Question about installing different gauges (fuel, Battery, Temp, Vacuum)

[Mickey7]

This is the last question for today...   I ordered the new plastic circuit board for the back of my instrument cluster and installed it.  The fuel gauge still pegs at full (I know the tank isn't full) and the alternator gauge barely moves out of the lower red portion, the oil pressure gauge seems to work but I would like to have actual numbers to look at.  I don't know if the temp gauge works.  How difficult would it be to add separate gauges for these functions? 
Mike

[LJ-TJ]

Ahhhhhhhh finally something I have a little experience with. I picked these insterments up off E-bay and Craigs list for a few $100.00 bucks. Granted I had to do it one at a time as I could afford it. There all Autometer. I here Stewart Warner are the best and must be because I found them disgustingly expensive.Plus Autometer are U.S. made and the stand behind their product. This is what I ended up with. I found I don't really have to take my eyes off the road while driving in order to scan the gauges and when something isn't right you notice it is a flash. Problem is I can't find the pictures I up loaded. Maybe someone out there more computer savvy than I can help you with the pic's. Hm?

[LJ-TJ]

Some times I never cease to amaze myself. I found this thread on after market gauges. D:oH!

http://www.classicwinnebagos.com/forum/index.php/topic,7201.0.html

[Rickf1985]

You might want to unplug the fuel gauge, it is pegged due to a short in the sender wire going to the tank or a shorted sender itself. More likely the wire. It is not doing the gauge any wonders keeping it pegged like that.

[DaveVA78Chieftain]

Rick,
I thought from 1965 to the late 90's GM used a 0 â€" 90Ω (0Ω empty â€" 90Ω full) fuel gauge setup so stuck on full would be a open in the wire, not a short.

[Rickf1985]

Could be Dave, I thought he said when he plugged in the dash it pegged.

[DaveVA78Chieftain]

He did. When you plug it in 12vdc, ground,and the sender are placed in the circuit so a open sender would then be seen.

[Mickey7]

Rick1985
Let me clear up the fuel gauge thingy...  It stays pegged no matter if it's connected or not.  I took the whole assembly out and it was pegged to full, well actually it was pegged all the way past full.
Mike

[Mickey7]

So should I remove the sending unit and test it or can I test it on the connectors on top of the sending unit in the tank? 
Mike

[Rickf1985]

You can test it at the connectors. If you get voltage from the sender wire then the gauge is probably good. If you have an electric fuel pump in the tank (you should) and it is working then the tank ground is good so at that point the sender is probably bad. According to Dave (and he knows his stuff) the gauge should read full when disconnected so if you short the connector to ground the gauge should go to empty. That would verify a bad sender. If you do not have an electric fuel pump be sure to check the tank ground and the little ground wire at the tab on the sender. I usually add a jumper wire with alligator clips to a good ground for testing.

[DaveVA78Chieftain]

I am passing on what I found elsewhere.

GM Fuel Gauge Troubleshooting

Troubleshooting video

Full = 90Ω (e.g. open)
Empty = 0Ω (e.g. short)

I have no clue what the meter would read (empty/full) if completely disconnected from the rig.

Tank to cowl connector:
Pink wire (circuit 120): 12VDC power to full pump
Black wire (circuit 150): Ground wire
Tan/White stripe (circuit 30): sender lead to gauge.

What could confuse you is the sender wire (circuit 30) from the cowl connector to the panel gauge is pink not Tan/White stripe.

Various resistance values

Chassis	Empty	Full
Mopar pre 1987	73Ω	10Ω
GM Pre 1965	0Ω	30Ω
GM 1965 - 1997	0Ω	90Ω
GM 1998 up	40Ω	250Ω
Ford pre 1987	73Ω	10Ω
Ford 1987 up	16Ω	158Ω

[CapnDirk]

So should I remove the sending unit and test it or can I test it on the connectors on top of the sending unit in the tank? 
Mike

I would remove the gauge and test it first, a lot easier.  At the web site dave gave you, hook up positive and negative to the B and C terminals with another 12 volt battery, (with gauge removed from cluster) and see if anything changes.  Than hook up another negative wire from the battery and touch it to A and see if anything changes.  If you want the best info on the gauge you could run A through a 100 ohm variable resistor (duplicating what your sending unit is doing).

Shooting from the hip here and an aging memory  .  But getting the gauge away from outside influence may reveal where the problem is.  You can also then see if you have 0 ohms of resistance (or close to it)  on the wire that attaches to the gauge from the sending unit.