battery and earth cable getting warm

[87diesel]

Hi all,

87 Caravelle, JX engined TD.

As the title says, the battery and negative cable on our van is getting warm and goes flat (now disconnected as i assume we have a short somewhere). I have had a search around on here and found lots of electrical niggles but none such as this and electrics is not my strong point, so hoping someone may have some experience of this. I will be going through the basics of cleaning earths etc at the weekend but wondered if anyone has some other pointers?!

To give the full picture, the first knowledge of this was the battery was flat on our van a couple of days ago, had ignition lights, glow plug light went off as it should but not enough power to turn engine. Charged battery, reconnected and off we went. Went to start it again a couple of hours later and flat again but no ignition lights this time. Put a different battery on and away we went, got home and later had a look around and noticed the battery and cable were warm and no ignition lights again.

Other than this everything appears to be functioning normally, starts straight away, lights work etc. I can't tell whether the starter is slow as it fires up pretty much instantly. Any info/pointers of common problems will be much appreciated.

Thanks, Chris

[v-lux]

1st, test the output voltage from the alternator and make sure its about 14v

2nd, clean your earths and make sure they are making good contact.

Usually, if you've got stuff getting warm then it's because of resistance (like a bad earth).

[California Dreamin]

You need to check the amp draw by putting an ameter in series (terminal disconnected).
Only problem being, the warm leads indicate substantial current flow so the 10amps of an average multimeter is not going to be adequate. In the trade this would be measured with an 'amp clamp' (magnetic induction clamp) that is placed around a main battery lead and measures amp flow without actually putting the current through the meter.

Martin

[87diesel]

Thanks for your input V-lux and Martin. I've had a look today and I think the problem lies in the alternator.

I had a nose around for poor connections before i tried anything, connected the battery up and started the van and i am getting erratic readings between 11.5 & 13v back from the alternator..... Goes up and down when you rev it, although i only acheived 13v once.

The other thing i noticed was that when connecting the negative terminal i got a normal slight spark, but it stuck slightly if i touched it on and off and with a slight cracking sound.

After running it briefly i had warm terminals and the back of the alternator was also warm. I removed the regulator and one of the contacts was sticking. Put it back in, and although not working and still with the erratic readings i can now take the terminal on and off without it sticking and making a cracking noise. I have disconnected the battery for the night but will check again tomorrow and go from here.

Thanks again, any further input appreciated.

Chris

[87diesel]

You need to check the amp draw by putting an ameter in series (terminal disconnected).

Martin, thanks for that. What would I do with the information from the result of this? Sorry if thats a dumb question but i'm afraid thats exactly what i am where electrics are concerned.

[California Dreamin]

I had a nose around for poor connections before i tried anything, connected the battery up and started the van and i am getting erratic readings between 11.5 & 13v back from the alternator..... Goes up and down when you rev it, although i only acheived 13v once.

The other thing i noticed was that when connecting the negative terminal i got a normal slight spark, but it stuck slightly if i touched it on and off and with a slight cracking sound.

You are quite right...the voltage output at the alternator should be somewhere between 13.9 - 14.2 volts.. 13 volts is far too low!

You say you have tried TWO batteries with the same results..but you don't mention whether you have leisure batteries in the mix as well? if you have, get them disconnected as there is a posibility that an internally shorting battery could be the reason.

An amp clamp will measure current draw (power flowing) from the starter battery. Point is: with the engine turned off there should only be a 'TINY' 200 - 300 milliamp draw (a fith of one amp) used by the clock and radio station memory. Anything higher than half an amp could be an issue when parked up for long periods.
It is clear from your description (that cracking sound) that there is a substantial and constant power drain which you need to find.

Once you have the meter connected, the usual diagnostic steps are to pull out fuses (from the fuse box) in order to isolate the troublesome circuit (the amp draw will just drop to practically nothing as the fuse is removed). Once you know which circuit is at fault you can start targetting seperate consumers on that circuit until the offending device/connection/short is found.

