Alternator output a bit low?

[Chris]

Checked my alternator this morning and it's only just kicking out 12v. I know that output goes up and down according to demand or something like that, but isn't output usually around 14.4v? Batteries are good and less than a year old, but they seem to be a bit low on standing voltage. Probably because they aren't getting a good blast.

I am facing immanent failure or something?

Chris

 

[BobMurphy]

Chris,

It will depend on the point in the cycle at which you tested it.

I had an Ammeter on my old LandRover. On initial start-up the charge was around 35 to 50 Amps (high Voltage) but after a couple of minutes it dropped to a trickle charge (lower Voltage).

If your batteries are good and you are not applying any load (lights, etc) then the Alternator Voltage will be down to just above battery voltage once everything has warmed up and settled down.

If its only showing 12 Volts on initial start-up then you might have a problem.

I have had to replace the brushes and internal control box on Lucas Alternators, not sure about Nippon-Denso though (if that's what they are).

Bob.

 

[Ecoman]

12V is way too low. The alternator, even on tickover, should kick out just over 13V. A good, healthy battery should sit at around 12.9V at rest so anything lower than that coming from the alternator and it will still be draining the battery.

 

[Chris]

That's what I was thinking. I have a local place that tests and re builds. I may whip it off and take it in for a look see. Don't fully understand alternators, but I thought that they either worked or they didn't. What would cause low out put? Don't get me wrong, everything is working perfectly, starts first time after standing cold for a week, lights are fine etc etc, just that out put is very low.

Chris

 

[Graham]

12V is way too low. The alternator, even on tickover, should kick out just over 13V. A good, healthy battery should sit at around 12.9V at rest so anything lower than that coming from the alternator and it will still be draining the battery.

.
Eco is right, sorry Chris, looks like some thing is amiss.

perhaps one of the diodes in teh rectifier pack.

There are generally 9 diodes in a rectifier pack.

3 small ones for voltage (wich determines amps output)

and 6 big omes fro rectifying the 3 phase AC output, (3 forwat diodes, and re reverse diodes.

Maybe 1 just gone?

Gra.

 

[Scott]

Chris - As the other posts have said, your reading does sound too low. You should be seeing something in the 13-14.5V region.

Another test that helps give an indication of how an alternator is performing is to start the truck up and measure the alternators output, then switch on all your electrical loads headlights, heated seats & read window etc. Now go back and see what the alternator is putting out, it should ramp up output to keep up with the load. If it hasn't then you know it's only going to be a short time before it lets you down.

 

[Chris]

Thanks Scott. I thought of that. Just not been outside again. But I shall make a cuppa and give it a go.

Chris

 

[Chris]

Definitely low. Everything on, alternator not making 12v.

Time for a rebuild perhaps. This might be worth a punt http://www.ebay.co.uk/itm/DENSO-126000- ... 0573152752

Chris

 

[MuckyPup]

Anything less than 13.9v and you're not charging
(12.7v NBV plus 1.2v differential to actually charge = 13.9v)
You should hopefully never drop below this except during cranking, but you might if "everything" is switched on.

 

[Ecoman]

I bought a 120 Amp one from The starter motor and alternator company. Not a bad price IIRC and it works a treat

http://www.startermotor-alternator.co.uk/



Just dug out the invoice and it was £135 delivered

 

[Chas]

I bought a 120 Amp one from The starter motor and alternator company. Not a bad price IIRC and it works a treat
http://www.startermotor-alternator.co.uk/
Just dug out the invoice and it was £135 delivered

When did you buy yours? I bought two, one as a spare, I paid £120 each, also got a starter motor from them for £150, also a spare, that was August 2011

 

[Gary Stockton]

Would a 120 series alternator fit? That's a 120amp output and there are a few on fleabay.

Cheers

 

[Chas]

Would a 120 series alternator fit? That's a 120amp output and there are a few on fleabay.
Cheers

It fitted with a slight bit of fettling, each end of the pivot point needed little filing to fit between where the pivot bolt passed through, but that was the only problem.

 

[Ecoman]

When did you buy yours? I bought two, one as a spare, I paid £120 each, also got a starter motor from them for £150, also a spare, that was August 2011

July 2011 so you got a cheap deal. Saying that I was probably humped for postage because obviously living north of Aberdeen its a seperate continent

I saw a couple on Fleabay but to be honest I didn't want to chance a product of that value to a random seller.

 

[Chris]

I've ordered that voltage reg from California. Shouldn't take too long and the unit is working at present. Not planning any long trips for a bit anyway.

I can always stick Milner unit on or tap Mr Karl up for one if it goes pear shaped. I will whip it off and give it a clean too, it is rather encased at the second and it may be filth that is causing the problem.

Once I have finished my wheel carrier that is.

Chris

 

[frank rabbets]

Hi Chris

Please please please try the same test with the inlet heater disconnected. The voltage in mine could never cope with the heater and only recovered when the heater cut out. I've disconnected my heater now, in view of my current motoring habit s which is all cold start. Batteries voltage and other electrical equipment is much livelier. I've had my LC for 15 years now and it only had 30,000 miles on it. The inlet heater has always drained the batteries on repeated short journies. I took it to Toyota, who actually had an expert, and he said this design was always being complained about. They swapped the whole loty out under warranty but nothing changed. Thinking of disconnecting the heater on my 100 but it does not seem to have such a bad effect on voltage.
I took the alternator to bits on mine and there were several connections which could give a problem although everything was perfect. clening the slip rings and brush holder helped the output. Very simple job and you do not need to know anything about electrics. Take a pic before you pull the ring pack off as this has to go on the same way.
Frank

 

[Gary Stockton]

Probably worthwhile stripping and cleaning out all the mud that's in there - cant be helping much!

 

[Chris]

Hi Frank. Inlet heater? You'll have to explain that one. Didn't know I had one! You don't mean the glow plugs?

Thing is that I have never had a problem with the voltage in the past Frank. It's quite recent. I have a digital voltmeter in the cabin and it started reading low. In terms of stripping alternators, got the T shirt on that one. Have rebuilt several in terms of bearings including the Wife's Corolla. Quite happy having them in bits. I draw the line a gearboxes but anything else I]m fine with. I shall get it off and give it a clean. It really is a mud cake at the minute.

We'll see.

Chris

 

[frank rabbets]

Hi Chris
Mine is a 24 valve 1996 and there is an inlet manifold heater above the vertical rubber turbo pipe. It is a square sandwich about 4 inches x 4 inches with a large cable feeding it. It stays on for about 1 minute after starting and as I say it really drains the batteries. Are you sure your voltmeter is OK? If she starts easy I would have thought batteries were charged OK.

Good Luck
Frank

 

[Chris]

Mine is a 12v. I don't think I have that.

The batteries are around 12v. The output of the alternator is around 13v at best so of course it starts. But the output is supposed to be 14.4 isn't it?

So it's running fine, starting fine, stopping fine. But it's not right. When winching without the engine running, it's clear that the batteries are not full. If that makes sense. They start to tail off quite quickly. Whereas before, you could do a full recovery off the batteries. Alternator is not giving the right output. It's as simple as that. Not a fault with my meter (s). It simply isn't kicking out what it should. I can do 20 miles and it's still not working properly so it's not some warm up circuit somewhere as far as I can tell. We'll see more after I wash it out in the morning.

Chris