Octania

Some Other Brand [71 Challenger] car, troubleshooting fun:


Fuel Gage
Assumeframe to batt (-) is ok, all else works.
At tank sending unit terminal 90Ω to frame
Gnd strap across rubber line intact
0Ω tank body to frame.
Wire from car shows ~5V DC, correctfor 71 Dodge’s gages' V. Reg’r.

At dash
VReg shows 12V in, ~5V out to all threegages, pulsed or AC says the consultant
Gages read ~13-15 Ω each one, no wiresattached
Grounding the tank wire makes Fuelgage read full


I surmise this means the sending unit (new, Chinese?) is bad.


TEMP GAGE
similar no reading
grounding wire at engine makes gage peg the needle, so gage and wiring intact.
Probably a idiot lite sender- 1/8 NPT unit.
infinite ohms at room temp, open circuit across the sender.


TACH
THREE wires on coil negative- WTH?
Two are gray
tach should be gray/red
Sending 12V in at dash end gets nothing at coil end. ???
consult manual.
Gray wire should be here at firewall.... EMPTY NEST, no wire there at all.
Aye, aye, aye.
Easy enough fix.


PS they use a BLACK wire for POWER, from alternator, to gages, etc.
Idiocy, that.

oldcutlass

Mopars work differently than our Olds's. Scroll down to the middle of the link page.
http://moparfins.com/Repairs/Fuel_Ga...uge_Repair.htm

m371961

I worked on Fords and Mopars from 60s to 80s. Olds certainly are different and were /are a learning gig for me. Worked on Internationals also. ALL their wires were black and numbered.

oldcutlass

Worked on airplanes, all the wires were white and numbered.

Octania

OK, but, to me, using black for a power wire in automotive applications is just not right.

thanks for the link to the gages issue, will ck that now. I believe we have all three problems nailed, as soon as parts arrive.

oldcutlass

Electrons are color blind, they simply don't care about wire color.

Levellord

The PO of my car seemed to own just black wires. He wired everything black, regardless of plus, gnd or signal. Already spended me a lot of "fun" :-\

oldcutlass

The advantage of them using black wire or any other color for that matter is that you can easily trace out non stock mods. I use Red wire for everything.

redoldsman

I always use red for power and black for ground. The others are usually yellow or blue because that is what I have on my bench.