Tampa 928s

When I purchased this 82 the voltage gage did not work, all bulbs and other gages are fine. I disassembled the cluster and cleaned all the contacts and checked the resistor. The car is charging fine even at idle. I removed the gage provided a 12 v adj power supply to it and it works fine, my meter followed the gage level. My question is where does this alternator voltage come from. The WSM shows its in parallel with the tach and oil pressure gages. It seems it maybe an on board problem is there any specific spot to check on the foil board to look for a break?

SharkSkin

Did you clean the brass pins and the copper trace rings on the board where they make contact? With the cluster out it should be easy to see where the traces go.... It's not the common wire that's your problem most likely the ground.

Tampa 928s

Yes I did I removed the gage cluster two of the connections 4-nuts total were for the bulbs and one each for the oil and voltage gage. Did I miss something its odd all the other gages work fine.

SharkSkin

Yes, probably the ground as I suggested above. You'll have to trace/buzz the circuit out.

Tampa 928s

I found a broken trace between the oil and volt gage main post. I am getting a wire to connect them and test, my wife has my keys go figure. Funny thing it looked fine but it is open under the board I wonder how that happened.

michael j wright

on mine, I found a broken trace onder the little plastic oval insulator that is held down by the two nuts- resoldered and brought it back to life. also while i was there, i also used my DVOM hooked to the jump post and adjusted the variable resistor next to the gauge to set the neddle to read the same.

SharkSkin

Not a good idea IMHO, unless you have freshened up the wires between the gauge and the battery first as I describe here and here. If you have the gauge out, see how accurate it really is. Mine was so accurate I saw no need to adjust it, and with all of the wires between the gauge and battery cleaned up it reads so close it's a non-issue.

Adjust that pot to compensate for the bad connection, and someday you will inadvertantly bump that connection and you will be posting on here "My voltmeter reads too high, WTF!!!"

Tampa 928s

SharkSkin I saw your post on adjusting or not adjusting the trim pot. I have a variable bench power supply and verified it with my fluke it was spot on. Once I got my keys back the gage fired right up. One thing done several more to go.

SharkSkin

Nice to have another data point. That's about a half-dozen people now -- on and off the list -- who have told me their gauge was spot-on, only one found otherwise and that could have been from a PO moving the pot or the needle.

It's easy to blame the gauge -- that's what we see. Some say the voltmeters are notoriously inaccurate, but I have seen more proof to the contrary.

toofast928

This may be a funny question but has anyone tried bypassing the resistor? Wouldn't direct voltage give a more accurate reading?

SharkSkin

The resistor is unrelated to the voltmeter, and does not connect to it in any meaningful way. Its purpose is to guarantee a certain amount of current to the exciter windings in the alternator.

michael j wright

Adjust that pot to compensate for the bad connection, and someday you will inadvertantly bump that connection and you will be posting on here "My voltmeter reads too high, WTF!!!" [/QUOTE]

Yea your right about that, but from waht i've seen so far the PO has touched just about everything on this car in the wrong way. And when I pull the dash this winter to rework it, I will follow your steps in the links you posted then will have to re adjust to, to make shure it's not reading to high.