questions: voltmeter and oil pressure gauge

Just took my '03 C2 on a 900 mile trip. Happily, it ran like a champ the whole way (and a shocking 31 MPG). The voltmeter reads 14. Does that indicate anything at all about the health of the battery? I noticed the upper end of the gauge is 16. I've owned the car for 2 years, so really don't know anything about the battery (other than the car fires right up, even after sitting for 10 days). Cruising along at 3000 RPM, the oil pressure is always very close to 4, with very minor fluctuations (ie. maybe .2 bars of variation). Every once in a while, for a period of a couple minutes, it would become more jumpy, fluttering over a range of maybe .7 bars (ie. jumping around between 3.8 and 4.5). What might cause that behavior of the gauge? Thanks!

Volt meter is normal. oil guage is probably the sending unit

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I've read sometimes it's just corrosion on the contacts. Worth giving it a cleaning before replacing the sender?

For the cost and additional 15% more work i would just swap the sender. Plenty of how to threads out there.

My oil gauge did the same thing. I cleaned the contacts and that worked for a day or two. Change the sender. You will need a crow foot wrench set up with long socket extension(s) to reach the nut on the sender from the bottom. Going from the top there is no room to get a wrench in there. 14V on the voltmeter gauge while the engine is running means your alternator is charging properly.

Thanks for the replies everybody. I've watched videos and read threads about replacing the sender. One issue - it seems many people needed to grind down the 19mm crow's foot to use it. I once had a bench grinder, but no longer do. Can one be purchased that doesn't need to be modified? Thanks.

I didn't modify the 19mm crow's foot. It takes a bit to get the wrench on the nut and then remember which way to turn the ratchet (because you are doing this from the bottom). You can only get small turns. Once loose you can unscrew it from the top. The job was a minor pain, but not really difficult.

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Any chance you could measure the thickness of your crowfoot, or tell me where you got it? I assume the thickness varies from vendor to vendor. Thanks.

There is no chance I can measure the thickness with any degree of accuracy, but I bought a set at Lowes, probably Crapsman, oops, I mean Craftsman. Open the rear lid, look on the right hand side top of the engine. Reach in there and carefully disconnect the wire leads. The sender is probably original, so the leads won't want to come off. I don't remember if I removed the top of the air filter box first for a better sight line. After the leads are off jack the rear of the car high enough to lay under the muffler, use jack stands to secure. You have to move the exhaust heat shield out of the way a little to see and reach up there with the extensions and crow's foot (without the ratchet). After you get the crow's foot on the nut attach the ratchet and turn clockwise (because you are doing this from the bottom). Mine took a couple of good hits with my hand on the ratchet to loosen it. Once loose it was very loose and easy to unscrew from the top. Thread in the new one from the top, attach the leads, and tighten back up from the bottom. It doesn't have to be super tight. I did not look for any torque spec, just tightened by feel. I started the car, checked for leaks, and took it for a test drive. Instead of reading high all the time or reading 0 the gauge behaves as it should. The biggest pain for me was getting the crow's foot completely on the nut. It felt like it grabbed, but slipped off several times. At one point I got it securely on, stood up to look from the top, then bumped the extension going back on the ground and knocked it off the nut. After playing that game a few times I was able to loosen it and swap it for a new sender. Also use caution when reaching in from the top to thread in the new sender. You don't want to drop it and have it disappear somewhere in the engine bay or crash to the ground.

Before I bother with replacing the sender, can anybody state what "normal" behavior of the oil pressure gauge is? If I'm cruising along at a constant RPM, should the reading be rock solid? If not, what variance should be expected? Thanks.

With the engine fully warm, cruising 40 - 60 mph, it should read around 3 bar. The pressure will go up when accelerating. Cold start expect to read 4 or just under 5 bar. The pressure will read lower as the oil warms up. Hot idle is around 1 bar. Notice my figures start with "around". These gauges are not that accurate and lots of cars read a bit differently. Bottom line is if your gauge pegs at 5 and then randomly drops to 0 your sender is bad.

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Thanks, but my question isn't about what the reading should be at certain temps/RPMs. My question is: in a stable state (warmed up, constant RPMs), how much variance from second to second is expected? How much variance indicates the sender is going bad?

the sending unit can be reached from the wheel well with the wheel removed but i find it easier to reach it from the engine bay. 15 min job. I laser cut a custom crows foot at work that worked great. If you want to use it i can mail it to you if you mail it back when done. The easiest solution is to buy a crows foot and modify it.

When the sending unit is close to failure you might see the gauge suddenly drop to 0 when u hit a bump or brake hard, and then comes the heart stopping warning message in the center dial.

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Thanks! If I decide to replace it, I will be in touch.

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Yeah I'm not seeing anything like that. I'm wondering if what I'm seeing is indicative of a sending unit on its death bed, or if it's normal.

The gauge isn't accurate or responsive enough to track movements every second. Most of the time the symptoms of a bad sending unit are either the gauge is pegged at 5 bar when driving and up to temperature or the gauge suddenly drops to 0 after starting or while running.

Just replaced the oil sender, and am happy to say that the flaky readings at the gauge are gone the oil pressure reading is now very consistent. Interestingly, the gauge now shows a lower pressure than the old one. The previous one showed around 4 bars at 3000 RPM, where the new one shows about 3.2.