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GMC CCKW 353 B2 - headlight help needed!


Peter4456
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I'm hoping that HMVF members can help me solve a problem with the headlights on my 1942 GMC CCKW 353 B2. It's been very well restored (not by me!) and I'd like to keep it as original as possible - it's still 6 volt, for example.

Recently, one of the sealed beam headlight units 'died' and it seems they're not easily available any more. Rex Ward was kind enough to suggest changing to the easily available Lucas LUB322 light unit and LLB423 light bulb and with a bit of fettling they fitted perfectly, are brighter and still look right! Sadly, in the middle of my celebrations, one stopped worknig and then the second one did the same. I've refitted the one good sealed beam unit and this doesn't work, so I'm thinking fuse / circuit breaker, but where is it? Do I have to take the instrument panel out to get at it? (I hope not!)

 

Any helpful ideas gratefully received!

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Peter,

 

As per original spec. there are no fuses, just various circuit breakers which are thermal trips, so they will re-set themselves after a short while. Are the new bulbs now blown or is it the circuit that's now at fault? I wouldn't just go by testing with the 'good' sealed beam, can you put a voltmeter across the terminals?

 

- MG

 

I'm hoping that HMVF members can help me solve a problem with the headlights on my 1942 GMC CCKW 353 B2. It's been very well restored (not by me!) and I'd like to keep it as original as possible - it's still 6 volt, for example.

Recently, one of the sealed beam headlight units 'died' and it seems they're not easily available any more. Rex Ward was kind enough to suggest changing to the easily available Lucas LUB322 light unit and LLB423 light bulb and with a bit of fettling they fitted perfectly, are brighter and still look right! Sadly, in the middle of my celebrations, one stopped worknig and then the second one did the same. I've refitted the one good sealed beam unit and this doesn't work, so I'm thinking fuse / circuit breaker, but where is it? Do I have to take the instrument panel out to get at it? (I hope not!)

 

Any helpful ideas gratefully received!

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Don't bother with sealed beams unless you're a rivet-counter: you can fit Wipac lenses with 6V halogen bulbs and built-in side lights. There is no reason why a properly set-up stock electrical system shouldn't be able to power them and you'll get way more light.

 

Incidentally, for one bulb to go followed by the other suggests something other than a circuit breaker.

 

- MG

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I'm hoping that HMVF members can help me solve a problem with the headlights on my 1942 GMC CCKW 353 B2. It's been very well restored (not by me!) and I'd like to keep it as original as possible - it's still 6 volt, for example.

Recently, one of the sealed beam headlight units 'died' and it seems they're not easily available any more. Rex Ward was kind enough to suggest changing to the easily available Lucas LUB322 light unit and LLB423 light bulb and with a bit of fettling they fitted perfectly, are brighter and still look right! Sadly, in the middle of my celebrations, one stopped worknig and then the second one did the same. I've refitted the one good sealed beam unit and this doesn't work, so I'm thinking fuse / circuit breaker, but where is it? Do I have to take the instrument panel out to get at it? (I hope not!)

 

Any helpful ideas gratefully received!

 

Peter

 

Also worth checking that the lamp unit has a good earth connection, have been caught out by this in the past.

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Hi

 

In a headlight unit is two light bulb elements.

To give you an idea of bulb or electrical issues have you tried switching the high beam to low beam or visa versa?

If neather works then the odds are earths, thermal cutout blocks, or a dry joint?

Your multimeter is the best tool to sort issues like this out, disconnect bulbs when trying to ring circuits out as this can give you false readings.

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The headlights are wired in parallel at the junction block on the driver side inner fender.

 

TM9-801 page 251 has the wiring diagram and is available here:

 

http://www.tm9-801.com/searchTM9/tm9_pages/316.pdf

 

There may or may not be a 30A thermal fuse at the rear of your headlight switch. Also if you still have condensers at the junction blocks they may have shorted out. I would disconnect them until you can rule out any other wiring issues.

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