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Battery, alternator, loads, or some of all 3?

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
My 87 Renix, 4.0, Waggy is back on the road :D (AW4 swap finally done). It has been in my shop for about 6 months now. I put a 20 minute head light load, followed by a full re-charge on the battery about every 6-8 weeks, then disconnected the battery posts in between during the 6 month down time. It starts the jeep fine, but at idle, with headlights on, brake lights, back up lights and AC on max, and radiator e-fan on, it starts draining the battery, reading about 12.6 V after 10 seconds of peak load.:rattle:

At first the battery was reading 12.25 V this morning, No load engine off, before running it again. Started up fine, got up to about 14.05 V peak with no loads (it is usually about 14.7 V peak, no load). Cranking voltage has stayed above 10.1 volts at all times in about 8 restarts, even with the head lights and radiator e-fan running while cranking. ;)

I cycled the battery several times today, load, crank, run recharge and the final engine off no load battery voltage was 12.75 V (.50 volts higher), but It still drops to 12.6 volts at idle in gear, brakes on, in reverse, back up lights on, head lights on and radiator efan on with AC at Max AC, so at that point it is discharging the battery. Note the idle is at about 550 rpm at that point, in gear, but running smoothly.

When the voltage was only 12.25 at the beginning today, when I started all this testing, I figured the battery was weak, on its last legs (Autozone Red top, about 2-2.5 years old) and that maybe it was not giving the alternator enough juice at full load for the alternator to put out max power.
Not sure if the alternator is a 60/65 amp, or 100 amp. It is OEM stock, but this Waggy has electric windows, locks, seats, etc.

IIRC, I found out last year that the 100 amp and 60-65 amp look almost exactly alike? So with spares floating around, hard to tell what I have. One question I have, is what should it have stock, 87 Wagoneer, 4x4, with trailer tow package, D44 rear....the works, what size alternator was stock?

How can I pin down the problem?
 
I'm pretty sure that all the stock AC equipped XJ's had 100amp alt.
 
5-90 would probably know. Other than trying to look for a PN. I don't know.
 
No one has any ideas on my other question?

How can I pin down the problem?
 
Fresh data. I let it set 24 hours.

Battery was 12.51 V, no load, engine off.

Turned on the Radiator fan, and voltage dropped to 12.01 V

To me that is a battery with problems, does everyone agree? That is a big voltage drop for just the radiator fan load I think!

With the radiator fan running I cranked it up, minimum cranking voltage was 10.1 Volts, and it cranked fine and started fine, so the battery seems OK on the high amp draw, but not on the high voltage end, which IIRC can affect the alternators performance when all the loads are turned on?

5-90??????

Charging voltage with only radiator fan on was 14.41 V, so I guess the alternator is OK, on the peak charging voltage, low amp load side of the issue (but It was lower yesterday, never got over 14.2V).
 
My XJ do not charge at 14+ voltage except in the extreme cold in the Northern states. During the summer in the South, the highest voltage I have seen is about 13.5 when the engine is cold and lower when it is hot. My XJ have the battery temperature sensor.

I am on the opinion that there is nothing wrong with the battery. However, if you think it may be a problem, get it load tested with a good instrument set to the battrey amperage and put the load on over time.
 
Fresh data. I let it set 24 hours.

Battery was 12.51 V, no load, engine off.

Turned on the Radiator fan, and voltage dropped to 12.01 V

To me that is a battery with problems, does everyone agree? That is a big voltage drop for just the radiator fan load I think!

With the radiator fan running I cranked it up, minimum cranking voltage was 10.1 Volts, and it cranked fine and started fine, so the battery seems OK on the high amp draw, but not on the high voltage end, which IIRC can affect the alternators performance when all the loads are turned on?

5-90??????

Charging voltage with only radiator fan on was 14.41 V, so I guess the alternator is OK, on the peak charging voltage, low amp load side of the issue (but It was lower yesterday, never got over 14.2V).

Mike, you have the data you need to troubleshoot, and I know you're better than that. I'd be only mildly surprised if you came up with the same diagnosis I did (I'm just not going to hand it to you. Yeah - call me "House" and get it over with.)

