another RENIX no charge, low voltage thread.

But i have not found one like this. my new to me 87 4.0 5 speed is having an electrical problem. volt meter reads low, in the 9 volt range. headlights dim, ac blower slow, stalling, and other symptoms of not charging. across the top of my new yellow top i get 12.1 volts with the engine running or off.

my alternator tests good at the 2 local parts stores. i have read many posts that say the parts store testers can be inaccurate, so tomorrow I'm taking it to an alternator shop. i have none that were open tonight. It is a duralast gold (autozone's most expensive reman) that came with the jeep. i did not notice any loose, excessive corrosion or dirt on any connection while i was removing it. the belt was tight with no unusual wear.

I took the new yellow top to the parts store, they tested it and said it was fine. i didn't go to both stores with that, i figured if i had a factory defect they would detect it.

All of the battery cables show 0 ohms form terminal to their end point.

Let's assume the alternator test goes well tomorrow, what is left to check??

The my problem is new line, LOL.

12.1 volts is not an indication of a good, charged battery. Should be more like 12.7-12.9 volts fully charged as I recall.

Are you taking readings at the dash gauge (Notorious liars on jeeps), or using an multi meter at the battery?

multimeter across the battery for the 12.1. the 9v is a guesstimate from the dash, but it is apparent that there is a problem. even the turn signals were slow to flash while it was spitting and sputtering with dim headlights.

the 12.1 volts is also after driving it a few miles while it was having the trouble...

Well you may have more than one problem. Is the meter battery any good. As I said 12.1 volts is a discharged battery. Many of your other symptoms sound like a dying ignition switch, poor overheated contacts. The brown wire to the ignition switch and ignition switch are way undersized for the AC blower and the other stuff that runs off of it, like wipers, radio, turn signals, door locks, windows. The head light switches burn out too, and add to the overload of the ignition switch. Most of the running systems are powered through the ignition switch. The feed to alternator from the battery may go through the switch too.
PM 5-90 and ask him to drop by this thread. He is the alternator guru here.

The dash gauge is not linear, and not calibrated so what you think is 9 volts on the gauge is about 12. Mine runs from 12 volts to about 15 volts from the left side red area (where it ends) to the other warning area on the right side. The 8 volt and 18? volt marks on the dash gauge are a joke.

What does the multi meter read across the battery with the engine running?

And have you cleaned up the engine and firewall ground connections?

Ecomike said:

What does the multi meter read across the battery with the engine running?

And have you cleaned up the engine and firewall ground connections?

Click to expand...

the battery tells me 12.1 running or off. i have not cleaned that ground yet.

Upgraded cables are always a plus, and definitely cant hurt anything. Have you tried "jumping" your XJ with another vehicle and see if the issue wiht your problems is still there?

Johnnie Walker said:

Upgraded cables are always a plus, and definitely cant hurt anything. Have you tried "jumping" your XJ with another vehicle and see if the issue w

iht ​

your problems is still there?

Click to expand...

i threw the jump box on it and the stumbling cleared up a little, but i have not went from another car.

it started giving me trouble, so i came home and pulled the alternator. then i had them test it and got stumped there. i don't want to put it back on before having it tested somewhere that i can get actual data out of it. so i'm trying to figure out what else to test if the test goes well tomorrow...

OK clean the grounds next.

Search Google with key words ".org ignition switch" and do another for "headlight switch" instead of ignition switch. Google searches work better than ours in some cases. There are several good write ups here, some with pictures, on finding, pulling and replacing those 2 switches.

Just to cover everything check out the condition of the fuse box, under the dash way up under on the far left drivers side. Look mostly for loose fuses, bad fuse contacts, and of course bad fuses.

Have them run a full load test on the alternator!

Check the small starter relay near the battery. There are fuse links near it, and critical wiring and connections there. Look for overheated, burned or corroded wires and connections near that starter relay.

There are also some good threads here where 5-90 details how to test the leads to the alternator, engine off, power on, and engine running. Use "5-90" as the poster in the search, and use "alternator" as the search word in our search menu above, 6th from the left.

1) As mentioned, any suspect IP readings (particularly the voltmeter!) should be verified independently. Especially the voltmeter - it's a notorious liar.

2) Note the values charted below (I answer this often enough that I'll put a page up on it in the Tech section when I move the WiP site in the near future...)

3) When checking the alternator output voltage, there are three points that you want to check and compare: 1) The battery + post. 2) The starter motor relay screwpost. 3) The screwpost on the back of the alternator case. As you move away from the alternator, you should lose not more than .1VDC at each connexion (viz: 13.3VDC at the alternator post, 13.2 at the starter motor relay post, 13.1 at the battery post.)

4) Check and service all main ground connexions - you'd be surprised. In my experience (in the last thirty years or so,) probably 75-80% of automotive electrical problems could be tracked to shonky grounds. Also, make sure the terminals in the Weatherpack connector on the alternator (male and female) are clean and haven't gotten contaminated - these drive the voltage regulator, and can therefore cause you trouble (the Delco CS-130 is internally-regulated.) Also, get wiring diagrams and see where the regulator "sense" lead picks up its voltage signal - and make sure that connexion is A) getting full system voltage and B) is transferring that full voltage to the voltage regulator in the alternator (it may be a wiring fault that wants tracking down, and that can take a while. Wiring faults are so much fun to find and diagnose...)

5) If you take your alternator out to test it, do not take it to a "chain" store! Most of their test benches will only check voltage at ~.1-.5ADC, which isn't enough to run a decent flashlight. As current draw goes up, voltage goes down (this is how a "voltage regulator" drives current output on the alternator,) and if the alternator's current-generating capacity can't keep up for whatever reason, you'll show low voltage. Take it to an alternator/starter house - they usually have benches that can wring an alternator out properly (for instance, the shop I use for rewinds has a bench that Rod can use to tell me exactly the max current output of an alternator - not the rated output, but the max possible output. A useful little datum...)

Test-------------------Condition----Nominal-----Acceptable
Battery at rest.............KOEO..........12.6VDC......12.2-12.8VDC
Battery at idle/run........KOER...........13.6VDC......13.0-14.4VDC
Alternator Output.........KOER...........13.6VDC......13.0-14.4VDC
Cranking.....................START*........9.6VDC.......9.4VDC or better

* Crank your starter motor with the ignition disabled. Watch the DMM while a helper cranks for you. Do not crank for more than fifteen seconds at a test, rest for five minutes between tests to avoid overheating the starter motor. The voltage will drop sharply when you start cranking, you're looking for the value when it stabilises (after the "startup spike" of the starter motor. This is a known property of induction motors, and is perfectly normal.)

well, as usual i overlook the easy and go full bore into the major problems. At some point, probably when i replaced the battery, i pulled apart the previous owners patch job on the switched power wire to the alternator. once i put a jumper on those wires it charged just fine. go figure

tomorrow i'm going to pick up some wire and fix it right.

61scout80 said:

All of the battery cables show 0 ohms form terminal to their end point.

Click to expand...

That means nothing, here's why. You could take a hundred strand cable and cut 99 of the strands. You'd still have 0 ohm resistance though, same as on the intact cable. However, which one's going to be able to pass lots of current?

Voltage drop test is the way to go.