My son has a 2000 Neon with him at college. He left his lights on and the University's Safety Services came to give him a jump. The guy that hooked up the jumper cables had them reversed at first and my son said it arched a bunch (obviously) and then some smoke came from around the starter. when the guy switched the cables and hooked it up right it started then when they pulled off the cables off it died.

The battery was 3 years old so I changed it. Started up and the load tester said 12+ volts and that it wasn't charging.

Looked for the area of the reported smoke and found the fusible link burnt that connects the alternator output to the post on the starter. Changed it still no charging. I used 12 awg wire with a 30 amp inline fuse since Auto Zone didn't have a actual fusible link and I didn't want to hook up the straight 12 awg wire with no protection.

Pulled the alternator and took it to Auto Zone and they tested it and it failed right away. replaced it.

It started right up and the load tester said it still wasn't charging. Checked the fuse and it was blown. I used my Fluke multi-meter and it said the alternator was putting out about 31 volts at idle and up to 90 volts while revving the motor on the feed side of the fuse connector with the fuse removed.

I'm suspecting the PMC since the alternator output voltage is regulated by adjusting the field winding voltage to the alternator if I understand that right.

My question is with the alternator output wire disconnected from the battery should my voltage be somewhere 14.5 -13.8 volts steady while the engine is running or does the PCM sense the battery voltage is low (12 volts) and really try to crank out the voltage to put a fast charge on the battery?

The college is 3 hrs away and Im working on this thing in the dorm parking lot. So i'm limited to what parts I can get and tests that I can do on location

 

31-90 volts would be a bad alt too, better have az re-test the new one before they stick you with it, the voltage regulator senses the voltage but it should not be that high unless your flukes on the wrong setting Does the car die ones you have it running an pull off the positive cable? If so your alt's no good....


someone might wanna chime in I had a lotta tx 6% beers last night

make sure your ground cable is good and making 100% contact

 

No my fluke was on the right setting VDC. I talked to a guy at our Dodge dealer and says the PCM looks at the voltage at the battery so it may be spiking up since its not connected.
Has anybody had luck putting an external voltage regulator on one of these? I seen where they have done it on the Dodge Rams but haven't seen it on a Neon.
I have checked the ground at the battery and it looks good and tight. I haven't checked to see if there is others that I may have missed.
Last weekend was when I was working on it and it was 22 degrees and snowing in a a parking lot at a dorm. I may not have been too thorough

 

I run 220amp alts on my boats, and rebuild then when they get irregular but never seen/had a small alt crank out that kind voltage in my 25 years of wrenching un-professionally. Have you had a chance to take the alt back anywhere for a re-test? I'm stumped on this other wise, that mess in the 22 degrees ain't fun either

 

No I haven't had a chance to take it off yet. Unfortunately I had to leave the car sit in the dorm parking lot all week. I'm in southern Ohio and he is in northern Ohio so it's like a 3 hr drive to get there. I'm trying to regroup before I head back up this weekend. The voltage went up proportionality with the RPM there was just no voltage regulation. Everything works fine when its started. I have the output from the alternator off due to the high voltage I'm little leery of hooking it up until I get a confirmation on the output voltage when that output wire is unhooked.
I have a 98 Neon sitting in my driveway. I'm going to start it with the output lead of the alternator unhooked and see what voltage I get. If I get 14.5 or around there I'm going to call the PCM bad.

I'm the lead maintenance technician for the robots at Kenworth Truck Co. so I'm familiar with DC volts and weird electrical problems.... but this has me a little puzzled.

 

I tested mine at lunch with the + wire off, 14.1-3 (I'll try at the alt post after work)

lol My mexico made duralast must be going sooner then I assumed or it's needing a bearing kit like most bosch alts do after 100k

 

I check my 98 neon and it put out 14.4 volts while hooked to the battery and 15.8 with the positive unhooked while running. I assume si.ce its not sensing battery voltage. I tried hooking up an external voltage regulator but it still cranked out a bunch of voltage. I'm going up this week and renting a uhaul Dolly and dragging it home so I can at least have it in the garage. I am thinking it may be something with the alternator now since the external regulator didn't help.

 

Ouch! If you can swap the alt or have it tested it sure would be Uhaul's rip off fee's.... I had to do that a few summers back and I wish I'd have worked on it in the ditch instead of towing it home with my 9-12mpg 03 ram lol

Either way let me know so I can add this to my neon log of PDF notes =)

 

Ok I got the thing home and pulled the alternator off and took it to AZ and they tested it OK. I watched them and watched the screen and everything looked good. I took it home and reinstalled it on the Neon. I tried hooking up an external voltage regulator and (85 dodge pickup) started the car same thing high output voltage. I wired it up based on the attached drawing. only thing is I completely removed the plug going to the field windings. I didn't think that should matter.

 

Man I feel like retard, never had one go that high off the chart. Even the added regulator it should have cut some output down I would assume. All the ground wires good an clean making contact? Not just the one on the battery, there's 2 more, 1 off the upper torque strut & on mine from the bell housing near the starter for example to look for.