Sereral months ago I picked up a 1981 Corvette that apparently had a lot of electrical issues (ie stuff not working) that appear to be assocaited with electrical corrosion or borken switches. I replaced the headlight switch, wiper switch and even pulled the dash and then the fuse panel to check and clean all the contacts. Two nights ago was the first I had it out at night and driving down the toad at 55MPH THE HEADLIGHTS WENT OUT - switching between high beam and low beam had no effect (ie neither worked) . All other lights are working fine. I was only 2 miles from home and had a friend come and he got in front of me so i continued home following him for lighting. During that short trip the lights on and off briefly a few times but mostly off. OVer the past few days I have tried shaking every connection I could find. disconnecting and reconnecting the headlight switch. I sprayed a few location with electrical deoxidizer. Last night I took it for a short ride and seemed to work great until I pulled into driveway and they went off. I need help and advice as to what could be wrong. WHere is the headlight fuse? I don't see anything on the fuse panel stating headlight. This SEEMS to be something that happens after the lights have been on say 10-15 Mins. Almost like there is an automatic resettable Circuit Breaker.

 

Its very common for the headlight switch 7-terminal plugin to get burned terminals that don't make a good connection. My '82's OEM headlight switch failed at less than 50,000 because of a burned plugin that also burned the terminals of the switch up.

 

That's exactly what it is. Such have been used for headlights and wipers for decades. The circuit breaker is built in to the headlight switch.

Chevrolet wasn't particularly generous with wire sizing on the Corvette. Generally there is no problem with the stock headlights, but high-powered aftermarket lamps can cause the breaker to repeatedly trip. Also poor connections can cause a problem. Have you cleaned the connectors at the headlights?

A very common work around for the undersized wiring issue is to use the stock wiring to only operate relays which get their power from the alternator output via a 12 gauge wire. If you do such be certain to protect the new power supply with an appropriately sized self-resetting circuit breaker (best) or fuse (better than nothing).

 

If it is a wire, there is a known weak spot. It's on the drivers side infront of the radiator. The harness turns towards the passenger side. Right at that bend, wires are known to break.

 

Mike's correct on the circuit breaker in the headlight switch.

Two things to check-if you still have stock headlights...

One is the ground- I believe there is one on the left and one on the right side for an 81. IF you have a bad ground- the headlights will pull more current and cause the breaker to trip. Clean up the contacts- terminals and see if that works.

Second- is the "new" switch- probably made in China and the quality might be suspect. If you have cleaned up the grounds/terminals and lights look bright- if the switches breaker keeps tripping- it might just be the problem.

Unfortunately these days replacing with new part way to often IS the problem!!!


Here's a diagram for your car-
http://www.keystonestatecorvetteclub...tte%201981.pdf

 

Does the breaker only trip with prolonged use of the high beams?

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A bit about your headlights:

Your original high beam (inner) bulbs are trade #H5001 which are single filament 50W halogen bulbs.

Your original low beam (outer) bulbs are trade #4000 which are dual filament 37.5W + 22.5W (60W total). I can't confirm that totally as at some point after 1979 (82?) I believe that trade #H5006 (35W + 35W) was substituted. The "H" in the number stands for "halogen".

ALL THREE filaments burn with the headlights on high beam. Given the wire gauges in the system any substitution that uses higher wattage is likely to cause problems.

Extremely narrow beam and quite high wattage (75W-100W) lamps originally used as aircraft landing lights are fairly common aftermarket substitutes for the high lamps and nearly guaranteed to trip the breaker.

Even H5006 replacements for the now nearly impossible to find 4000 low beam bulbs draw 15 more watts per side and combined with some poor/dirty connections may well cause the breaker to trip.

And as mentioned the quality of replacement parts (especially from China) is dismal and you cannot assume that they will either work upon receipt or perform anywhere near the original specifications.

 

THanks much for the diagrams - I have the big diagram wiht everything on it but this one here is much easier. You mention the two grounds - I see them up front and pulled the RH side - cleaned it, and the 2 wires going to it. One was the horn wire - THe other, not sure but i ohmed it out and it was zero (ie straight to grd so I don't thing that went back to the light)

 

Cleaned the grounds up front and the contacts on headlights and plugs to them. Turned on headlights. Ran 30 mins - no problem. Turned on high beams - died in 3 mins- automatically turned back on for just a second twice. Now headlights don't work at all. I am gonna disconnect switch and hot wire (with an inline fuse) the switch power and yellow wire and see if it blows fuse. Any idea what amperage the CB is in the switch? If it pops, my problem is external to the switch (but I probably fried current one) if it doesn't pop problem is the switch. You guys agree?

 

Have you determined which lamps are installed?

If similar to the originals the circuit should draw about 18-21 amps with the high beams on. Sorry, but I have no idea of the size of the circuit breaker in the headlamp switch. All the literature I find just says something like, "Built into headlight switch" without giving a value. If I had to guess I'd say either 25 or 30 amps.

Besides the connections at the starter solenoid, the fusible link that immediately follows such and the fuse box connector through the firewall there is another connector in the main power before it gets to the headlamp switch. It is a heavy duty 6-conductor (5 used in my '79) connector very close to the hood alarm switch. One of the 12 gauge red wires in there is for the headlights.

