Help! Alternator? Battery? What's going on? 1990 240 DL
 

Oops, I realized I should have posted my question below instead of in the General category. Maybe someone in this section can help me with some trouble shooting? I've done some more reading in regards to what I've written below and I wonder if anyone can answer this as well-

Does a 1990 240 DL wagon have an external voltage regulator- or is it in the alternator?


Ok- here's what's happened so far....

Car was dead the other day. I had a friend jump it (took a long time), drove it home the long way to re-charge the battery.
Got home and turned it off. Turned the key back on and it was dead.

Next day-
took the battery off, tested it, and it was low, but not dead.
took the alternator off (they said it was dead), got another one, put it on, and tried to start. Needed to jump it, and as soon as I disconnected the jumper cables the car would die. Thought I got a bad alternator, so I took that one off and got another. (they didn't test this one that I brought back though)

Put the 2nd alternator on and couldn't even jump the car until I ran the car jumping it for 1/2 hr.
Finally started the car, ran it for 1/2 hr-45 min.
Turned the car off, and back on again. Nothing.

Now, here's the weird part.

When I was trying to jump the car the last time (before running the other car for 1/2 hr with cables connected) I tried a couple of times to start the car and what happened was bizarre.

The speedometer jumped around and read 60mph and then my odometer started turning like I was driving!
What the *@*!!@*
Turned the ignition off and tried again, all dash lights were lit up (as before) and the same thing happened! I was stumped!

I let the jumping car run for a while longer to see if I could actually start it and after that 1/2 hr, I was able to start the car. (but it didn't start again after turning it off as I said above.)
No more speedometer and odometer weirdness.

Now- where do I start? What do I look for? A short? Something isn't allowing my battery to stay charged even though I ran it for quite some time.
I'm completely befuddled. Can you help?

RE: Help! Alternator? Battery? What's going on? 1990 240 DL
 

A $10 multimeter would help a lot, read the battery when its not running then read it when the engine is running.
Read the volts at the alternator too.
Then you know what is doing what and where to start looking if its losing volts somewhere in between.

I get 12v engine off.
14v engine running and 14v at the alternator.

The V regulator is obvious if its mounted externally on youralternator, looks like this
http://www.fcpgroton.com/images/3523710.jpg
2 screws and its off.

But seeing as you're on #3 alternator it is probably wiring, specially as the electricals are jumping around like theres a harness break. Some of the wiring passes under the engine and it could be there, start with a voltmeter though.

Hi. So I know this is an old post, but did you ever figure out the issue? I'm having what seems to be the same problem... I haven't replaced the alternator but I'm getting a good 14 V when running... seems like something randomly shorts out and kills the battery, and right before that happens the speedometer jumps around wildly. Any help would be greatly appreciated!

what do you mean by 'kills the battery' ?

a direct short across a lead acid car battery can generate enough current to arc weld. most circuits connected to the battery are fused such that if the circuit downstream of the fuse shorts to ground, the fuse blows, protecting the wiring from meltdown.

what you describe sounds more like a flakey ground to me, than a short.