Multi meter reading help

[tkjeeper]

Hate to do this, I've been absent for so long and I think this is a newb question. Please go easy on me.

My 98 cherokee, which happens to reside at university with my daughter now, had a gauge issue this weekend. I cleaned the battery terminals, didn't help. It was registering properly on my DMM, 13.8 ish while running, but the concern is when off, it was still reading 12.99. Is that normal? I took the battery in to have it tested, it was very old, and it failed so we replaced it. Installed and ran a while and the in vehicle gauge was still wonky. With the new battery in the reading are the same, 13.8ish running, but 12.9 off? I'm assuming the guage is pooched and I'm trusting my DMM. Is there anything I missed? Is 12.9 when off normal. Sorry for the newb question, and thanks for the help.

 

[WB9YZU]

Reading 13.8V when the Jeep is running is normal.
12.99V when freshly turned off is also normal.

So what's this gauge problem you are chasing?

-Ron

 

[tkjeeper]

That's the issue, my gauge inside the vehicle is reading about 12 when I start it, but doesn't rise when running, actually after a few minutes it drops to just over 9 and stays there. Everything runs fine, just took it out for a test run. I was worried the in vehicle gauge was right and it was my alternator. I know the dash gauges are very inaccurate. Thank you so much for the quick help

 

[WB9YZU]

I'd check grounds from the battery, and the frame to the engine.

I would also check the positive auxiliary lead for good connections at the Battery and the Fuse Block under the hood.

In that year, the voltmeter is an indicator on the Cluster via the internal Bus to the PCM. Translated, the PCM sends data to the Cluster, which indicates the voltage.

Probably nothing to gut real upset about, but the ones on my XJ's have usually been accurate except when not charging, then they drop to zero.

 

[tkjeeper]

Thanks so much

 

[weebur]

Hate to do this, I've been absent for so long and I think this is a newb question. Please go easy on me.

My 98 cherokee, which happens to reside at university with my daughter now, had a gauge issue this weekend. I cleaned the battery terminals, didn't help. It was registering properly on my DMM, 13.8 ish while running, but the concern is when off, it was still reading 12.99. Is that normal? I took the battery in to have it tested, it was very old, and it failed so we replaced it. Installed and ran a while and the in vehicle gauge was still wonky. With the new battery in the reading are the same, 13.8ish running, but 12.9 off? I'm assuming the guage is pooched and I'm trusting my DMM. Is there anything I missed? Is 12.9 when off normal. Sorry for the newb question, and thanks for the help.

Yep, as stated there's probably nothing to worry about, but I'll add that when you take a battery out of a vehicle (or leave it in for that matter) and put it on a charger it will always read over the normal fully charged voltage of 12.6 right after charging. If you wait a couple of hours it should drop down to 12.6 or so. See if yours does.

There is a battery temperature sensor under the battery attached to the battery box that helps regulate how much current is sent to the battery. Not all dash gauges in the XJ's are inaccurate, all of mine are stable and accurate, all of the time. It would bug me if they weren't.

 

[tkjeeper]

If I were driving it regularly it would bother me too, but for now, I'm reassured that she shouldn't get stranded from this. Funny enough, the old battery registered a fail at the place I took it for assessment. Convenient for them, lol. They showed me the printout. I'm not concerned, the battery was very old anyways. If it's a bad ground that's causing issues with the gauge only, I can track that down when it's warmer out! My Cherokee burned to the ground via gas thief a couple years ago, I sure miss this community. But I'll be back. 3 teenage daughters are a handful. Any other ideas as to where to look for this gauge ground issue is much appreciated. I love you guys, thanks.

 

[Rush Power Systems]

Another possibility, the data lines can be effected by too much RF noise, if you have old plug wires and/or plugs you could have too much RF noise. Could be an issue in the wiring as well but most likely in the gauge cluster if you have around 14 volts when the gauge is showing low voltage, $100 at the dealer and you will know for sure.

 

[hubs97xj]

When my alternator was on its way out, the gauge would drop to ~9V whenever the voltage at the battery dropped to 12V or less. Whacking the alternator with a wrench would un-stick the brushes, and it would charge/read normally. It ran fine for the week or so I tolerated it, but it was not charging normally, and that's what the gauge was telling me.

It's true that the gauge isn't terribly accurate, but I wouldn't assume everything was fine.

 

[tkjeeper]

When my alternator was on its way out, the gauge would drop to ~9V whenever the voltage at the battery dropped to 12V or less. Whacking the alternator with a wrench would un-stick the brushes, and it would charge/read normally. It ran fine for the week or so I tolerated it, but it was not charging normally, and that's what the gauge was telling me.

It's true that the gauge isn't terribly accurate, but I wouldn't assume everything was fine.

I hear ya, but even when the cluster gauge would drop to 9 V, my dmm was reading 13.8 or so while running. I will keep an eye on the alternator. ty

 

[87manche]

belt tension correct? I had the same thing happen to me on an 01 because I didn't have the belt tightened properly.

I'd also be tempted to pull the cluster, inspect and clean the connector. They have issues.

 

[Boatwrench]

What you describe was the first indication of an intermittent problem with my 00XJ prior to all the guages going dark. I haven't done the repair yet but removing the cluster and cleaning the contacts will help.

Here is an informative thread regarding the main ground wires.

and another that is for 97-01 XJs

 

[tkjeeper]

What you describe was the first indication of an intermittent problem with my 00XJ prior to all the guages going dark. I haven't done the repair yet but removing the cluster and cleaning the contacts will help.

Here is an informative thread regarding the main ground wires.

and another that is for 97-01 XJs

Holy crap! Mr. Boatwrench? What did I Do to deserve this? Back in the day, I had 5-90's wiring upgrade. Haven't done that on this jeep. Thank you for the help guys. I think I will check the belt tension first, then, go after that cluster, then track the engine compartment grounds. Nice to chat again BW!

 

[tkjeeper]

Re: Multi meter reading help, SOLVED!!!

Ding Ding Ding Ding!! We have a winner! 87Manche is the winner with the belt tension theory. Thanks so much for all the help from everyone. I just got back from a LONG and beautiful trip to North Carolina, long for me from Canada, 14 hours! Had a great soccer weekend. Took Monday off to recover so I decided to tackle this issue again. Took the cluster off, it looked perfect, checked the belt, loose. Tightened up, gauge back up to normal. Love visiting your awesome country, thanks for the help all.