voltmeter showing little or no positive voltage

[myoldjeeptruck]

I have noticed my voltmeter barely registering in the black range and going into the red when lights, radio,wipers are on,it goes into he black range when first started up.This is the second or third alternator installed,voltage regulator?is original;any suggestions?

[Eagle]

Get a multimeter and check it at the battery. The voltmeter in my '88 XJ reads barely above 12 volts during the day with no lights or accessories running, and has been like that for about four or five years. Tested at the battery I'm showing just about 14 volts with the engine at idle. Gotta be some voltage drop in the wiring to the gauge, but I haven't bothered to trace it down.

[702_MJ]

:hijack:

 

don't mean to hijack but i kinda got the same problem that has been buggn the crap outta me. My guage wiil read 14v, and only drop a little when i turn the headlights on or wipers and such. But when i turn defrost on, or the fan for that matter the gauge drops dramatically! Second alternator new battery, and still does it. could it be the same?

[mvusse]

The squirrel cage draws a lot of power. When I have the fan on full speed as well as the headlights, the alternator can't keep up at idle and voltage drops to the edge of the red zone after a minute or so. The moment the engine revs up just a bit because I'm starting moving again, it pops right back up to the middle. And the lights brighten noticeably. Old alternator did it till death wobble fried it's bearings, new alternator does it, battery is fine. And I have the high amp alternator.

 

I did find out the alternator output is rated at 2000 rpm. Don't know how fast the engine has to rev to spin the alternator at 2000 rpm, though, as I never measured the crank and alternator pulleys.

[702_MJ]

so is that like a common problem?

[Throttle_Jockey]

It could just be a gauge problem I put autometer oil,temp,and volts in mine and the volts not running show close to 13 and when running close to 15.

I had a chevy truck do the same thing before and it ended up being the gauge.Check the battery voltage with a meter and compare to the gauge

[702_MJ]

i always knew those gauges couldnt be trusted. Ill do that, thanks

[88XJSport]

http://www.jeepforum.com/forum/showthread.php?t=684375

 

Havent done it yet, but it looks like it would work.

[702_MJ]

Hmm i like the idea, I'm gonna have to try it one of these days. But its kinda confusing. Where did he hook up the hot ignition wire, i mean what did he splice into?

[ratrapp]

my 88 did this as well.when i upgraded to a cherokee tach style cluster my volt gauge reads much higher.it's still not 100% accurate but it's alot closer.

[jaekl]

Ditto here. Used to read a steady 14 volts and then started dropping fast. Reading at battery indicated alternator was working. I pulled the cluster and had full voltage at the cluster plug. Cleaned the contacts a little and meter went back up to 14 volts. It's falling slowly again, so I'll have to try better cleaning.