1970 w-30 oil pressure guage wobbles alot up and down while driving. Very eratic at times. Any ideas why ???

 

Bad sending unit
Loose connection or intermittent wire break
Weak oil pump
Debris on the inlet screen (ie, pieces of plastic cam gear)

Given that the sending unit is a rheostat that gets dirty or corroded over time, that would be my most likely cause.

 

Sending unit new after market. Have old original still, may try that to see if there is a difference. Car only has 1200 miles, seams to get worse as car warms up. Pretty steady whn first started.

 

Seen several aftermarket senders do this last 30 yr or so. Had one in an 81 Pontiac Safari that regularly did this. Friend's 81 TransAM did this too. GM senders solved the problem.

Be glad it's not a 90s-later Ford. Their oil pressure gages do not read actual pressure. Only tells ECM that the engine has oil pressure and gives you something to look at. Lot of discussion about it on Marauder and F150 forums.

Owning both, I'd rather they did it like Chrysler did. Chrysler products had ammeter and temp gages, but retained an idiot light for oil pressure. Might not have had the cool factor, but better than a lying gage.

 

Had the same issue with my Rally Pac oil gauge. Ran through some checks to narrow it down/to feel confident were the issue was. In my case the oil gauge was bad, I replaced the oil gauge and worked fine..