|Originally posted by fierofool:|
Usually, a bad ground can cause the gauge to peg. To test this, when you have a known good sender, unplug the harness with the ignition on and watch the gauge.
Iffy plug or wires can do same. Iffy gauge and resistor can make problems too. Resistor is on the back of gauge hidden inside of dash.
gauge clips holding the bolts and dash "board" on back of dash can cause problems too. The clips may look good but make crap connection between gauge and board.
Can short the gauge to ground for 0 on gauge I think.
But make sure of is sender pin.
Others is Fuel pump and short 1 pin of them to ground blows FP fuse at minimum.
cave page has pin out for 88 plug is why to read even w/o "upgrade" for older cars.
Multiple Senders doesn't fail this way.
Plug/wire w/ problem can wreck them.
Example: If shorts FP switch wires to sender wire can wreck sender and maybe gauge.
Bad sender sender ground is hard to do but possible.
Check sender Ω. 0Ω = 0 pressure, 90Ω = max pressure. 45Ω is half scale.
Should be 0Ω between pin A and engine w/ engine off.
If true use a needle poke thru Tan wire plastic should be same connected to sender.
If true wiggle tan wire watching Ω meter. should stay at 0Ω.
Check other senders pin A to metal bottom for 0Ω.
It all are open, wiring/plug problems are very likely.
Sender part can't handle power on FP switch and fries fast when has plug/wire problems.
Gauge "reads" sender's 0 to 90Ω.
Gauge pegs if sender or wire is disconnected.
Gauge can read off, way off, or even peg if sender wire is iffy or body to engine grounds are iffy.
Temp gauge should read off to way off too when has engine ground problem too. Volt meter in GT cars can have same plus iffy HL lights etc.
Sender wires go thru C500 and more on the way to the gauge. Any plug along the way can have a crap connection cause a peg gauge.
[This message has been edited by theogre (edited 02-07-2020).]