would trip.

You know what might have been interesting to try, is to put your hi beams on with the light switch off, and then see if all stayed on when you pulled out the knob.

I think a new switch is in order though. Enough experimenting.

[pdecheine]

I installed the new headlight switch and it seems to have solved the problem. YAY!

[Larry]

I don't know what it is about electrical problems, but I have found that I have to force myself to think in the simplest terms.

It is usually, however, related to, or actually, the last thing we did. When it comes to installing new components, we have the usual tendency to trust that they are good.

I have WAY too many stories (read: experiences) when it turns out the probblem was the "new" component, or the first, easiest thing that I thought of.

Glad you got it solved. Have you sent the old swith back with a "special" note?

[pdecheine]

Unfortunately my headlight problem resurfaced last weekend. This time the problem of the mysteriously tripping breaker occurred with the low beams. I rechecked for shorts with a test light instead of a continuity tester and found none. I bought 2 relays and a circuit breaker, and wired so the headlights get power directly from the battery. problem solved (fingers crossed). Interestingly enough, another problem was also solved. ever since I bought the car 16 years ago the ammeter would "flutter" and the headlights would brighten and dim in time with the flutter. I had replaced the voltage regulator and the engine compartment wire harness as well as cleaning all grounds and buying new ground straps from engine to frame. The addition of the relays solved that problem.

[Larry]

I wonder if the voltage regulator might have been a problem that only acted up with the draw of the lights (which is pretty high), and then made the lights trip.

Regardless, you solved with the new wiring and hopefully will not have any further problems. I did the same thing with new relays on my '40 Pontiac years ago just to get brighter lights. A more direct shot from the battery helped.

What happens to the ammeter when the hearer blower is on full speed?. That draws a lot too. Might it flutter too?