My oil pressure gauge was pegged at one point in time.

After a few hours of working on the issue I finally found the solution. Here are some things for you guys to check for:

1. On the back of the gauge there is an "I" terminal. Connect that to a hot terminal on the key switch. Here is the tricky part, make sure there is a plastic washer between the casing of the oil pressure gauage and the ring on the end of the wire that attaches to the "I" terminal.

2. On the back of the pressue gauge there is a "S" terminal. Make sure there is also a plastic washer on this "S" terminal that keeps the wire ring that you slide over it off of the case of the oil pressure gauge. This wire that attaches to the "S" terminal goes to the fuse box and from there it goes through the fire wall and to the sender unit. It is very important that this wire does not touch a ground. At the end of the wire put a connector that has a hole in it to the wire. Attach this to the sender unit.

**If your pressure gauge is pegged to the right this will be the cause of it. This wire cannot touch a ground on the frame or on the gauge itself.

3. There is a gound on the back of the gauge. Run a wire from this terminal to a good ground on the frame.

When you put the gauge back in the dash make sure that the "I" terminal and the "S" terminal do not touch any metal on the dash.


LAST NOTE: Some oil pressure senders do not match up with the oil pressure gauge. If you have mismatched sender and gauge it could cause your gauge to read incorrectly.

Also, some oil pressure senders are rather poor in their make-up. Some are either on or off which is not good for a real gauge but it acts more like an idiot light. In other words if your gauge is always reading 'average' you might have one of these senders.

 

87-up trucks are wired like that. I don't know when they quite doing that, if ever. I would assume some of the later trucks got away from this mess but I am not sure.

 

Good point.

Over on another forum some guy figured out how to make some of the Ford gauges read accuratly. Pretty smart guy if you ask me. He started off by connecting his air compressor to the oil sending unit and he took readings at every 10psi up to 70psi which was the max of his compressor. Then he did graphs and posted those. Then he compared that graph to an autometer (I think it was autometer) and the auto meter sender was much more consistent.

Some Ford engineers got word of what he was doing and they actually wanted to change the sending unit so that it would read more correctly. Rumor has it that upper Ford management said "No".

I think the reason why was because of people in general. If a person buys a car and the oil pressure reads average then there is not much to complain about. If you stick in an accurate gauge and it reads high or low then you have warrenty work on your hands or maybe a mad customer.

To bad. Don't get me wrong. Ford builds some fine cars and trucks. Some are the best in the world. However, they should be built for the more intelligent car or truck owner. Quality will survive. In other words put in a gauge that reads the right pressure. On the fip side of the coin, they know what they are doing. Ford is the strongest American auto maker.

 

The point is really moot as far as I am concerned, because most of the gauges that are wired like this from the factory have "L NORMAL H" on the face anyway. That tells me nothing. I always install a aftermarket gauge on a engine that I am concerned about reading the actual pressure. And that goes for the temp gauge also.

 

Also, if you're driving down the down and your pressure drops to zero, you have mere seconds to shut down your engine before you could lose your engine. In this case a warning light or buzzer might be better. I check my gauges upon start up but don't check all 7 of them while driving down the road very often.

 

Do youhave any pictures of the terminals to attach the wire to. I have a oil pressure gauge pegged at high and need to fix.

 

This thread is almost 7 years old and he has not posted since 2014. You also have not listed the year, model, engine type of your truck.

 

I'm sorry I know the post is old. I have the same problem my oil gauge is pegged at high I know it's a short of some kind I think in the gauge cluster. I am looking for a solution. I have changed the oil sender. The gauge sometimes but rarely reads accurately. I know the gauge is a on off switch so high can not be a reading I have a 2003 Ford F-150 with the 4.6 v8 any help will be much appreciated.

 

I would take the wire off the sending unit(really a switch) and with the key on engine off, ground the wire to the engine block, and then unground it while someone is watching the needle in the driver's seat. If the gauge reacts to this, your new sending unit/switch is bad, or you put too much tape/sealer on the threads and it's not making good contact to the engine block through the threads of the switch.

If the needle does not react to this, you have a cluster problem. Sometimes the take it apart and put it back together trick works if it's a corroded or loose connection somewhere.