Oil Pressure Gauge

[bobscuda67]

Hey Guys, I'm having a problem with my stock oil pressure gauge on the rallye gauge cluster on my car. This year when I got it out the needle wouldn't rise up past 1/4 on the dial and it was always at 3/4 at idle. I checked it with a mechanical gauge and it's at 75 psi at idle.
So yesterday I got real ambitious and got the dash out and dissembled and what I found is the needle on the oil pressure gets caught on something. I took the gauge apart and the bimetal is nice and straight and the wire is good as it does move some.
It seems to me the stud on the bimetal strip gets caught in the groove on the needle arm on a burr but I cant see it. Is it just wore out and I'm SOL or is it repairable?
I've looked on Ebay and there's a few of them on there if I need to get another one.
Thanks

 

[RedFish]

Best to just buy another. I have rebuilt a lot of the gauges. Getting a somewhat fluid like needle movement is the most difficult part of it. This needle is extremely thin and weak aluminum. Steel pivot post passes through 2 planes of the aluminum. All of this and that link to the bi metal must be square, plumb, perfect. If you want to remove the screen, disengage the bimetal, use a new and sharp hobby knife, try to shave a burr from that slot before buying another... go for it. Slip a dental pic under it at pivot post to hold it up so a little pressure from hobby knife doesn't bend it there.
So beyond all that... Looking at oil, fuel, and temp gauges in a early 67 model, all 3 needles/slots were different. This early 67 oil gauge had a flaw in its design. Needle would stick, might stop short of home showing oil pressure with engine stopped. Not quite enough homeward/actually needle lifting force from the bimetal. So how they cured this... They used the temp gauge. Shifted its bimetal to a different position and distorted the hell out of the needle stops on the oil gauge screen to make the temp gauge serve as a oil gauge.
There is one of these gauges that will lock up at max position if needle stop isn't set to prevent over travel. I forget which one it is. Anyway... If/when a replacement rally oil gauge has the needle stops tweaked to extremes, no worries.

 

[bobscuda67]

Good info!
I have been sanding the slot a little top and bottom and the pin also with 2000 grit sandpaper. It seems to have helped some as the needle doesn't stick anymore like it did. I put two d cell batteries on it and the needle went to the half mark and returned back to zero. Did that a few times and it worked and didn't stick like it did before.
I did the same thing to the temp gauge and it went to the half mark too.
The oil and temp gauge lock up at the full position on my gauges.

 

[RedFish]

Good info!
I have been sanding the slot a little top and bottom and the pin also with 2000 grit sandpaper. It seems to have helped some as the needle doesn't stick anymore like it did. I put two d cell batteries on it and the needle went to the half mark and returned back to zero. Did that a few times and it worked and didn't stick like it did before.
I did the same thing to the temp gauge and it went to the half mark too.
The oil and temp gauge lock up at the full position on my gauges.

The needle stop should be set to prevent lock up but... you likely experienced this by moving the needle by hand. The bimetal beam bows as it heats so its length does get a little shorter. So same lock up may not happen with beam moving the needle. My suggestion from this point... Leave them be. Know that if you ever do short a sender wire to ground for test purposes, the movement just might lock up. Lets hope not. Good luck

 

[bobscuda67]

Thanks Redfish! I'll have to keep an eye out for one at the swap meets.

 

[RedFish]

Thanks Redfish! I'll have to keep an eye out for one at the swap meets.

Members here offer them in for sale section. Some have been tested. When the lens and matting frame are knocked away from the bezel and into these gauges it distorts the needles. If you see a tiny white spot at the base of the needle, a spec of orange paint jumped off. Dark brown color board on the back is extremely brittle. To run a 10-32 die over rusted or damaged post threads with your finger tips can be the most nerve racking thing you'll ever do. They aren't all junk. During 8 years and a few 100 gauges, I handled some crap. Again, good luck