Took my '69 GT500 out today and it started doing something I've never seen before. Normally the oil pressure reads about 75 cold and keeps 40-50 when hot and the needle is real steady. Today I noticed it was about 30 cold and the needle wasn't steady. Cruising at 60 it was 40 but when I hit the throttle it got erratic and when to zero. Panic at first but noticed at the same time the ammeter was erratic as well. At idle both needles were erratic in sync. Is this a known problem? Ground or voltage issue? Any prior experience will be helpful before I start trying to diagnose it.
Quote from: jimhyc on July 19, 2026, 01:29:22 PMTook my '69 GT500 out today and it started doing something I've never seen before. Normally the oil pressure reads about 75 cold and keeps 40-50 when hot and the needle is real steady. Today I noticed it was about 30 cold and the needle wasn't steady. Cruising at 60 it was 40 but when I hit the throttle it got erratic and when to zero. Panic at first but noticed at the same time the ammeter was erratic as well. At idle both needles were erratic in sync. Is this a known problem? Ground or voltage issue? Any prior experience will be helpful before I start trying to diagnose it.
My first thought is voltage . Have your regulator tested.
Quote from: Bob Gaines on July 19, 2026, 02:37:56 PMQuote from: jimhyc on July 19, 2026, 01:29:22 PMTook my '69 GT500 out today and it started doing something I've never seen before. Normally the oil pressure reads about 75 cold and keeps 40-50 when hot and the needle is real steady. Today I noticed it was about 30 cold and the needle wasn't steady. Cruising at 60 it was 40 but when I hit the throttle it got erratic and when to zero. Panic at first but noticed at the same time the ammeter was erratic as well. At idle both needles were erratic in sync. Is this a known problem? Ground or voltage issue? Any prior experience will be helpful before I start trying to diagnose it.
My first thought is voltage . Have your regulator tested.
I replaced the regulator this spring. So that's probably a good place to start.
If you want one accurate and reliable, use a GR540 Motorcraft and install your tall cover.
Just my opinion.
The voltage regulator and the charging system checked out fine but found two other issues. I found the ground strap on back of the rt. cylinder head loose and the stud on the oil pressure sending unit was loose. I was able to tighten the stud without letting the post turn. The oil pressure gauge no longer erratic or dropping to zero.