gauges/wiring???

[rowicki]

OK here's the deal. I bought a 74 k5 and, like a retard, didn't even look inside before hand. I got it home and realized the gauges didn't work. So I checked all the fuses and realized one was blown. So I swapped it had had all continuity but still no gauges. So I went and bought a coolant temp gauge and hooked it up to the existing wiring. It worked, but read wrong. So I returned the gauge thinking it was defective. Next one did the same thing. So I ran a wire straight from sending unit to gauge and it works fine. I'm kinda lost because if it had continuity wouldn't it work the same?. I'm hoping that this might be the answer to all my gauge problems....thanks in advance guys. Kinda lost here. Definitely hate wiring crap!

 

[Fordum]

Continuity, just means that the wire is good. Not what the resistance is. Offhand, it sounds like a bad ground.
The other gauges may have been trying to use that sending unit for a ground, which would create other paths and change the effective resistance.

Is the new gauge you bought a factory type? If its an aftermarket, it might not be right for the system.
I'm pretty sure there is not an actual standard for the range of resistance for the sending units.
Probably most all the GM are the same, but aftermarket and other makes would be different.

 

[chulisohombre]

Most of the gauges work off ground. One wire on sending unit is ground and one is output from the sending unit to the harness and to the gauge cluster. Some are grounded through the sending unit itself and will have a single wire. There is probably three connectors its got to get through til it his the Guage. Maybe start there by disconnecting and cleaning the harness connections. I had to do that to my firewall harness to get it to get a good connection.

 

[blazer74]

At the cluster harness connector there are 2 black wires one for ammeter and 1 for the cluster grounds. The ground is at one of the ends of the rectangular plug make sure it has not pulled back a little in the connector. Clean the the connections and look to see if the plastic cluster circuit is damaged.
Put a meter on the ground wire at the connector and check for continuity to body.
That ground also runs to the ac/heater panel for the light, if that works assuming that's connected correctly your ground should be good to the body.