You can apply your information rather more thoroughly if you find my writeup on troubleshooting primary electrical - I think it's in OEM Tech.
 
The drop to 12.1 volts with just a 20 amp load from a radiator e-fan was a dead (LOL) givaway. Took Autozone all of 60 seconds of testing to confirm it was bad.

What was interesting is that it started a Renix easily and quickly in just about 3 seconds with no problems, and held 10.1 volts while cranking with the Efan also running. Batteries on their last legs can be very deceptive.

Got a warranty swap deal and upgrade to the gold top Duralast, 8 year battery. 740 CA IIRC. The stock was like 490 IIRC. The red top I replaced was 540 CA.

Hopefully I can move on to the Enviro-Gestopo inspection next and get the old sticker replaced.
 
WTF NOW!!!!!:rattle:

I swap the battery, test the electrical junk, looks good. Time for dinner, shut it down, climb out and find 4-5 quarts of brand new T-fluid all over the driveway, looking like somebody just murdered the damn thing, from the AW4 I just swapped out!

Jessh, GMAFB!!!!:smsoap:

New battery is holding 14.45 V at idle with a decent load on it, but I still need to up the alternator output if I run everything, in Reverse at idle. I did get the reverse lights working again.

I think it may have a 61 amp alternator on it. Will check it later, but I can live with it the way it is for now.

Looks like one of the T-fluid lines came loose at the Transmission. I used new plastic clips, but one must not have taken a good grip. I could see a round clear/white o'ring looking part under it in the puddle. At least I hope that is all it is.Too much fluid, too fast to be anything else IMHO. Spread out the floor dry, will recheck it tomorrow.
 
My XJ do not charge at 14+ voltage except in the extreme cold in the Northern states. During the summer in the South, the highest voltage I have seen is about 13.5 when the engine is cold and lower when it is hot. My XJ have the battery temperature sensor.

I am on the opinion that there is nothing wrong with the battery. However, if you think it may be a problem, get it load tested with a good instrument set to the battrey amperage and put the load on over time.

All my measurements were with a meter at the battery. Where are you measuring? 13.5V at the battery, engine running, with no loads indicates to me that 1/2 of the diode set up is dead in your alternator!

What year is yours? Mine are Renix years.
 
HOUSE!!!!!!:twak:

LOL

Should have known you were a House fan too, LOL.:laugh3:



Mike, you have the data you need to troubleshoot, and I know you're better than that. I'd be only mildly surprised if you came up with the same diagnosis I did (I'm just not going to hand it to you. Yeah - call me "House" and get it over with.)

You can apply your information rather more thoroughly if you find my writeup on troubleshooting primary electrical - I think it's in OEM Tech.
 
All my measurements were with a meter at the battery. Where are you measuring? 13.5V at the battery, engine running, with no loads indicates to me that 1/2 of the diode set up is dead in your alternator!

What year is yours? Mine are Renix years.


I have always felt a little jealous when I hear others talk about 14+ volts measured at the battery of their XJs. I also measure the voltage at the battery. The only times I have seen 14+ volts is when I am in NY or CT in the winter. Also while working in Iowa and Ohio during the winter and that is only first thing in the morning. My XJ is on its third battery. The first one came with the XJ at 135,000 miles and died a few months later. The second died about 2 years old. I went out of the country for 18 months and came back to find it was beyond resuscitation. The alternator I have chanced from the 90+/_ that was OEM was replaced with one from a WJ which is 135 AMPs. Both alternators reached the same maximum voltage and settled there.
My XJ is a 1996 bastard child having a build date of June 1996.....one of those that you never could quite figure if the replacement parts should be from a 1995 or 1997 year model. I disconnected the the battery temperature sensor once. 20 miles into the trip the CEL was illuminated. About 80 miles later the engine sputterd to a stop on I-75 doing close 80 MPH. All I did was to re-connect the sensor and all was good again in XJ land. I did see 14+ volts then on the dash guage. (I live in Miami and use I-75 to go to Fort Myers where I worked for 6 months).
 