 

Just Checked- the low beams are Sylvania Halogen the hi beams are bone stock filament. My last post I stated the lights no longer worked - which why (I think) several of you mentioned fusible Links. When I started it today they were working again so it looks like the switch (or whatever is shutting it down reset itself) I have the lights on now - hi and low) and so far after 30 mins not shutting off. That HD 6 connector plug by the hood alarm switch has seen its better days - gonna see if I can find them someplace.

 

Not sure what you mean by "bone stock filament" for the high beams. They were originally halogen trade #5001. That number should be on them. If not, they could be a higher wattage replacement.

The circuit breaker in the headlight switch is certainly doing what it is supposed to do--unfortunately it's not easy to determine if it's doing so when it should. While a few common multimeters can measure current up to 20 amps, most can only handle 10 and those above 20 tend to be quite expensive.

 

THe low beams have Halogen written on them- the hi beams do not - that is why I wrote/assumed they were not Halogen. I called Lectric Limited Trchnical Support (company that makes the switches for Corvette America and others) a 1981 corvette should have NON HALOGEN headlights for low beams and HALOGEN for Hi-Beams - I have just the opposite. I told them I can't find any low beam NON HALOGEN - they in essence said tough luck - the system normally draws 14 AMPS - they put a 16.5 AMP CB in the switch BECAUSE THAT IS WHAT THE SPECS CALL FOR. He believes my configuration draws more than that and that is why I have my problem. He has heard of many others who have this problem and he has no idea how they got around it. He suggested I get relays - have the headlight switch control that and the run a wire from the relay to the lights (through a CB) I am amazed at this response. They know you can't buy non halogen lights and that halogen lights draw more than what their switch is rated at YET they still make the switch the same way. AT A MINIMUM there ought to be a warning on the switch saying if you are using halogen bulbs you will have modify you cars electrcial for it to work.

 

I'm not sure about that amp rating (more on that later) but I would be very suspicious of your high beam bulbs. A rather popular substitution still suggested at this forum sometimes is to use extremely narrow beam 75W or 100W lamps that are actually aircraft landing lights.

I believe that the currently available high beam bulbs (trade #H5001) are 50W just like the originals.

As you were told the original trade #4000 low beam bulbs are essentially obsolete and difficult to find. The information I could find about them shows that they draw 67.5W with both filaments burning (as when high beams are on). The common halogen substitution lamp (#H5006) uses 75W with both filaments burning.

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Regarding amperage:

I believe that the original bulbs were rated at 235W total with all six filaments burning (switch set for high beam). 235W / 12V = 19.6 amps total current draw.

Using the common substitution for the low beam lamps it's 250W total or 20.8 amps total draw @ 12V.

Again, those wattage ratings are based upon information I can find now. I am not positive if they are the original wattage ratings. I do however believe that the trade number of automotive lamps includes wattage as a given so that say a #4000 from GE is the same as a #4000 from Sylvania. Change the wattage and the trade number also changes.

If the wattage ratings I've given are correct than it shouldn't matter which bulbs are being used as long as the high beams are #H5001 and the low beams either #4000s or #H5006s

That 14A (actual) 16.5A (circuit breaker spec) cited by Lectric Limited sounds suspect. The 14A is about what I would expect for the four additional filaments that burn with the headlights on high beam [I]but not including the low beam filaments that are still by design burning.

If they are quoting the original GM engineering specs for the switch circuit breaker then I cannot in any blame them for not increasing the capacity despite knowing that some of the original bulbs are nearly impossible to find. Why? Because the wiring sizes used are far from generous with regards to the amperage flowing through them. The single (one each side) low beam filament is OK for 18 gauge wiring but the 16 gauge used for the high beams (after the dimmer switch) really pushes what is considered "acceptable".

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Back to your specific problem:

I believe that your high beam lamps are highly suspect and may well be high-wattage replacements that were never intended to be installed. If so that alone could account for your failed headlamp switch, highly stressed looking connectors in the circuit, etc.

I suggest getting a pair of H5001s (easy to find) to see if the circuit breaker still trips.

 

!) I don't blame them for not increasing the amperage of the CB BUT I do think they have a moral obligation to tell the buyer that this switch you just bought probably won't work with your vehicle, alternative wiring will be needed. (This based on them claiming their CB is 16.5A and your own research stating 4 elements along would be more than that.
2) THe hi beams are definitely NOT HI Intensity. They are not as bright as the low beam when it is on hi and don't seem to have a white a light (halogen) as the low beam. Even so I seem to recollect this problem first occuring when I was driving and on low beam. Regardless as I am at crossroads on this issue so I'll get a new pair and see what happens.
3) I have a new switch coming today. AFTER I install the new headlights - if it still fails I will install that to see if the problem persists. IF so, will put in a relay AFTER the HL switch but before the dimmer switch witha a fuse and HOPEFULLY solve this problem once and for all

THANKS for all the help you have given so far. It is obvious you know your stuff and have a REAL COMMITMENT to this forum and this wonderful vehicle.