I have another active post on low oil pressure, this dovetails with that...

I found out that the dash dinger goes off when you hit 10psi of oil pressure but I don't believe that I have that low of oil pressure. Unfortunately I have been unable to put a mechanical gauge on it as of yet.

This motor was replaced about 40K ago and ever since I have had goofy gauges. My voltage dips down slightly every time I use a turn signal or step on the brakes, it also jiggles around which it never did before. My oil pressure was fine one day and dropped 20 psi the next but the motor runs fine even when showing 5 psi of oil pressure. I replaced the sender and I disassebbled the gauge cluster, I even connected a battery charger to the battery with the motor running just for giggles and it made no difference

I'm wondering where the gauge gets its data, I wouldn't think that it is straight from the sender, otherwise how would it know to ding at 10 psi? Does the sender go to the ECU and the gauges come from there? Is there anything common with all of the gauges that can make then goofy?

Here'* the real kicker... at idle the check washer fluid and check gauges sometimes light dimly. sometimes as I rev the engine they get brighter. Other times thay are 100% out and the light dimly as RPMs increase. The oil pressure and volts seem to drop as RPMs increases which is exactly opposite of what should happen.

I'm befuddled... any suggestions?

Check all your battery connections on both ends of the cables. Check the ground bus under the front doors, https://www.gmforum.com/showthread.php?t=278980

I did replace the + cable going to the power center and I have cleaned all of the battery terminals at the battery. I was unaware of the ground buss, I will check that next.

Let us know how it turns out.

I just ran down to the garage and found both ground buss connectors. I cut off the original rubber tape and removed the buss bar caps, I pulled them both apart and they both looked like new! I cleaned both anyway and reinstalled them.... unfortunately no change.

If you had your engine replace 40k ago and it'* been doing it ever since, then I'm leaning towards a bad ground. Your engine has 2 of them. One on the front of the block right behind the starter(this is your battery ground) and another one on the back side of the block right next to the oil pressure sending unit. Check the one on the back. This one I believe is used for all the sensors.

I'm in agreement about something being odd here. Grounds and power. Take the grounds another step. Follow and clean where the negative cable attaches to both fenders. The post is about 1.5 feet from the front radiator support. ensure the battery cables aren't corroded under the boots.

Might be a bad cluster..but let'* rule out the rest first.

UPDATE: Installed a manual pressure gauge... I have 50 PSI at cold idle and it drops to 42 at hot idle. No matter how hard I pounded on the motor, I got no less that 20 psi in gear, at idle, and after an hours run.

A new twist, if I really put my foot in it the check washer light and check gauge lights still come on as previously mentioned, but as the RPMs get up there pretty high, it starts to miss. I'm convinced this is electrical of else I would just put an under dash oil pressure gauge on it and forget about it.

I checked teh ground near the starter but can't find another one that is supposed to be in the rear.

We have a BREAKTHRU!!! I knew that the alternator bearings were getting a little iffy so tonight I took it off and I figured that I'd get it tested before I put bearings in it. The alternator won't make more than 10 volts!!! I'm thinking that the gauges were whacky due to low voltage, at 10 volts who knows what kind of crazyness can happen.

I have a call into a friend, hopefully I will have a replacement tomorrow.

Glad you found it.