Factory oil pressure gauge

[69SKCharger]

The issue ended up being a lose pin on the printed circuit board behind the instrument cluster. It wasn't getting a full signal from the sender (I think). I ran across this while making my own 5v regulator to replace the old mechanical one. I doubt that the regulator solved the problem since the other gauges work as they did before (minus the fluctuations).

 

[1970charger440]

I had some problems with my oil pressure gauge and figured it out with some help here. I rebuild my 1970 charger and in the process thought it would be a good idea to replace the oil pressure sending unit to a new shiny one. The new motor never had great oil pressure. I changed the pump with no different results. I started running thicker oil. It would read about 40 at start up, but struggle to keep 30 psi once warm. The problem bothered my and I was considering pulling the motor even though I knew the tollerances were good.

Someone suggested I put a mechanical gauge on it and sure enough it was reading 70psi cold and 60psi after warm. Whew! I didn't need to pull the motor and start an unecessary and expensive investigation. The previous motor had good oil pressure, so my focus became the sending unit. I researched the correct part number and then ordered a number of different new sending units. The results were all the same or no reading. So I dove in deeper. Auto part stores specified the Autometer 2242.

The sending unit needed to match the gauge in psi reading and have the correct ohms for resistance to that reading. The Autometer 2242 is for a 100 psi gauge and has ohms from 33-240. Those ohms do not work with the stock gauge and will barely register any oil pressure. After seaching for the ohm requirements for the stock gauge I learned it needed to be from 10-73 ohms. at 73 ohms the gauge will read "0" and at 10 ohms the gauge will read "80". The Autometer 2241 meets those exact requirements. I ordered and replaced and pressure came up to where it should be.

If you are running a rally guage cluster then you will need the 2241 sending unit (pressure switch) for an accurate reading. Hope this helps someone from the hassle I went through.