- Location
- MilkyWay Galaxy
Yes to both questions. If it was a 60 amp alternator, it puts out only 30 amps. If you draw 50 amps, 30 amps comes from the alternator, and 20 from the battery, slowly killing the battery.
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Voltmeter dropping? Check gauges?
- Thread starter DanMan2k06
- Start date
DanMan2k06
NAXJA Forum User
- Location
- Damascus, MD
Ahhh I see. Is there any way that it could be slowly dying (the alternator). It seems to be an intermittent thing. Could the diodes be loosening or poorly connecting, so that half the time I have full power, and sometimes only 50% power? It did it once yesterday, out of the 5 times i drove the car.
- Location
- MilkyWay Galaxy
Yes, if the carbon brushes are wearing out, or the diodes can intermittently open when they get too hot. All solid state electronics can come and go, work one minute then not the next as it gets too hot, then cools off. They eventually fail completely.
Mine always slowly drained the battery at night when the head lights were on. Headlights were the extra load that drained the battery. As the battery drains it's voltage excitation to the alternaotr drops, which further drops the alternators output. The AC, and extra Efan load with AC running, cycling, can add to the load, when running.
I always watch my head light and ash light intensity for early detection, early warning of imminent alternator failure.
But, an exposed hot wire, rubbing the frame intermittently can do the same thing, draw too much current, dragging the system voltage down.
Mine always slowly drained the battery at night when the head lights were on. Headlights were the extra load that drained the battery. As the battery drains it's voltage excitation to the alternaotr drops, which further drops the alternators output. The AC, and extra Efan load with AC running, cycling, can add to the load, when running.
I always watch my head light and ash light intensity for early detection, early warning of imminent alternator failure.
But, an exposed hot wire, rubbing the frame intermittently can do the same thing, draw too much current, dragging the system voltage down.
DanMan2k06
NAXJA Forum User
- Location
- Damascus, MD
Ok. That definitely makes sense. I think my lights put the thing over the top. Ever since I added the 6 driving light bar up top, it's been making strange noises and pulling the voltage (on the gauge) down ever so slightly. I have the Suck Edition, which only comes with a 90 amp alternator like most. The lights add another 40 amps to the system when on, along with upgraded high wattage headlights, and a small amplifier in the rear. Looks like it's time for a Durango alt.
- Location
- MilkyWay Galaxy
SE edition eh! LOL.
You got easy, my Nissan diesel XJ only has a 50 amp alternator. It is a special Hitachi alternator with a vane/oil flooded vacuum pump on the back side that supplies the brake, and AC controls vacuum. Only upgrade I have found is 60 amp!:tear:
You got easy, my Nissan diesel XJ only has a 50 amp alternator. It is a special Hitachi alternator with a vane/oil flooded vacuum pump on the back side that supplies the brake, and AC controls vacuum. Only upgrade I have found is 60 amp!:tear:
WB9YZU
NAXJA Forum User
- Location
- Madison, WI
Bad Alternator. Just replace it.
As mentioned, On OBDII compliant XJs the PCM controls the voltmeter and when the voltage drops below a certain level, it fails the guage and pops the Check engine light on.
Ron
edit: The first time mine did this, it was intermittent. Then it failed completely.
As mentioned, On OBDII compliant XJs the PCM controls the voltmeter and when the voltage drops below a certain level, it fails the guage and pops the Check engine light on.
Ron
edit: The first time mine did this, it was intermittent. Then it failed completely.
Last edited:
- Location
- MilkyWay Galaxy
Hold on, the 87-90 Renix has the voltage regulator and diodes in the alternator. OBD-I or II moved the voltage regulator to the PCM, if I recall correctly, so be sure you figure out which is bad, and make sure it is not wiring failing in between them!
DanMan2k06
NAXJA Forum User
- Location
- Damascus, MD
Well it finally took a dump last night on the way home. I used to be able to get it back working after a few restarts, but this time it just dropped to "zero" everytime. By the time I got home, my lights were dim and the dash was dimmer.
- Location
- MilkyWay Galaxy
PM 5-90, he knows if the 97 has a voltage regulator in the alternator or the PCM computer.
1)Did anybody ever get a VDC reading across the batt terminals running?
2) My portable alt checker at work always reads 1/2 the rated output of the unit when hooked up under the hood. I don't use that as an absolute - volts are more important as an indicator of proper function.
