Club 80-90 Forums

I have fitted a new battery today and I also have a cheap volt gauge that fits in a cigaret socket, when I turn on the ignition and the glow plugs cut in (did I mention it was a diesel?) the volt meter reads 10.5 volts until the they cut out when it reads 12.1, van starts on the turn of the key runs for a minuet or two then meter jumps up to 13.5 all good so far, but switch on the headlights and the reading drops down to 12.1, still with me? thanks.
My problem is a mechanic and Wiki say it should be 14.5 charging? To add to my dilemma the voltage reader on the leisure battery reads 13.5 all the time the engine is running and 12.6 ish when idle.

Could someone please tell me what voltage I should be getting, thank you?

Old cables and poor connections will result In a voltage drop where you are measuring the voltage.

If you measure the voltage at the alternator you will see your 14+ volts.

Now measure this at the battery and you'll see a little less but hopefully not too much less. If you do then cleaning up connectors or replacing the big cable will help.

Measure this further along the cuicuit and you'll see even more voltage drop at the cigaret lighter, headlights etc. Again it caused by poor connections etc.

You shouldn't see any drop to speak of at the battery - it only a foot or so from the alternator. I had a 0.5v drop in mine so replaced it. The old cable was corroded in the terminals at both ends due to crimping rather than soldering them. If you have an older voltage regulator in your alternator it may be set at 13.8v to start with.

The alternator was replaced in 2010 as I wrote that on it and I can still just about make it out, I was pretty broke back then (nothing has changed) so I may well have bought a cheap GSF or Justkampers replacement, should I replace the regulator or the brush pack?

Check the voltages first. Alternator output to engine, this should show what regulator is set at. Alternator output to chassis. Then alternator to battery negative and finally battery positive to negative. That will then tell you if there are any voltage drops in that area. Then you can check if there is a voltage drop between the battery positive and the cab end. Quite simple really to track down where you are losing volts.

If you don't have one, then a multimeter is a very very handy bit of kit for any electrical testing. Something like this, but there are much cheaper alternatives :

http://www.maplin.co.uk/p/uni-t-ut151c- ... eter-n55ec" onclick="window.open(this.href);return false;

Oldiebut goodie wrote:You shouldn't see any drop to speak of at the battery - it only a foot or so from the alternator. I had a 0.5v drop in mine so replaced it. The old cable was corroded in the terminals at both ends due to crimping rather than soldering them. If you have an older voltage regulator in your alternator it may be set at 13.8v to start with.

Yes sorry I was thinking petrol battery location; which is at the front of the van!

Thanks guys I think I need a proper volt meter to be certain.

Well...you do have some pretty spurious readings, however, as others have said, measure properly with a known good digital multimeter. Measure across the batteries (just off idle..say 2,000rpm) and directly at the alternator B+ output terminal...Report back.

Martin

Thanks, I got the retired Electrician from down the road to bring up his antique but accurate volt meter, the results were.

New battery nothing on 12.6v
Battery with ignition on and glow plugs warming up just bellow 12v
Battery with engine just started 13.5v
Battery with engine warmed up 14v
Battery with headlamps on slightly under 14v (he could not make out how much but he said the needle moved

Alternator after first start up 13.5v
Alternator warmed up 14v
Alternator with headlights on no noticeable difference.

I am not sure but that probably is not too far off what it should be?

Oldiebut goodie wrote:Check the voltages first. Alternator output to engine, this should show what regulator is set at. Alternator output to chassis. Then alternator to battery negative and finally battery positive to negative. That will then tell you if there are any voltage drops in that area. Then you can check if there is a voltage drop between the battery positive and the cab end. Quite simple really to track down where you are losing volts.

You seem to have missed just about all of the above!

I did, alternator to engine was 13.5v at start up and then 14v Alternator to positive was just under 14v and I was not sure how I was going to check to the cab and I forgot alternator to negative.

Alternator to engine 14v
Alternator to negative battery ?v
Alternator to chassis ?v


Alternator to positive should be 0!

One result is of no help in tracing voltage drop.

Ok thanks, didn't really grasp it and the electrician was a ships spark so he knew about DC but was unsure about vans, I will try again.

I bought my Merc bus from a retired ships engineer - everything he touched he bodged. All the wiring was just twisted together for joins. The rear brakes were worn down to the metal and the front pads were detached from the backing and just jammed when applied. Someone's former occupation isn't an indication of ability. ( A ship's sparky will be more conversant with 110v A/C which was the common voltage on board but nowadays more likely to be 440v)
Get yourself a cheapish multimeter and do it yourself - the meter will get plenty of use if you are keeping the van. These vans need the personal touch. The more that you do yourself the more you are in tune with how it is behaving.

If you had done all that I had listed you would be able to see where there are voltage drops which would be an indication of dodgy connections and the like. Your running voltage starts with the alternator hence starting the checks there. Alternator to engine will tell you the base alternator output voltage, alternator to chassis compared to the base voltage will tell you if there is a problem with the engine earthing strap and so on.
You'll get there eventually.