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1975 Dodge w300
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Discussion Starter · #1 ·
Problem with dash lights, when dash lights on all of the gauges peg to max, dash lights off, they return to normal

All of the exterior lights, signals, work and light as they should.
When I turn parking or headlights on, the two signal indicators and high/low beam indicator come on and stay on.
all dash lights work and when i dim them to off, the gauges return to normal.

Am i correct to assume the gauges are being grounded by dash lights?
whats the logical way to approach this one?
thanks for looking.
 

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that would also be my thoughts , the next model's headlamp switch has a ground wire attached to it ...
 

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1975 W100 Power Wagon Adventurer Sport 318 727 NP203 3.55
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dodge82273 said:
that would also be my thoughts , the next model's headlamp switch has a ground wire attached to it ...
now you have my interest what is the ground wire supposed to be for and will the earlier connector still fit on top?
also look at the filter capacitors on the back of the circuit board they are old enough that one could have shorted.
 

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radio interference caps can be discarded .  its been so long I had a dash out of a pre 79 model I do not remember particulars .... some one else ? 
 

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'79 Macho 360 Magnum, Comp 480 cam, Hughes springs, 650 Thunder AVS, Pertronix Flamethrower ignition
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If the problem just showed up makes me be suspicious of the headlight switch also.
 

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1975 Dodge w300
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Discussion Starter · #7 ·
Yup. just came out of nowhere. I've tried playing with switch and no change, I tapped on dash and got it to stop but quickly returned. Its a very low mile truck with a good original unmolested harness. The only thing not orig is the voltmeter I added. I'm going to check where I tied the light into the fuse box to make it dim with dash lights.
Ammeter is bypassed.
If one of the dash lights was shorted, I would think I'd have a light out somewhere, but every light works. If a short in headlight switch, wouldn't you expect a light somewhere would be out? The ground being supplied to make gauges peg must be supplied by a fault in the illumination circuit.

Am I correct that gauges will go to max if grounded? or will they go to lowest reading?
I suspect something fairly simple, I'll advise progress as I dig deeper, weather permitting.
Thanks for the feedback thus far.
 

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'79 Macho 360 Magnum, Comp 480 cam, Hughes springs, 650 Thunder AVS, Pertronix Flamethrower ignition
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If it is the switch, playing with it won't help as it is most likely internal. If you (or someone else) has done some modifications to the wiring make sure your connections are good (grounds, 12v connections, soldering, wire, etc). 
 

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LOL thumpin dash and it works fer a short while ? a loose / bad ground / shorted printed circut board . contact / email member  "Dodgeboys" get a wire diagram of your years dash from him .. pull the dash cluster and look for common ( 1 ) problem to all dash illumination and the gauges are 2 different circuts , they must be shorted , or the ground is missing for the lights ... and its just a back feed.
 

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the gauge voltage regulator that plugs in the back of the dash might be part of your problem.
 

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1975 Dodge w300
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Discussion Starter · #12 ·
Had a minute to look at this again today. First thing I did was reach up under the dash and wiggle the plug that feeds the back of dash.  A little flicker and the lights and gauges acting normal.

But... now the signals dont work, yet the emerg flashers do.

Guess I'll have to pull the dash cluster out and have a better look at it. Maybe i'll get lucky and just have to clean up the contacts a bit?
 

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treewtreehuns said:
Guess I'll have to pull the dash cluster out and have a better look at it. Maybe i'll get lucky and just have to clean up the contacts a bit?
Yes.
I made a habit of putting a dab of dialectic grease on all contacts on my truck.
It makes it easier pulling apart later too.
 

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1975 Dodge w300
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Discussion Starter · #14 ·
Finally got a chance to take the cluster out and have a look. It is the connections at the gauge cluster but not plug to the pins but the pins are all loose where they mount to the printed circuit board.One pin came out with the plug.
Anybody ever fixed this one? I see some pricey used ones out there but they may have same problem, and besides that, mine is near mint in appearance.
Would there likely be anyone who can restore this type of thing? Thinking i'd rather pay for a good fix than an old worn part.
thanks guys
 

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The pins likely can be soldered. You just have to be careful & not get 2 or more "connected".

Bucky
 

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Yes, they can easily be soldered.
 

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1975 Dodge w300
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Discussion Starter · #18 ·
thanks guys, wasnt sure if i'd melt something if soldered. they sure are a cheesy method of attachment and wont survive many connecting and disconnectings.  Ill let you know how it goes.
 

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well over DO it and yeah ya could melt something LOL clean is important .
 
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