Hello all,

I'm having alternator problems. Just replaced my original sticky 17ACR with a new one which I'm told was producing 13.2v when removed. With my engine running at about 1000rpm I get 19-20v output (the two output terminals combined)! This is under no load as it's not connected to the battery (because I don't want to fry everything), but it seems a lot to me. Can anyone confirm, or is this OK for no load? I can replace the regulator but as it worked well previously I wonder if there's something else going on.

It seems the same whether I excite it through the ignition light circuit or if I take a wire directly from the battery +ve terminal. Maybe I 'll try exciting it from the battery with a charger on it next, so it gets 14v or so.

Any thoughts welciome - particularly on whether the 19v is normal or a concern.
Cheers,
Stu

I think you should test it with a small load, say a 21w indicator bulb

That sounds like a great idea. Just tried and I get the same voltage... but the bulb didn't light up.

you should not run an alternator without a battery in the circuit cos it will fry it, also it needs to sense the battery voltage or it wont know how much to charge

I had a quick look at some old workshop manuals I have, and found the test procedure for the acr15, so a bit more digging acr17 is very similar, and pages 449 and 450** of the TR6 workshop manual shows the test procedure for both acr15 and 17,
http://www.tr6pi.com/TR6%20workshop%20Manual.pdf
edit
**sheets 1&2 of section 86.10.01
edit 2
the pages that precede and follow also have the internal circuit diagram and overhaul instructions for the alternators.


[Edited on 19/7/22 by gremlin1234]

Ah right, thanks, hadn't realised I shouldn't run it without a battery - thought I was doing the right thing to avoid frying other electricals if it is overcharging! I'll put the battery back in the circuit and just disconnect the other stuff I'm worried about.

Thanks very much for digging those out Gremlin, super useful! I had a look through my Mk2 Escort Haynes but it didn't go into enough depth, the TR6 one is great. I'll check if I have a variable resistor the correct size and if not order one to have a go at the weekend.

Thanks and another thing learned!

another detailed manual
http://lotus-europa.com/manuals/misc/electrical/17acr.pdf

Fantastic thanks again Gremlin. No time last night or tonight but I'll get back in there on Friday and over the weekend!
Thanks

Thanks again - test procedure passed so wired back up and and now producing 14V with no lights etc on, which seems correct.
IVA retest next week!

excellent, hope it all goes well