73 Barracuda Temp/Fuel only going 5mm or 1/4 way up - New sendings installed

[Cliff_rogers]

We have diagnosed all gauges work except the Temp and Fuel. We checked using the many sending unit checks on the web -  we then found out it was the sending unit on both, we changed both and both worked last weekend. Come this weekend and we decided to put everything back and noticed the gauges weren't working accurately. Both only go up about quarter way or 5mm up and stay stagnant. We changed the instrument voltage regulator and still they only went to 5mm or 1/4 way. We checked continuity and we are getting power to the violet, black and dark blue wires, as well as both ALT wires (red and black), fuses have been checked especially the 5th and 6th fuse. Any suggestions?? I know we are nearly there I just don't want to get auto electrician to do a diagnostic that I have already done etc.

Your help would be much appreciated. Finger crossed its a quick fix. Thanks all. 

[dodj]

Come this weekend and we decided to put everything back and noticed the gauges weren't working accurately.

What do you mean by 'put everything back'? What was different between last weekend and this weekend?

[1970 RT Challenger 1970]

How much fuel in in your gas tank? Full or 1/4 Full, or don't know?

[Cliff_rogers]

When I replaced the faulty fuel sending unit it was about 3/4, car hasn't been used since it was replaced so it should be 3/4 still.

When I was mentioned put everything back, I was referring to putting the instrument cluster, gauges and wiring it all up as per originally before I did my inspection on the gauges.

[Rich G]

Disconnect the sending unit and ground the wire. The gauge should go all the way up. That should eliminate the gauges. Always check your grounds

[Cliff_rogers]

Re: Disconnect the sending unit and ground the wire. The gauge should go all the way up. That should eliminate the gauges. Always check your grounds

We have tried that, gauges all work. We can definitely eliminate that one. cluster is also grounded when we connect everything up.

[jason340]

Can you check the ohms at the tank sending unit and then check it at the gauge. That should tell you if you had a bad wire, pinched, skinned ect.

[dodj]

We have diagnosed all gauges work except the Temp and Fuel.

So just one (oil pressure) worked. That would prove your regulator is ok.

Re: Disconnect the sending unit and ground the wire. The gauge should go all the way up. That should eliminate the gauges. Always check your grounds

We have tried that, gauges all work. We can definitely eliminate that one. cluster is also grounded when we connect everything up.

Well if you get full deflection when you ground it and only 5mm with the sending unit....it's your sending unit. New or not.

unless...

Did you do the grounding test with the gauges installed and in place? It would be possible to knock wires off installing the cluster.