Wiring Question????????

I just installed a Rebel Wire harness in my 54 chevy. Now when I turn the key to the "on" position both the oil pressure and fuel guages max out. I tried disconnecting the oil pressure sender and it had no effect. The fuel tank is not in the car yet so it's sender has never been connected. What did I do wrong? HAMB gurus help me out. This my first time rewiring a car and I am definitely no expert when it comes to wiring.

BTW these are new electronic guages and the car is 12volt with SBC swap

 

if the gas gage uses the orignal sender, then I would expect it to max out if the sender is not connected.

I have no idea about your oil gage, but since disconnecting it does not seem to affect things, maybe it's already disconnected?

Did you make sure to electrically ground the gage housings to the body?

 

I'm just shooting in the dark here but maybe this is normal, I am guessing that these are electronic gauges? I would leave it be, and when you hook up your sending unit, and fire the car up, if the gauges are still maxed out, then go from there...I have a hunch that your gauges max out in the "key on" position, to prove to the driver that they are functional, then when car fires, then the gauges go to opperating, just like when "dummy" lights come on before you start the vehicle... Are you running a computer? If you aren't running a computer, you can almays go to mechanical gauges....Just another option..

 

Are you sure its not the other way around. I think it would read empty when the sender lead is disconnected. It might just be that the gauges are wired incorrectly.

 

no, the early GM senders are 0 ohms (shorted to ground) when empty, and 30 ohms when full. When the wire is shorted, it reads empty, when it's disconnected, it reads past full.

But I have no idea if he has a gage that is design to use the original sender, probably not...in that case, shorted might make it read full, depending on what brand gages they are.

 

Thanks guys! To answer some of your questions. The guages are new VDO electronic guages. They are grounded to the body(I ran a single ground to the entire panel) Should I run individual grounds for each gauge? As for the oil sender I just asked for a sender from a mid 70's V8 camaro at the parts store. The motor is a carbureted Gen I SBC 350 crate motor.

 

Used to be that VDO gages required VDO sending units...what do the instructions for the gages say about what senders to use?

 

hmm I'll have to check that out. I did buy the VDO oil sender but it would not fit. It would hit the intake and not thread in.

 

The gas gauge will read over full when it doesn't have a ground to complete the circut. You could run a jumper wire from the sender unit mounting flange to the body or frame and turn on the key, the gauge will read as you raise and lower the float. Just a thought on the oil gauge sender. Did you use abunch of pipe sealer or sealer tape when you installed it? You may have insulated the sender from a good ground that way. I try to never use any kind of sealer for electric senders. One more thing, The oil pressure sender you bought may be made to read backwards of what your VDO gauge needs for a signal. Iv'e seen that before. The hotter the engine gets the lower temp the gauge shows. Get a sender from VDO and dont use pipe dope. **** 1 more thing,is your engine grounded to the body and frame? very important to do that. Normal Norman OK you do have the VDO sender,you might have a metric fitting. You will need to sort out the mismatch and get that VDO sender in. N.N.

 

use an ohm meter and check from the guages to ground to make sure they are grounded. i have heard of guages sweeping and going back to there respected position but never maxing out. i am guessing its bad grounding. i am not 100 percent sure though.

 

Use a br*** pipe ****** and a 90 degree br*** fitting to get the space you need to run the VDO sender.

 

Really!!?? Is this a legit fix? I never thought of that. Interesting idea though.

 

How many grounds do you have to the body, frame, and engine. It sounds like you wiring is looking for a good ground.

 

I have a ground going from the battery to a bellhousing bolt then from the same bellhousing bolt to the frame at a body mount.

 

Sounds like lack of a ground to me. Even though you grounded the panel, the gauges might not be grounded to the panel.

 

Are they all clean with no paint, rust, or rubber, in the way?

 

The gauges are grounded in series then to a bolt on the dash. I just ran a single ground wire to all the gauges.

 

use the correct senders for the gages. If you still have problems, let us know.

There are lots of different ways to make gages, and each requires a specific sender. I guess you didn't know that.

 

make sure all guages ground to that one ground check by ohm meter and then see what it is from guage to body ground

 

Run a ground wire to the body from the engine, and use the VDO sender. As others have said go to the hardware store and get some 1/8" pipe fittings to space it up away from the manifold.

 

I still have the VDO sender. I will get some fittings to extend the sender and clear the manifold and see what happens. Thanks a ton for the help!

 

Got some br*** fittings and installed the VDO sender. Now it works like a champ.

THANKS Squirrel and everybody else too!!