XJ /MJ realy dim lights and low volts

[Cabz]

Just figured I would see if anyone else has had and reparied this issue. Both my MJ and the daughters XJ run good and everything works well, at an idle during the day the volt meter is dead center . at night when we turn on the headlights the gauge drops a bit as it should . After about 15 minuetes of haveig the lights on they get very dim and the volt gauge now reads lower by a bit and if we turn on the heater fan or a/c on high the volt gauge drops to the red . I am figureing there is a bad connection or a large resistance in one of the wiring conections . we both have new alternators, headlight switches, batt cables and so on . the jeeps are both renix jeeps and I have pined all the fuse links and I am getting 13.5 volts out of them and 13.5 out of tha alt at idle even thought the gauge reads around 9 volts and the lights are dimm enough to make that look about right . so it sems as the issue is after the fuse links and before the fuse box .

 

any Ideas? has anyone had an solved an issue like this?

[mvusse]

On mine if I have the heater fan full blast together with the headlight on after a few minutes the volt meter is almost in the red and the lights ate noticeably dim. As soon as I touch the gas (and the rpm come up *just* a bit) the volt meter goes up, the headlights brighten and the fan runs faster. I guess we are pulling more amps than the alternator can supply at 12V while idling.

 

I also noticed when it is cold out (and by cold I mean cold, as in single digits Fahrenheit, not 50 degrees like they call cold in FL) at any rpm faster than idle the voltmeter is almost touching red on the upper end of the scale. I guess that's the cold messing with the voltage regulator.

[Cabz]

On mine if I have the heater fan full blast together with the headlight on after a few minutes the volt meter is almost in the red and the lights ate noticeably dim. As soon as I touch the gas (and the rpm come up *just* a bit) the volt meter goes up, the headlights brighten and the fan runs faster. I guess we are pulling more amps than the alternator can supply at 12V while idling.

 

I also noticed when it is cold out (and by cold I mean cold, as in single digits Fahrenheit, not 50 degrees like they call cold in FL) at any rpm faster than idle the voltmeter is almost touching red on the upper end of the scale. I guess that's the cold messing with the voltage regulator.

 

Yup it is pulling more amps , but why ? :dunno: It must be bad connection somewhere. , a bad conection will get hot and cause the circut to draw more amps . I am sure when new they worked just fine so age and weather are my best guess as to what has caused the issue Now I need the where :D

 

as far as the cold goes , I am a transpalnt new yorker , I know the cold you speak of

When it is cold out it drains the battery somewhat so the alt senseing this charges them hard till they come up to the right voltage and then settles out , that could also be the signs your batt is drying

[vzehler]

I was going to recommend new battery cables, but, considering the fact that you've already changed them I would just start troubleshooting the connections until I found the culprit.

 

Fact is, that my jeep is the same way. It doesn't get quite down to the red at idle but it's definately lower on the gauge then I would imagine it should be.

[Cabz]

Bump :D

[mvusse]

Mine is the new alternator. The bearings in the old one got toasted during a severe case of DW due to excessive (2" inches!) toe-in after installing a lift. Before it got killed, the old alternator never went that low, or that high in the cold. The new alternator does.

[Pete M]

I've had similar issues with various vehicles over the years. In the MJs it was either a bad alternator or bad connections with the main cables. Don't forget to check the grounds running to the engine block.

[tugalo]

Try adding an extra ground between the neg post of the battery and the front clip sheetmetal....also remove and clean all other grounds.

[BLHTAZ]

Try adding an extra ground between the neg post of the battery and the front clip sheetmetal...

I have heard that this helps with headlight issues from a couple other people too.

[Ed in North Ga.]

This has been drug over and discussed on about every forum Ive been a member of or read-

 

first- its very common for our volt guage to read low, even though the battery is showing 12.9+ and the alternator is running fine- almost ALL xj/mjs of the renix era and early chrysler era do this- the guage lies. There was a guy years ago who did a write-up on how to reroute a circut on the back of the circut board guage cluster so the volt meter shows actual voltage- because what we see, is downstream voltage.

