Oil pressure gage
Thread Starter
Instructor
Joined: Jan 2004
Posts: 242
Likes: 4
From: deland fl
Oil pressure gage
Hi Guys-
I know this has been discussed here at great length but I haven't been able to search and find it. My oil pressure gage, 1975 L-48 built to 383 with zero miles on rebuild, goes to 20 psi at startup and won't move from there regardless of rpm changes. Also stays at 20 psi when engine is shut off. How would you check the gage and the sending unit ? Or is this normal?
TIA
Larry
I know this has been discussed here at great length but I haven't been able to search and find it. My oil pressure gage, 1975 L-48 built to 383 with zero miles on rebuild, goes to 20 psi at startup and won't move from there regardless of rpm changes. Also stays at 20 psi when engine is shut off. How would you check the gage and the sending unit ? Or is this normal?
TIA
Larry
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Not normal at all. Take the wire off the sender unit and ground it. The gauge should go all the way to full pressure or beyond. If it does you have a bad sender. If not either the wire is broke or the gauge is fried.
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
Great question, and one I would like to know the answer to as well. I've got a 79 with the stock L48 and I recently pulled mine out to put the white face gauges on it. Since doing so, it stays at 20 as well. It did hit the 40 mark prior to this. Wonder if I fried something?
Thanks.
Thanks.
Thread Starter
Instructor
Joined: Jan 2004
Posts: 242
Likes: 4
From: deland fl
This is exactly the info I was looking for.
I'll give it a try in the morning. I hope it's a sending unit problem, I really don't want to tear the console apart again. It was a breeze taking it apart but a real PITA putting it back together.
Thanks again !
Larry
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
I'm gonna assume I fried mine. I had accidentally connected shorted the unit (I think) by mistakenly unblocking the contacts by swapping out the ones used on the alternator gauge. If that makes sense... Its not hard to do, believe me. Even with pictures, I put it back together wrong and kept blowing fuses. My guess is that is what fried it.
I guess I'll be replacing that now too...
I guess I'll be replacing that now too...
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The electronic oil pressure gauge is basically a fuel gauge with a different face. Yes there are more windings inside the gauge and yes the oil pressure gauge has a quicker response time from these differences. However, the oil pressure gauge works on the same scale as the fuel gauge. 0 ohms – no oil pressure and 90 ohms max or 80 lbs on most electric gauges. .
Ok. . . .How does this effect you! Test the sending unit ohms output! Easy to do with a multi-meter! This will tell you if the dash unit is reading correctly.
0 = 0 ohms.
40 = 45 ohms
90 = 80 ohms.
Mia, if you shorted something out pull the cluster out of the car and check the 90 ohm resistor between the poles on the gauge! You can do this with the same multi-meter. Usually this is what will blow before the gauge tanks.
If you have continuity across the resistor then it is good and the gauge is fried. If you don't have continuity then you need a resistor. If you test it for continuity and it is good, test the resistance and see what you get, it should be close to 90 ohms.
I have good tested used gauges if you do find this to be the problem. 75-82 oil pressure gauges are 50.00, Resistors are 10.00. Neither is on the web site, but if you need them just give Norm or Tommy a call to order 800-588-3883.
Willcox Inc.
Ok. . . .How does this effect you! Test the sending unit ohms output! Easy to do with a multi-meter! This will tell you if the dash unit is reading correctly.
0 = 0 ohms.
40 = 45 ohms
90 = 80 ohms.
Mia, if you shorted something out pull the cluster out of the car and check the 90 ohm resistor between the poles on the gauge! You can do this with the same multi-meter. Usually this is what will blow before the gauge tanks.
If you have continuity across the resistor then it is good and the gauge is fried. If you don't have continuity then you need a resistor. If you test it for continuity and it is good, test the resistance and see what you get, it should be close to 90 ohms.
I have good tested used gauges if you do find this to be the problem. 75-82 oil pressure gauges are 50.00, Resistors are 10.00. Neither is on the web site, but if you need them just give Norm or Tommy a call to order 800-588-3883.
Willcox Inc.
Last edited by Willcox Corvette; Apr 22, 2009 at 12:24 AM.
