Club 80-90 Forums

Using a multimeter on volts only.

I'm trying to check if my alternator is OK, I'm getting 13.4volts with the ignition on and the meter across the battery, when I run the engine it reads 14.80 volts..is this OK ?

Would this indicate that the alternator is supplying sufficient power OK?

The reason I ask, is when I'm running the engine with the headlights on and the battery is fully charged, the panel lights don't seem to brighten up (as when the alternator kicks in), they seem to flicker ever so slightly.

Have checked the alternator section in the wiki but as you can probably gather I'm hopeless when it comes to alternators

Thank you for any info/help.

I'm not Mocki... but that's one healthy alternator you have

the dash lights may be a fault with the actual dimmer control

kevtherev wrote:I'm not Mocki... but that's one healthy alternator you have

the dash lights may be a fault with the actual dimmer control

Thanks Kev the Rev, I tried the dash lights control in various dim/bright positions.

I've got one of those chargers that you leave on during lay-ups, so I know the battery is fully charged.
I've tried the indicators when the H/lights are on and the dash lights flick slightly, in time with the flashers, and flick when you try main beam and dip on the headlights.

All this slight flicking whilst the engine is running or not.

It is pretty unusual for a batteries standing voltage to be quite that high, normally I would expect something in the region of 12.6-12.8volts max
Unless of couse you have one of the newer Silver Type batteries that I believe have a slightly higher nominal voltage (not sure what that is)
Bosch used to quote range of between 13.8 and 14.2 volts output on the alternator (started and reving say 2,000rpm)
All your figures look slightly on the high side to be honest, is your meter accurate?
Martin

I'd agree with Red Westie for voltage range of a fully charged lead acid without the engine running, that sounds a bit high. I once found my multimeter to give silly high readings when its internal battery was nearly flat (not helped by the fact it doesn't auto off so I keep running it flat). New batt inside and it seems far more realistic - might be worth compairing with another or changing batt if its known to be old (or in my case drained ).

if you have been testing it just after switching off your chrager, the standing voltage sounds a bout right, and your alternator isnt really having anything to do........ measure it when the battery hasnt been on charge for two or three days, and it will be more like the above reports.

I dont think you have a charging problem, but you may have a bit of a earth issue at the dash end by the sounds of it, and like Kev says, the dimmer on the headlight switch will be lowering the brightness a bit even on max, its a wirewound resistor, with a wiper, which when its as old as it is, isnt surprising its dropping a bit, the wire will be "dirty" where the wiper travels.......

Had a similar problem with my dash lights had to hold the dimmer control to get them to come on. I sprayed the dimmer contol with switch cleaner obviously some went behind and onto the resistor and all is now well. Switch cleaner available at Maplins
Good luck

Thanks guys, will leave it a few days off charge and see what happens.

In the mean time I'll check/clean the earth connections, and have a go at the dimmer switch.

Tex Ritter

Right, have been looking at the battery again after 4 days elapsed, without being run/charged.

Standing: 12.77 volts
Tick over: 14.17 volts (approx750rpm)
1500 rpm approx: 14.18 volts.

Haven't done the earth problem yet, but what do you think about the readings?

Thanks for any replies or advice.

sounds bob on that buddy !!

yep... perfect

indeed, that battery is as healthy as a healthy thiing going on those readings..........

That's more like it.....spot on.
Martin

Thanks guys for your inputs, feel a lot more confident now.