I think the voltage regulator is in the PCM in the 1996 models. The Renix era VR is in the alternator itself. That might make a difference.
 
HOUSE!!!!!!:twak:

LOL

Should have known you were a House fan too, LOL.:laugh3:

Yah - I didn't get interested until about the third time someone compared me to House.

Then I watched the show - and I wasn't insulted. I thought the comparison made perfect sense. I'm somewhere in between Greg House and Perry Cox (Scrubs) anyhow, so that's just about right.

TANGENTIAL RESPONSE - 1984-1986XJ used the Delco 10SI/12SI alternator, internally regulated. 1987-1990XJ used the Delco CS121/CS130 alternator, internally regulated. 1991-2001XJ used the Nippondenso alternator, regulator in the PCM.

You can bypass the PCM regulator and install an external, but it will throw a code if you do it, and it won't stay cleared. It's a "hard" code, and will light the CEL/MIL as well.

(I know the House reference was kinda hokey - but I've seen you help someone else with this sort of thing a couple of times before, so I'm not going to hand it to you. You're too close to the problem - just step back, take a deep breath, and look at it like it's not yours. It will make more sense then, if it hasn't already.)
 
I think the voltage regulator is in the PCM in the 1996 models. The Renix era VR is in the alternator itself. That might make a difference.


It is PCM regulated.
I have grown accustom to seeing the guage below 14 volts and have come to accept it as ok since I do not suffer from dead battery syndrome. I would like to get in there armed with my CD shop manual and an OHM meter and take a look at the ignition and voltage sensor lead but that is not on the priority list for now.

An OHM test of the battery temperature sensor my help to shed some light on things. I have seen the test procedures and reading for a hot or cold sensor in the manual.
 
My brother, who passed away last year, was an MD, psychiatrist, and had a PhD in Nuclear physics and material science from Rice. Watching House is like watching him in the old days. CRAZY and funny all at the same time.


Yah - I didn't get interested until about the third time someone compared me to House.

Then I watched the show - and I wasn't insulted. I thought the comparison made perfect sense. I'm somewhere in between Greg House and Perry Cox (Scrubs) anyhow, so that's just about right.

TANGENTIAL RESPONSE - 1984-1986XJ used the Delco 10SI/12SI alternator, internally regulated. 1987-1990XJ used the Delco CS121/CS130 alternator, internally regulated. 1991-2001XJ used the Nippondenso alternator, regulator in the PCM.

You can bypass the PCM regulator and install an external, but it will throw a code if you do it, and it won't stay cleared. It's a "hard" code, and will light the CEL/MIL as well.

(I know the House reference was kinda hokey - but I've seen you help someone else with this sort of thing a couple of times before, so I'm not going to hand it to you. You're too close to the problem - just step back, take a deep breath, and look at it like it's not yours. It will make more sense then, if it hasn't already.)
 
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My brother, who passed away last year, was an MD, psychiatrist, and had a PhD in Nuclear physics and material science from Rice. Watching House is like watching him in the old days. CRAZY and funny all at the same time.

Sorry for your loss.

Funny how some people can be. Our orthopaedic surgeon is Dr. Ronald Joseph, Ph.D., M.D - started out as a Boston cop (of all things!) got his Ph.D. in Epidemology, and taught at Temple while he was doing med school. Highly motivated Boston Jew with a severely warped sense of humour (makes him easier to deal with.) Still sounds like he moved out here from Boston - last week (he's been in private practise out here for thirty-six years.)

My D.O. works out of a clinic in Los Altos - the owner of the practise is Rudolph Orson Waiton, M.D., D.O., J.D., physician, surgeon, FAA Medical Examiner, and Gawd knows what else - his office is literally wallpapered with degrees & certifications!

My wife had a gyno who was an M.D. and a J.D. as well.

Some people stack up degrees like trading cards - and they use them! When I was in school this last time, I was on a track that would have gotten me four degrees in six years - all practical subjects (MET with several emphases...)
 
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