I have a 74 road runner with a 318 and I'm trying to figure out my temp and oil gauge. I disconnected the bulkhead from the engine bay side and noticed that the pins on the fire wall for both the oil gauge and temp gauge are continuous with each other (they are right next to each other). This cannot be right. Is there a simple solution for this?



this is a picture of the top two tabs (oil, temp) on the fire wall bulkhead. My dmm shows it being connected.

 

How did you test with your meter and what were the readings to come up with your conclusion?

 

I put my dmm on the continuity test, then put a probe in each slot like the picture and it beeped.

 

If you did this with the battery disconnected you would see continuity as each gauge will be tied together for a common voltage supply.

Try each one individually to ground and see what you have in ohms or O.L.

 

Oh okay, my battery was disconnected. Should i try it with it connected?

 

I measured the ohms for each and they were both around 54 ohms. Does that sound right?

 

I don't know, without a wiring drawing and knowing for sure the circuit it's impossible to answer.

Do not test continuity (ohms) with current applied (battery connected), you will damage your meter.

General stuff here. http://www.allpar.com/history/mopar/electrical2.html

You may want to try here: http://www.forbbodiesonly.com/moparf...l-amp-Ignition

If your not a member, they have more activity or you can search for an answer.

 

You are reading right through the gauges in a loop configuration. Power would normally go to the gauges and then make ground via the oil and temp sensors which are no more than resistors that change with temperature and oil pressure. What you need to do is check every connector on the firewall for continuity to ground which will indicate a short. Then check the wires from the engine connector to their very ends for continuity to the sensors. While your in there, spray and clean all of the terminals of the bulkhead connector with electro spray, blow dry and coat with dielectric grease then reconnect. It's important to have a wiring diagram or manual and do this diagnosis in the proper manner or you may cause serious damage. There should be no power on the system
and the gauges removed so you can check for continuity from the end of the gauge connector right through the connected
bulkhead connector to the very end of the circuit where it terminates at the respective sensors. If the sensors are the correct
ones and there is continuity then probably the problem lies with the gauges themselves. Keep in mind that you want to focus
on these particular circuit wires only which are terminated to variable ground via the sensors and it is important to know the
color codes lest you pick the wrong wires.