Hello everybody! I hope your holiday season is going well! Before I go into my issue, I just want to express my appreciation for the time and trouble that many of you give to help each other out. Without you, owning and maintaining these old rigs would be difficult, or in some cases impossible. Thank you!

About 4 years ago my '93 E-350 (former ambulance) with 7.3 was having no electrical issues, and suddenly stopped charging my batteries. I won't through the usual suspects, checked the battery connections, cleaned the ground connections. No charge. I assumed it was the alternator, so I replaced it. Problem solved... So I thought. After 2 days of normal operation, once again stopped charging. But I had to go to work, so I charged the batteries and drive to work. On the way to work, it started charging again. But once the engine was fully warmed up, it stopped. After work, I started the engine, and it was charging normal. 10 minutes down the road it stopped charging. Sometimes I'll be at idle, it won't be charging, I'll blip the throttle and it will resume charging. But then stop after a few minutes. I've replaced every battery cable, and made sure they were tight clean connections. I've had the alternator tested (165amp leece Neville), and it's fine. Any ideas? It acts like something is loose, or making intermittent contact, but I don't know where else to look. The lead wires coming off the alternator are tight/clean as well.

By the way, I replaced the alternator again, and it's still happening. It's internally regulated as well. Is it possible that an external regulator is fighting with the alternator's internal regulator? I'm pretty sure the original was internally regulated.

Please help. Thank you!

 

That definitely does sound like something loose, or not making contact properly. Being an ex-ambo, is it possible whoever took off the ambulance body did a sloppy job disconnecting everything? Nothing crazy like a slipping belt on the alt pulley? I’m sorry I’m not more help cetane, this will get bumped to the top and somebody with more experience will hopefully chime in.

 

Thanks for the reply! It still has the Ambulance box, but the wiring was definitely disturbed when the federal bar, siren, and comm systems were removed. For the most part the box (called the module) wiring is separate from all running systems for driving. There are some exceptions, such as a circuit that increases the idle speed when parked in patient mode, to ensure sufficient power to the equipment, and headlight/lighting flashing circuits. There's a circuit board in the module that controls these things, but not the charging of the batteries. But certainly through it's many miles and heat cycles, and hands in the wiring, there's bound to be a short or open circuit somewhere.