P38A P38 battery / Altenator oddness

hi all,

I've been having some intermittent odd issues with my p38 (odd eas and clicking relays), which seem to be electrical. This culminated in her loosing all dash output, pulling away oddly and eventually stopping at a junction and refusing to restart. Unfortunately the missus was driving, which didn't go well, thankfully all was ok and the rac diagnosed a bad Altenator.

I'm currently on holiday and about to order some parts for my return, but wanted to canvass for opinion. I've read a few posts on some forums that the symptoms she experienced ( pulling away in wrong gear, loss of rev counter and speedo and traction failure message) are typically Altenator related, but I've not had an Altenator fault message. We've had a flickering battery light on a couple of occasions, but no dash message.

I've tested the Altenator output from the back and it's reading 14v. After sitting for a week the battery is at around 11.5v, so I suspect that definitely needs replacing, but after a run its sat around 13.8. The rac chap hooked up his tester to the battery and read the battery at 11.8v with engine running hence the blaming of the Altenator. He didn't check it At the back. As we were in the middle of a busy junction, I just wanted to get the vehicle moved (I'd arrived at this point).

He hooked up a temp battery pack and I drove home with no issues. Upon arrival I noticed the engine was idling around 1500rpm, which was odd. When he disconnected the battery pack I received all the usual Gearbox Fault messages I'd associate with a bad battery.

I'm happy to replace the Altenator (planning to do this myself), but thought I'd get some opinions before I send out on an alt and battery.

Cheers

Steve

A bit more info on engine and year will help, ideally you want 14.5v at 2000rpm with all the lights and everything you can put on, if you get a new battery get the biggest you can fit ie 110-120 ah.

brianp38dse said:

A bit more info on engine and year will help, ideally you want 14.5v at 2000rpm with all the lights and everything you can put on, if you get a new battery get the biggest you can fit ie 110-120 ah.

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If it's 4.6 with a 150 amp alternator that is.

Oh well i was wrong, well it gave the thread a bump.

Can you take the battery off, charge it and then see how long it holds a charge. 14V exactly? Too high for the lower output alternator and too low for the higher one so does sound odd. Too low for a calcium battery that's for sure.

Thanks for the replies. Apologies for missing the salient point of what model it was, I was using my phone of a crap wifi connection! She's a 4.6 Thor engine with an lpg conversion. So I'd guess it's the 150amp.

Would an alternator fault warning be expected all the time? Or just under certain circumstances.

stevej69 said:

Thanks for the replies. Apologies for missing the salient point of what model it was, I was using my phone of a crap wifi connection! She's a 4.6 Thor engine with an lpg conversion. So I'd guess it's the 150amp.

Would an alternator fault warning be expected all the time? Or just under certain circumstances.

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Other people have had issues with no warning so it is possible.