It's a 2000 Grand Caravan 3.3L, high mileage.
The charging system seems to be failing intermittently but increasingly. Things will be fine for several days then I'll get a battery light (low voltage) and then the car will die as the voltage continues to drop.
Replaced battery and checked the entire charging system (passed all tests with alternator putting out good voltage and amps) but ran into the same problem a week later when the new one discharged.
During one of the "events", I measured 11.5V and dropping running at
2K RPM (and only slightly less turned off); took this to be an indication of a bad alternator. Yesterday I took the alternator out (and what a job that is) and brought it to the parts store, where it passed their test with flying colors. Put that alternator back in, cleaned and tightened all battery connections etc. and immediately got 14V into the battery. Hooray.Of course this morning I am back to the battery light being on and no apparent charging all day (less than 10V upon returning home).
So, after a bit more research, I am left with these possible theories:
- Bad body control module -- the voltage regulator is apparently integrated into this computer (!) and if it is bad it could be preventing the charge from reaching the battery.
- From a glance at the Haynes book at the store there appears to be an "MDS relay" (I may be misremembering the name here) between the alternator and the battery; no relay by this name appears to be in the main relay center next to the battery and the relays under the dash are unlabeled. If anybody can tell me where to find this relay I can have it checked.
- Grounding problem, probably to the computer module. The ground connection to the battery is good; not sure how to proceed with checking this.
- Truly bad / intermittent alternator -- I've never heard of one go intermittent in this way; a replacement is a nonrefundable 0 and I hate to shotgun without knowing.
- Bad (brand new) battery -- don't think this can be it, since it takes and holds a charge from a battery charger, and runs the car for a reasonable amount of time before dying.
Any other ideas, or ways to narrow this down. I am tearing my hair out here and the cost of sending an electrical gremlin to the shop is scary.
Thanks
JGM