There are lots of lights hooked up? How many, what wattage, is there a separate harness, etc. Bolting up 6 to 8 150 watt H4's is going to double the load on a stock alternator and burn it out. Drains the battery dead shortly after.
2) My portable alt checker at work always reads 1/2 the rated output of the unit when hooked up under the hood. I don't use that as an absolute - volts are more important as an indicator of proper function.
There are lots of lights hooked up? How many, what wattage, is there a separate harness, etc. Bolting up 6 to 8 150 watt H4's is going to double the load on a stock alternator and burn it out. Drains the battery dead shortly after.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
It was already covered, its in the alternator.
- Location
- MilkyWay Galaxy
So what years did they move it to the PCM?
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
When they switched the voltage regulator to the PCM when they went with the HO in 1991 (OBD I).
- Location
- MilkyWay Galaxy
So your prior post is wrong?
I thought it was in 91, bit I only have Renix era jeeps, so I don't keep up and memorize as much on the later jeeps.
DanMan2k06
NAXJA Forum User
- Location
- Damascus, MD
So it could be the alternator OR the PCM??? I'm still leaning towards the alternator. I have:
(2) 55 watt fog lights,
(2) 100 watt Hella 500's,
my regular H4's which are 140/100 on a beefy harness,
and up top I have (2) 100 watt H3's,
and (4) 55 watt H3's.
When they're all lit up, it can be quite the surge.
(2) 55 watt fog lights,
(2) 100 watt Hella 500's,
my regular H4's which are 140/100 on a beefy harness,
and up top I have (2) 100 watt H3's,
and (4) 55 watt H3's.
When they're all lit up, it can be quite the surge.
5-90
NAXJA Forum User
- Location
- Hammerspace
OK - one more time for this:
1984-1986 - Delco 12SI with internal regulator.
1987-1990 - Delco CS130 with internal regulator
1991-2001 - Nippondenso open-frame (various sizes) with external regulator circuit in the PCM. This covers OBD-I and ODB-II - and it's pretty much a Chrysler standard these days (they quit using their own alternators years ago, and use either ND or Mitsu units instead. Some Bosch on high-output units.)
Since you have an external regulator, and they're actually not known for going bad, you have a few more connexions to check.
1) Go ahead and remove the PCM connectors (the 60-lead "harmonica" plugs) and blast them out with a good dose of electrical contact cleaner. Brake parts cleaner will serve in a pinch.
2) Check that all three (maybe four) of the wires going to the back of the alternator case have good mechanical contact, and that all of the ring eyes, studs, and nuts are clean. The battery output post takes an M6-1.0 nut, and I think the two field contact studs take either an M6-1.0 or M5-whatever (I don't recall the pitch for the M5 thread) nuts. A small brass brush works wonders - if you don't have access, use an old toothbrush and cheap toothpaste (rinse with contact cleaner) on the posts and a regular old eraser on the rings, so you don't remove material. Reterminate as required.
There will be three leads (output, field power, field ground) and may be four (ground lead attached to the alternator case.) Make sure all of the rings are clean, all of the fasteners are clean, and all of the terminations are good.
Check the main grounds - one will be back by the oil dipstick bracket (above and aft of the distributor. Clean it well - it tends to get oily) and the one on the fender liner (clean the contact patch on the chassis down to bare metal and apply corrosion inhibitor, like Gardner-Bender Ox-Gard. It's what I use, it's what I recommend, it's what I sell. NB: WD-40 has no RPT no valid electrical uses, despite what the label on the can or the display text may say!) It won't hurt to give the engine-to-firewall ground a seeing-to as well, but it's not as critical as it is on RENIX.
Verify any suspect voltage readings with a "known good" multimeter test, reading taking at the battery posts and/or at the alternator output post (best to check both - that can point something up. They should not differ by more than .1VDC - if they do, you have a dirty connexion somewhere.)
A fairly standard test to check the electrical integrity of the main connexions is to put one voltmeter lead on one part of the connxion and the other lead on the very next part (for instance, one on the battery post and the other on the clamp) and take a voltage reading - it should not be more than .1VDC difference. The same thing can be done using an ohmmeter - but remove power from the circuit first (not more than 2 ohms.) If the reading exceeds those specifications, take the connexion apart and clean it. Repeat for all of the exposed bits you see. The positive mains connections can be readily checked for a voltage differential - don't neglect the PDC to battery cable posts and such (post-nut, nut-lug. Two tests there.)
