Alternator issues (I think...)

Apologies to all if this is covered elsewhere. I've searched hi and lo. Coolant and radiator problems are resolved and Tonk is now running beautifully, when I can get her to start, all jump starts. I replaced the battery with a new one, as I said elsewhere. but it's not charging, or at least I don't think it is. My question is what voltage should I be getting at the battery posts when the engine is running. I've got a Lucas 16ACR (again, I think, all the markings/identifiers are obscured/obliterated). I'm currently getting 12.8v with the engine running and 11.93v with the engine switched off. I've tested for volts leaking and I'm not drawing any current when everything is switched off.

Grateful for any help.

Thanks,
spins

That's way too low. Circa 14 volts whilst running.

Flossie said:

That's way too low. Circa 14 volts whilst running.

Click to expand...

My thoughts too, thank you for confirming.

spisn

Check voltage at the alternator as well, you may have bad wiring or dirty connections. Pull the plug out the back, if it's got one and clean the ends up. The brass connectors can go green and manky.

Those little 18 ACR's do not put much out but do as Flossy says and make sure belt tension is correct. I have one as a spare for when other alternators pack up,got me out of trouble several times [ and a couple of mates]

The large Lucar connectors on the alternator electrical plug can make a bad contact. These are live all the time, so, if you're going to poke about in that connector, it's best to disconnect the battery first.

Does the charge warning lamp work correctly?, i.e., does it come on with the ignition, and go off as the engine starts?

Thanks @Flossie and @Tall Ratbag for your advice.

The charge light does go out within a couple of seconds, once she's running from a jump start.

Your advice raise a couple of questions:
1 Forgive my ignorance but how do I measure voltage at the alternator, not a lot of room to be poking probes and where do I poke them?
2 If the 16 ACR is a bit 'inadequate', what would you recommend as a replacement? Please bear in mind the battery is a new Varta 12v 60aH. I also have a 12v 80aH in a shed that came out of Tonk initially, looks reasonably new and in reasonable condition, but I replaced it without thinking too hard: not convinced it's banjaxed.

Thanks all,
spins

If you do not do much night time driving or have power hungry extras then its fine,An over night charge with a trickle charger now and then will keep battery in good order.

Have you got the plastic plug on the back of the alty, 3 wires (iirc) coming out of it?
Might have a clip holding it on?
Remove that plug and check for cleanliness on both the plug female terminals and the male alty terminals..
I'm unsure what terminal does what on them, one (thinner wire) will be to the dash warning light and the other one will go to the battery to charge it, the 3rd one? Dunno sorry.
When you find out which terminal does the charging stick the probe on it, engine running, other probe to a good earth (battery earth) and see what you get. If it's good there then it's the plug/wiring. If it's bad there then the alty needs replacing/repair.

>>1 Forgive my ignorance but how do I measure voltage at the alternator, not a lot of room to be poking probes and where do I poke them?

The wiring connector comes apart, you can take the back cover off it, and reach the terminals there. You'll find 2 big terminals [brown wires], and a smaller terminal [brown / yellow]. The small terminal is for the warning lamp, which sounds like it's working correctly, and the two larger ones are the alternator's output. With the engine running briskly [output is very low at tickover, so, get it revving at 2000 rpm or so], if the alternator is charging, expect something more like 14V there rather than 12V.

If you find 14V at the alternator, and only 12V at the battery, then, you need to check the wiring between the alternator and the starter solenoid.

>>2 If the 16 ACR is a bit 'inadequate', what would you recommend as a replacement? Please bear in mind the battery is a new Varta 12v 60aH. I also have a 12v 80aH in a shed that came out of Tonk initially, looks reasonably new and in reasonable condition, but I replaced it without thinking too hard: not convinced it's banjaxed.

The standard alternators are absolutely fine unless you've added lots of extra consumers.

The advice to check the fan belt tension is very excellent.

just measure the battery, a\with engine oiff battery should read 12v if alt is charging this will rise to 13v with engine running

I had a similar problem with Henry and just ordered a replacement from eBay. I went for the 50amp flavour for about £50.
I have put lots of electronical stuff in him with no problems what so ever including a split charging system and it runs everything without issue. Constant 14.4 volts from start up.

Oh, and it has the extra (W) terminal for my genuine 1965 series Land Rover Rev counter.

Made from the internals off a marine diesel tachometer spliced into a series 1 speedo.

Thank you all again. I must be losiong my touch, I hadn't considered revving the engine while measuring voltage at battery posts. The 12.8v is at idle. I'll report back. Watch this space...
spins

Still only 12.8v at post. Shows 14.01v when I check while still connected to the slave battery on Mondeo with Mondeo engine also running. If I disconnect the Mondeo, it drops back to 12.8v, so the more I look the more likely it's the alternator. Sorry, should have added that the fan belt tension is fine: about 1/2in play at the center between water pump pulley and alternator pulley.
spins

sounds like alternator

Check the brushes and slip rings but sounds like some of diodes gone causing loss of capacity and voltage Westronics https://www.youtube.com/user/WestronicsIrl/videos

make some brilliant test videos on all makes of Alternators and starters You should have about 14.4 volts with engine running at idle.

On another note i run my series 3 2.25 petrol on one of these 75 amps since 2014 from The starter motor company although plenty on ebay like this Note it is a right hand version you need https://www.ebay.co.uk/itm/NEW-LUCA...182726318003?_trksid=p2349526.m4383.l4275.c10

I also uprated the cables from the battery There is a stud so you can run a made up cable with ring terminal straight from alternator to the battery positive point, usually by the solenoid, on another note all my cables are in protective plastic copex armour through the gap in the block to avoid chafing shorts

You haven't said if you've checked/cleaned the alty connectors yet, and tested output AT the alternator as well as the battery.
A new alternator will give the same poor readings if the plug is w@nkered.

Sorry @Flossie, connectors cleaned and crud removed from cabling and still outputting 12.8v checked at the alternator. While doing that found a cable, green, waving in the air and a spade connector hanging in the air. spliced them together and lo, the oil warning light comes on and stays on permanently. Don't thinki it's oil pressure, as it was doing that all the way down the road when it was running, suspect oil pump or blocked filter in the sump. Gosh, this is fun!
spins

In splice the green cable. Then Put the green cable onto your oil pressure switch. Bet it goes out?