Martin

[87diesel]

Thanks for the info on the amp clamp. Does it make any sense that after removing the regulator, fiddling with it and putting it back that the cracking sound seems to have gone? From that I'm thinking of throwing an alternator at it, then go into further diagnostics if there is still an issue. On the other hand I don't want to blow a new alternator up?!

No leisure battery, btw.

[California Dreamin]

Cheapest part would be a new regulator/brush pack rather than the whole alternator.
You can pick these up for around £10.00 so definately worth a punt given those readings.

Something like this but you will need to check:

http://www.ebay.co.uk/itm/VW-GOLF-MK1-M ... %26ps%3D54" onclick="window.open(this.href);return false;

Martin

[87diesel]

ok thanks Martin, this has really given me something to go on, for now and future problems.

I'm going to buy an amp clamp today anyway to help confirm what is going on, rather than just piddling in the wind.

I will post the end result in the hopes this may be of future help to others.

Chris

[v-lux]

Just make sure you buy one that measures amps in DC as many of them only measure AC amps with the clamp bit.

DC clamp meters are fairly pricey in comparison.

[Oldiebut goodie]

I picked up an ex Royal Navy one - goes up to 650 ac and 900v dc and 1000Amps! - only £25.

[87diesel]

update....

Fitted new Alternator yesterday, checked battery voltage before starting 12.84v. Same when connected but started engine, battery then reading 11.4v.

Bring revs up and voltage goes to 14v, as i believe is correct?! Switch engine off, battery now reads 11.4v and warm cables and alternator. So fault still there, but only starts once engine has run.

In the time i had available i have now traced it as far as the main lead into the fuse box in the engine bay. Opened the cover and it smells hot and various bits warm to the touch, so need to go from there. As the problem starts once the engine has been run I'm thinking/hoping it could be a sticking relay maybe??

Watch this space....

[AdrianC]

Bring revs up and voltage goes to 14v, as i believe is correct?!

Yep, that's right.

In the time i had available i have now traced it as far as the main lead into the fuse box in the engine bay. Opened the cover and it smells hot and various bits warm to the touch, so need to go from there. As the problem starts once the engine has been run I'm thinking/hoping it could be a sticking relay maybe??

Watch this space....

I'd be looking at the earth leads, if you haven't already. Quick and simple test - get a pair of jump leads, and put one between engine block and body, one between battery -ve and body. Make sure you've got good solid connections.

[87diesel]

thanks Adrian, but earths are good. Further news...., went out this morning to investigate relays and connectors getting warm in the junction box in the engine bay and discover that some d***head has replaced what (i assume) should be fuse wire for the glow plugs with some normal wire, which is showing signs of having got rather warm. There is also a deteriorating repair to the wire feeding the glow plugs under some insulation tape.

All other wires in the junction box appear in good condition, it's just the glow plug feed thats showing sign of the insulation melting in places and the glow plug relay smells burnt and is burnt on one of the terminals (the same side as the burnt wire.)

I have begun releasing the section of wiring from it's clips, after lunch i'm labelling bits and take it out for inspection and repair. The relay seems to work but I think i will also replace that to be sure, as i guess of it isn't working properly this could cause a constant draw on the battery?.

[87diesel]

This will sound like an idiotic question, but i'm trying to obtain cable and connectors to replace the wiring from the junction/relay box to the glow plugs.

I have ordered a new relay and strip fuse, of which is rated 50amps. I assume this means that i need cable rated to at least that, but all the cable rated to and above this is much larger than whats on there, so i'm now confused.

The cable currently on there is original and has 54 strands (don.t know strand size) and measures 3mm across the conductive part and 5mm o/d. Does anyone have any advice or knowledge of where is best to get the right cable? I can get some cable 65/0.3 which is more strands and bigger than the original but says is only rated to 40 something amps.

I really do suck at electrics!

Thanks all.