You can use corrosion inhibitor on most of the mains connexions (particularly the alternator, since it's low,) but make your own for the battery. Use four fluid ounces (one-half cup) of petroleum jelly and one and one-half tablespoons of baking soda (not baking powder!) For ease of mixing, heat the PJ gently in a double boiler and stir in the soda. Pour into an amber jar (if available) and paint on battery posts and clamps using an "acid brush." Discard the brush, store the remaining jelly in a cool dark place. Reapply at least annually, or after washing the engine bay or soon after deep-water fording. Likewise corrosion inhibitor on other connexions.
1984-1986 - Delco 12SI with internal regulator.
1987-1990 - Delco CS130 with internal regulator
1991-2001 - Nippondenso open-frame (various sizes) with external regulator circuit in the PCM. This covers OBD-I and ODB-II - and it's pretty much a Chrysler standard these days (they quit using their own alternators years ago, and use either ND or Mitsu units instead. Some Bosch on high-output units.)
Since you have an external regulator, and they're actually not known for going bad, you have a few more connexions to check.
1) Go ahead and remove the PCM connectors (the 60-lead "harmonica" plugs) and blast them out with a good dose of electrical contact cleaner. Brake parts cleaner will serve in a pinch.
2) Check that all three (maybe four) of the wires going to the back of the alternator case have good mechanical contact, and that all of the ring eyes, studs, and nuts are clean. The battery output post takes an M6-1.0 nut, and I think the two field contact studs take either an M6-1.0 or M5-whatever (I don't recall the pitch for the M5 thread) nuts. A small brass brush works wonders - if you don't have access, use an old toothbrush and cheap toothpaste (rinse with contact cleaner) on the posts and a regular old eraser on the rings, so you don't remove material. Reterminate as required.
There will be three leads (output, field power, field ground) and may be four (ground lead attached to the alternator case.) Make sure all of the rings are clean, all of the fasteners are clean, and all of the terminations are good.
Check the main grounds - one will be back by the oil dipstick bracket (above and aft of the distributor. Clean it well - it tends to get oily) and the one on the fender liner (clean the contact patch on the chassis down to bare metal and apply corrosion inhibitor, like Gardner-Bender Ox-Gard. It's what I use, it's what I recommend, it's what I sell. NB: WD-40 has no RPT no valid electrical uses, despite what the label on the can or the display text may say!) It won't hurt to give the engine-to-firewall ground a seeing-to as well, but it's not as critical as it is on RENIX.
Verify any suspect voltage readings with a "known good" multimeter test, reading taking at the battery posts and/or at the alternator output post (best to check both - that can point something up. They should not differ by more than .1VDC - if they do, you have a dirty connexion somewhere.)
A fairly standard test to check the electrical integrity of the main connexions is to put one voltmeter lead on one part of the connxion and the other lead on the very next part (for instance, one on the battery post and the other on the clamp) and take a voltage reading - it should not be more than .1VDC difference. The same thing can be done using an ohmmeter - but remove power from the circuit first (not more than 2 ohms.) If the reading exceeds those specifications, take the connexion apart and clean it. Repeat for all of the exposed bits you see. The positive mains connections can be readily checked for a voltage differential - don't neglect the PDC to battery cable posts and such (post-nut, nut-lug. Two tests there.)
You can use corrosion inhibitor on most of the mains connexions (particularly the alternator, since it's low,) but make your own for the battery. Use four fluid ounces (one-half cup) of petroleum jelly and one and one-half tablespoons of baking soda (not baking powder!) For ease of mixing, heat the PJ gently in a double boiler and stir in the soda. Pour into an amber jar (if available) and paint on battery posts and clamps using an "acid brush." Discard the brush, store the remaining jelly in a cool dark place. Reapply at least annually, or after washing the engine bay or soon after deep-water fording. Likewise corrosion inhibitor on other connexions.
DanMan2k06
NAXJA Forum User
- Location
- Damascus, MD
Awesome. Thanks Jon.
scully
NAXJA Forum User
- Location
- ma/nh border
wow. i gues ill go work on my dead alternator now.
muchos thank yous.
eace:
muchos thank yous.
eace:winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
My 2000 has a temp sensor under the battery that cuts the charge rate if it gets hot. If you have one too, that would be worth checking.
scully
NAXJA Forum User
- Location
- ma/nh border
ill check on mine too.
thanks bro
thanks bro