The voltage shown is an after volt- after everything-lovely...antoher design brought to you by renix-

 

The easier way to get around this, is a simple voltmeter install- and ignore the dash meter. You`ll find a correctly installed meter will show a happy 12.9+ with everything running IF the battery is good and the alternator is healthy-

 

that said, we move onto those wimpy headlights. Renix era jeeps are known for wires...lots of them, and their long- long wires create resistance- long old wires create more- add some old crud in the connections, and that happy 12.9 volts becomes a liability- the more the accessory wants, the hotter the cable gets- and the less useable amps your going to have- intresting, yes? Cleaning the bulkhead connector is feasable in some situations...but it gets so old, and ya gots to have ittybitty hands....

 

you`ll not fix the heater/ac- its always going to go up and down with RPM when the headlights are on- weve tried- short of rewiring, its just not worth the effort.

 

you can fix the headlights, by wiring around them and using good quality relays on each side- use the original headlight system to trun the relays off and on- happy bright headlights are good headlights. Ive seen one that was wiried off the alternator, and mine was wiried off the battery for years-

 

Their renix jeeps- you have to work them your way, not try to fix them the "right" way-

[Cabz]

I have allready done all of those things :???: thats why this is such a pain in the arse.

the alt is putting out great . all the cables are new and all the connections are tight .

I even pulled the headlights and cleaned the plugs , I also pulled the headlight wire main plug and cleaned it . still dim as hell after a while . I even went so far as to pull the bulkhead connector and it is just as clean and pretty as the day it was built .

[Ed in North Ga.]

realize that its not like other vehicles- its not a semi-direct connection between the pull and the headlight. Its a long, winding, stupid way to wire headlights. Theres too much wire, and too many connections-shoot, it could be a bad slide connection on the ignition switch-

 

If you pulled and cleaned every connection, replaced every wire that had a little extra resistance on it, and regrounded a dozen times- those lights would be awsome!

 

since thats not going to happen- and if it did, I wanna watch- your best recourse is wiring around the problem-

2 heavey duty relays per side- wire to the battery- wire to the switched hi/low beam OR headlamp positive-

 

its not that much work- I ended up replacing all that wiring and putting on a set of PIAA`s off a 87 grand cherokee(wide batt lens)- it don't matter how dim the headlamps get, I got light.

 

you probably got some of that fine Ocala sand in there gobing up the works...the world has no idea what "powder sand is" until they get stuck in your neighborhood....

[icurunnin]

The voltage gauge is pretty darn accurate in mine. I run a digital volt meter they sell at auto zone that plugs into your cigarette lighter. This thing works great. I tested the voltage at the battery and then read the display at the meter and they were within 2 10th's of each other. I learned long ago to use one of these in ALL my vehicles. Nothing like being broke down due to a bad alternator or a battery going dead. I highly recommend this to everyone.

I use to go muddin alot in my trooper and would spit alternators out every two weeks, and this was with the alternator being placed on top of the engine (deep water and mud). I soon realized I needed something that told me something was wrong and this way I could get somewhere safe quick.

The meter's are only like $15 and have a back lit display and are well worth it :clapping:

[Ed in North Ga.]

The voltage gauge is pretty darn accurate in mine. I run a digital volt meter they sell at auto zone that plugs into your cigarette lighter. This thing works great. I tested the voltage at the battery and then read the display at the meter and they were within 2 10th's of each other. I learned long ago to use one of these in ALL my vehicles. Nothing like being broke down due to a bad alternator or a battery going dead. I highly recommend this to everyone.

I use to go muddin alot in my trooper and would spit alternators out every two weeks, and this was with the alternator being placed on top of the engine (deep water and mud). I soon realized I needed something that told me something was wrong and this way I could get somewhere safe quick.

The meter's are only like $15 and have a back lit display and are well worth it :clapping:

 

I ran my meter direct- simply because on mine (89) all the inside electricals are run through either the bulkhead or the ignition box switch on the lower column-(not the underhood ignition box)

if I remember right (and its been awhile) I think off the lighter I was showing 12.2, and direct I was at 13- very little difference, but still-it buggs ya!

I never did retest it after the first ignition switch went bad- might have been just that resistance throwing it off.

 

I did see a sweet stu-warner liquid filled mini guage years back- he installed it in the blank after removing the LED clock- looked nice!

I wonder how hard it would be to do a dakota digital dash in one of these.... :doh: