Alternator Not Charging Battery

[MaineMan87]

After two months of ownership and picking away at some punch list repairs, I was anxious to take my 74 AMC 304 CJ5 out this past weekend. I hopped in, turned the key, and nothing. It was clear that the battery was dead, but I didn't think of anything of it, since it had sat all winter before I bought it and another two months after I bought it. I put a charge on it and would try it the following day. It started up with no problems, for about 5 or 6 starts, but then the battery died again. The previous owner installed a new alternator before I bought it, but I was beginning to question if he hooked it up properly. I am not an expert mechanic, and electrical is probably my weakest link, but I quickly noticed that one of the wires coming off the plug of the alterrnator was cut and not hooked to anything. It looks to be a GM style alternator with an internal regulator. There is a 2-wire plug with a red wire and a black wire. The red wire is hooked into the positive lead on my battery, but the black wire goes nowhere. Where should this be connected? I picked up a new battery and solenoid, for peace of mind, but I'd like to get this alternator issue figured out before I throw the new battery in.

Also, while under the hood, I noticed that there is a purple wire that is also disconnected. According to the FSM, this should be hooked to the oil sending unit, is that correct?

Thank you,
Andrew

 

[Torxhead]

If your fsm does not have a wiring diagram in it, there are wiring diagrams available online or they can be found it aftermarket repair manuals.

 

[jdcaples]

Does this look similar to what you have?

View attachment 17564

-Jon

 

[Hedgehog]

Purple goes from the sending unit to the oil pressure gauge.

The Delco plug issue seems to be a fairly common problem. My Jeep came with a red (or was it black, can't remember) wire hooked to the line going to the battery and a white wire seemingly doing nothing but hang out in space. I asked almost the same question you have and got a steady stream of answers. Most all of them saying that there needed to be some sort of resistor in the line going to the run side of the ignition switch. The resistor could be a light bulb or a few inches of resistor wire. the resistance tells the regulator that there is a load and the alternator needs to start charging. From what I can gather this is mostly for low RPM operation, above a certain RPM the alternator will automaticly start charging. So, what did I do. I cheated is what I did. My alternator fried itself right infront of my little eyes, so I took it in and had it rebuilt with a single wire set-up. Quick simple fool proof. There is only one wire to hook up and thats the heavy with coming from the battery. This effects the way the alterantor starts charging. Start the engine, blip it up over 1100 RPM and you've got charging going on.

But, your wire hanging shouldn't stop your Jeep from charging, what does your volt meter say? It should be running at 14+ volts with a nice 12+ with the engine off.

 

[MaineMan87]

Does this look similar to what you have?

View attachment 17564

-Jon

Indeed. Thanks

 

[MaineMan87]

Purple goes from the sending unit to the oil pressure gauge.

The Delco plug issue seems to be a fairly common problem. My Jeep came with a red (or was it black, can't remember) wire hooked to the line going to the battery and a white wire seemingly doing nothing but hang out in space. I asked almost the same question you have and got a steady stream of answers. Most all of them saying that there needed to be some sort of resistor in the line going to the run side of the ignition switch. The resistor could be a light bulb or a few inches of resistor wire. the resistance tells the regulator that there is a load and the alternator needs to start charging. From what I can gather this is mostly for low RPM operation, above a certain RPM the alternator will automaticly start charging. So, what did I do. I cheated is what I did. My alternator fried itself right infront of my little eyes, so I took it in and had it rebuilt with a single wire set-up. Quick simple fool proof. There is only one wire to hook up and thats the heavy with coming from the battery. This effects the way the alterantor starts charging. Start the engine, blip it up over 1100 RPM and you've got charging going on.

But, your wire hanging shouldn't stop your Jeep from charging, what does your volt meter say? It should be running at 14+ volts with a nice 12+ with the engine off.

I will be checking the volts tonight, but I think you have lead me in the right direction. The alternator is brand new, so I will install a resistor on that wire and see if that fixes the charging issue at low rpm's.

 

[jdcaples]

In my CJ7 , I have the GM style alternator.

For what it's worth, my Painless Performance Chassis harness came with wires on the back of the fuse panel. It's wire 714. Wire number 714 goes from the fuse panel to terminal 1 on the alternator.

Here's the Painless diagram

View attachment 17565

Here's the fuse panel end of wire 714 (4th hole from the right, bottom row)

View attachment 17566

-Jon

 

[Hedgehog]

That is one of he best wiring diagrams I've seen in a long time.

 

[mtnwhlr]

A quick way to see if the batt is getting volts from the alt is to start it with a charged batt and pull the pos cable off the batt if it still runs the alt is putting out and is fine if it dies than it isn't.

 

[Hedgehog]

AutoZone and O'Rieleys will do a diagnostic check on your charging system for free. A new alternator does not = a working alternator.

Your Jeep should run for a while on a good recharged battery.

 

[jdcaples]

AutoZone and O'Rieleys will do a diagnostic check on your charging system for free. A new alternator does not = a working alternator.

Your Jeep should run for a while on a good recharged battery.

I took advantage of that service. My battery tested fine, but since it was 60% charged and not 100% charged, they couldn't test the charging system with their store gear.

The equipment was branded "Autozone" and it looked like an 18"x9" tablet computer with some electrical leads.

-Jon

 

[MaineMan87]

AutoZone and O'Rieleys will do a diagnostic check on your charging system for free. A new alternator does not = a working alternator.

Your Jeep should run for a while on a good recharged battery.

If all else fails, I will pull the alternator and have it tested. I'm just trying to get it hooked up properly, first.

I had a few minutes to look it over last night and have the following question. Does it matter if the "power" wire coming out of the plug goes straight to the battery or does it have to be connected to the post on the backside of the alternator and then have another wire go from the post to the battery? It's currently hooked up with the "power" wire going straight to the battery, but there is also another wire going from the post on the back of the alternator to the battery. I'm not sure if my CJ has the "dummy" charging light for the excite wire. If not, can I just put a 10-15 ohm resistor in line and wire it to the positive side of the resistor?

I really appreciate the help!

 

[MaineMan87]

One more thing. I traced back the purple wire that is disconnected under the hood and found that it's also disconnected behind the dash. Each end has a ring terminal. I've only taken the Jeep out for about 1 mile, but I believe the oil pressure gauge was working. The is a black wire connected from the oil gauge to a fitting near the oil filter, so I assume the PO replaced this at one time. The thing that confuses me is that the old purple wire has a ring terminal, but the wire that goes between the two now has some different ends on them.

Sorry to jump around, but the more I type, the more other questions pop into my head. My water temp gauge is not reading, and to me, this is more important than the speedometer, so I want to get it fixed. The blue wire w/tracer is connected to the gauge, but I quickly noticed that it was clipped under the hood when I followed it. It looks like the sensor is near the thermostat housing on the corner of the engine, so it should be an easy connection. Does this just need a simple ring terminal?

Thanks!

 

[Geep]

One more thing. I traced back the purple wire that is disconnected under the hood and found that it's also disconnected behind the dash. Each end has a ring terminal. I've only taken the Jeep out for about 1 mile, but I believe the oil pressure gauge was working. The is a black wire connected from the oil gauge to a fitting near the oil filter, so I assume the PO replaced this at one time. The thing that confuses me is that the old purple wire has a ring terminal, but the wire that goes between the two now has some different ends on them.

Sorry to jump around, but the more I type, the more other questions pop into my head. My water temp gauge is not reading, and to me, this is more important than the speedometer, so I want to get it fixed. The blue wire w/tracer is connected to the gauge, but I quickly noticed that it was clipped under the hood when I followed it. It looks like the sensor is near the thermostat housing on the corner of the engine, so it should be an easy connection. Does this just need a simple ring terminal?

Thanks!

If the blue wire w/tracer goes to the sending unit a ring terminal and a couple small nuts to attach to the sender post will work fine. You might just want to run a new wire from the back of the gauge sending connection to the temp sending unit.

 

[Hedgehog]

Warning - I can only speak about mine, but ...... The factory wire has a 90 degree bent socket that presses on the sending unit .... yes the sending unit is near the thermostate ..... My wire was toasted with the coating breaking off from normal engine heat cycles, so I thought I'd replace it with a nice fresh wire with a ring. Problems hit when I tried to fing a nut that fit the threads on the sensor. I tried everything, nothing worked. Finally I pulled the sensor and found much to my surprise that the thread wasn't a thread at all, it was backwards and too steep. Best guess a gripping surface for the factory terminal boot. What should have been a 5 minute job turned into a frustrating 2 day job. ..... oh yeah, you can't just pull the sensor, it's in a water jacket that is lower than the radiator, so the radator needs to be drawn down about 1/2 before pulling the sensor.

 

[Geep]

I replaced my temp gauge with a Equus gauge that came with a matching sensor,a threaded post,two nuts ,washers and a ring connector. The original was a 90 degree fitting that pressed onto the sender post as you said Hedgehog and it too was brittle and the wire was toast. I removed the oriiginal sensor when the engine was cold and only a very small amount of coolant came out, probably about a shot glass full.I dont know if that is right but everything seems to be working fine now ???

 

[Hedgehog]

A bunch of fluid came out of mine, I mean a bunch before I reset the sensor.

Edit: But I forget that my jeep was sitting in my driveway on a slope.

 

[MaineMan87]

Thanks to you guys, I feel comfortable with what needs to be done to get my temp gauge back up and functioning. I also feel comfortable with the rewiring of the "hot" wire from my alternator. I thought I felt comfortable with the rewiring of the "excite" wire and spent my lunch break trying to track down a 10-15 ohm resistor that I could put inline between the alternator and the coil, but easier said than done. I was able to find a 5 ohm, but I'm not sure if that would do the trick.

Do I still need an inline resistor, even if my ignition coil has an internal resistor? Is there any chance that my CJ would shut off with the ignition (as it should) if I DON'T include a resistor? I'm tempted to try it without one, and if my Jeep stays running, I know what my issue is and i could easily a resistor.


Here are some recent pics of my rig.

Thanks again,
Andrew

 

[Aaron]

I recently went through this with my jeep. I have a 75 CJ5 with a new painless wiring harness. I have a Delco Remy alternator that is just like the one that Mr Jdcaples provided a picture of. I didn't have to put a resistor on anything and it would charge just fine. I did have to put a diode on the exciter wire as it would backfeed the ignition coil and not shut off.

 

[MaineMan87]

I recently went through this with my jeep. I have a 75 CJ5 with a new painless wiring harness. I have a Delco Remy alternator that is just like the one that Mr Jdcaples provided a picture of. I didn't have to put a resistor on anything and it would charge just fine. I did have to put a diode on the exciter wire as it would backfeed the ignition coil and not shut off.

Where did you get the diode? I've read that 276-1143 and 276-1144 from Radio Shack both work.