i've read a few thing in here about the voltage gauge reading low but havent really found a response of someone finding the issue. so when i start the jeep voltage will read around 14 on the gauage for maybe 5-10 min then it drops to about 12 or so if i turn on the ac it drops to like 10-11. it starts fine ive only had it a few days so i haven't done anything to check it out yet. im gonna check the grounds and see if i can locate the issue im also gonna take out the sterio cause it keeps blowing the fuse (maybe thats part of it). so any sugestions on other possible causes. it looks like a new alt and batt. but im not sure cables also look new 4 guage wire.

 

Before assuming you have an alt/battery/cabling problem, check the voltage at the battery terminals with a DMM when your gauge starts reading low.

 

for sure im gonna do that tomorrow .thanks if it ok what should i check next any suggestions

 

The regulator in that alternator (assuming its similar to the stock one) should be keeping the voltage at 14.25 volts (in theory) but as soon as the battery stops "asking" for more charging current, it drops a volt and a half or so until the next battery demand. Its normal. If it is always at the 14v and above, that means your battery is always asking to be charged and its on its way out. (again, still talking about that era jeep)

As for when you put a load on and the volts go down. that is also normal considering age. The factory wiring is pretty small and the load is usually felt on the whole system. Anywhere where the ground points are either dirty, corroded or just small, there will be a small drop of voltage at every bad connection. The end result will be read at the gauge. If you measure at the battery and compare with with your gauge, the difference is the total voltage lost between every bad connection between the gauge and the battery.

in short, your battery is OK and so is your alternator. Adding a new ground directly to the body and cleaning any other ground wouldn't hurt.

 

Ive had a similar issue. Cruiser54 has a good list of places in your engine to check for grounds along with improvement.

Ive,

-added another (thicker) ground wire from the factory gauge cluster to its ground under the dash for better connectivity. It also brightened my back lighting
-added another ground wire from the negative of the battery to the chase
-refreshed the connections at the battery, ground on the passenger side engine block
-rubbed away any paint that was under a ground connection, giving metal to metal contact.
-replaced the metal ribbon going from the top of the motor to chase with a thicker wire purchased from Napa
-and taken the gauge cluster out, cleaned all the connections, and cleaned the connections between the gauge and the battery.

I haven't solved it, but it has helped. I would check the battery and see what the system actually is reading when your gauge says your low. I ultimately plan on replacing the gauge with a Stewart Warner voltage gauge.

Good luck bud!

 

First thing to do on a Renix Jeep.


Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.
If you want to upgrade your grounds and battery cables in general, contact Jon at


www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 03-04-2013

 

Thanks good info

 

Good reading and preventative maintenance for your Renix here:

https://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/

 

thank you i went through all that i saw it before but didnt read all of it ill work on those electrical maintenance tips

also is what karl4X4 said how the system works i never herd of that before. from what i know the battery should be at 13-14 while engine is running right

 

A properly operating regulator will always keep the alternator voltage slightly higher than the nominal battery voltage. If it didn't the battery would discharge even with the alternator running. 10-11 volts is never normal unless you are loading the system beyond capacity or have wiring issues.
You really have to check the voltage right at the battery before deciding what the problem is. Faulty gauge readings are one thing, an actual low voltage condition is another.
If your battery voltage reads fine but the gauge is low (which I'm betting you'll find), check the grounds- starting with the instrument panel ground.

Stolen from Cruiser54 while he was sleeping:

Improving the Instrument Panel Ground
The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼" or 5/16" head on it.
This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.
The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.
Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.
Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.
**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
　
Revised 11-29-2011

 

Like a thief in the night, you are. LOL.

 

For me low voltage under load, (brights blower ect), is the first sign my belt is slipping.

 

so i tried a few things today been cleaning up electrical stuff n such and tried to get my dome light on noticed it was missing the fuse and replaced it but it blows when i push the switch for the dome light so im sure i got a short somewhere that i got to find probably why my guage is reading low? what cha think cruiser54 im gonna start with disconecting the radio

 

my dome light turns on with my headlight switch but when i push the dome light button it blows the fuse obviously there's a short where should i look for this or where would be a possible cause ?

 

would bad grounds, cause no turn signals?? Have changed ALL the bulbs, ALL the fuses, both flashers, the circuit breaker and the switch for turn signal... by the way its all on an 88 pioneer... the hazards work great, but the dash lights cut off and on when they feel like it...