... on a '81 Chevy PU.
Only one outta 10 or so is very weak suggesting bad ground, rest no worky. Now where would I find the cluster ground? Wiring diagram is not specific to ground location.
Second suspect would be bad printed circuit board. All worked when put away a year ago.
New light switch. New wiper switch w/ light works fine.
Didn't pull cluster yet before calling it a night.
TIA
Check resistance between the ground wire on the cluster connector and the chassis.
Please don't take this wrong, but at least half of the dim clusters I fix are because people don't realize there is a rheostat to turn them down...You have cranked the knob, right?
Those resistors have been known to go bad. For a long long time the circuits were wired battery > rheostat > bulbs > ground. At some point (and sorry I don't know when) a lot of manufacturers went to battery > bulbs > rheostat > ground. Knowing which 'side' of the bulbs the rheostat goes to is a big help diagnostic wise. A digital volt meter will tel you if the rheostat is good; connect it across the rheostat terminals and then move the knob, you should see the resistance change as the knob moves. If it doesn't or the reading shows an open circuit, there's your problem.
But, based on your description that only one out of 10 works and that one's weak I'd check the grounds again very carefully. Typically 1 out of 10 working and that one weak tells me the bulb circuit is getting a 'feedback' ground through something else, like a gauge etc. That indicates a ground wire somewhere is inadvertently not connected.
Try this: with the cluster out so you can see the back of it, plug it in and then turn on the dash lights. Find the power wire for the dash lights and verify you have +12v, you can use a test light but typically a voltmeter tells you more. If you don't have battery voltage or better, go back through that part of the circuit and look for bad connections etc.
If you do have battery voltage, find the ground terminal for the dash lights and use a jumper to temporarily ground that to the body. If the lights brighten, there's your problem; check the grounds.
If it doesn't brighten, next you'll need to jumper across the dash light terminals on the rheostat. If the lights brighten, there's your problem. If it doesn't, that's gonna be a head scratcher.
New light switch and swept the rheostat. The new wiper switch w/ light is bright. Was going to clean all cab to chassis grounds (I still will) but the wiper light being that bright would point to cluster ground. Found one ground under dash last night and cleaned before calling it a night.
Time to pull the cluster.
Trucks been sitting a while, s'pose I'll hafta go over all ground connections.
This truck needs to go, sooner rather than later.
Did the mice get to it?
Nick_Comstock wrote: Did the mice get to it?
E36 M3, don't say that, but if... that could possibly be old damage. Little berkeleyers cost me an entire summer patching the firewall, blower box and cowling after they stripped the firewall insulation and stuffed it into the heater/ vents and cowl, like a rodent condominium. That blocked the drains and rotted out them out. Had to pull the front clip for repair access.
I keep the cab and dash stuffed w/ dryer sheets now.
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