Ford Charge System at Idle

[Cartierusm]

I've got a Blue Bird 2002 Ford E450 with the heavy duty alternator. I'm trying to figure out if I have a charging system problem.

Does the bus charge while at idle and if so can it run everything needed? Where I live I'm in traffic a lot, which means I'm running A/C while in traffic and the A/C in this bus is on the side so it's running 3 large electrical fans.

I did that one day and the next day it didn't start without a jump from another running diesel.

[cadillackid]

its possible for an alternator to go partially bad... meaning the diode bridges can partially go bad and the alternator wont put out what its rated at... esp at idle...

when I added A/C to my DEV bus.. (2 A/C indoor coils and a big 3 fan outdoor unit)... I installed a Bosch "school bus" alternator thats designed to put out 80% of its power at 1200 Alternator RPM (which is about 600 engine RPM).. its a 200 amp unit.. the old one still seemed to work, however when i had it tested it was only giving me 60% of its rated output.. so on a normal day with just a couple fans on or such it appeared to work great.. you may want to get your alternator tested to make sure it can put out its rated output.. and also look up the SPECs on it to see what its amp output is rated at against RPM.. remember RPM rated will be alternator spindle RPM not engine... most alternators spin at twice the speed of the engine..

-Christopher

[Rameses]

It's also possible for an alternator with a bad diode to draw amperage while the engine's off. The bad alternator itself can drain the batteries.

[Cartierusm]

Ah will do. Thanks. I believe I read that this was a heavy duty alternator and put out 160 amps, but when I looked under the hood it has a sticker on it 'remanufactured' so it might not even be the right one.

Thanks.

[Cartierusm]

Just checked the voltage when the bus is off, it's around 12.7 VDC and with engine running it's 12.8 VDC. So something is bad. Does with test categorically mean it's a bad alternator? I guess one of the auto parts stores can test it if it's off the vehicle.

[Rameses]

It's not 100% guaranteed that it's a bad alternator, but it's a safe assumption. It's possible, though highly unlikely, it could be a bad connection someplace.

Just go ahead and pull the alternator and take it to a parts store. Like you said, you can get it tested there and know for sure.

[Cartierusm]

Thanks Rameses. Turns out this alternator has the plug in voltage regulator in back. So I'll test that next.

[AlleyCat67]

Sounds like the regulator is removable, correct me if I'm wrong....

If that is the case, and that's the problem, then it could be a cheap fix.

[Cartierusm]

Yes Napa told me it has the removable VR, cheap I don't care about I care about if it's easier to remove than the alternator as it's located in a size 2 child's shoe box of an engine compartment. VR is $90, new alternator with VR is $140 for the 130 Amp model, which is what should be in there.

[AlleyCat67]

A little more expensive than I thought it would be but still cheaper than a new alternator.

I hear you, those van type front ends are like working on an engine in a broom closet.

I wish you luck with getting the issue resolved, hope you get it quick.

[cadillackid]

some people like external regulators as it used to be the alternator rarely ever went bad but the diodes in the regulator are what often went bad so the external regulators were chosen and could be repaired fairly easily..

the newer alternators tend to be somewhat more reliable.. however other than bearing failure its often something in the regulator portion of an integrated alternator that dies... that said the newer ones can and do last many years. esp if your bus isnt on the road all the time. (just a camper or a few k per year)..

-Christopher