Electrical advice needed

[4wheel]

Selectricity

Not sure if this will be of any help but some years ago had a similar problem.Turned out to be a bad earth connection between engine and chassis.Almost exactly the same symptoms as yours.Some vehicles have an earth strap between the two and dirt/rust can cause a poor connection.Took me ages to sort out and only noticed it when retrieving a dropped spanner.Just a thought,good luck.:thumb2

 

[melissachels]

oh this is a pug lol check the tensioners r gd, crankshaft pulley, ect may b one of them causing it

 

[11redrex]

Gotta wait for my hands to heal before doing any more work to it, the power steering pump is a seriously fiddly barsteward to remove and refit. Three mounting bolts, two of which can only be accessed from the side, through the pulley, with an allen key, and you can't see them, so it's got to be done by feel and guess work, and there's no room for a normal allen key so you have to use an allen bit and a spanner, and if you drop the allen bits it falls onto the alternator and sticks to it, and you can't see it to retrieve it, so you have to feel around with your fingers and there's a pointless bracket in the way that catches the back of your hand every time you go near it. The same pointless bastard bracket is also in the way when you take the tension off the pulley and the spanner slips and you smack your thumb against it.
Did I mention it was fiddly ?
Honestly, I can't be bothered with it any more. One 8mm bolt and the neg lead is off, flick the catch and the pos lead is off. No problem.
:doh:thumbs:nenau:augie:nenau:naughty:doh
should have mentioned, you need to remove the power steering pump to get to the alternator

 

[11redrex]

Right,, connected the battery this morning, showing a green indicator and 12.7 volts. Tried the amp drain test again, nothing. Left the DVM across the terminals reading volts and they've dropped to 12.4v, in the time it took me to remove the front anti roll bar from the maverick.
Nothing in the car is on.
I disconnected the wires going to the alternator (one small one going to a sensor on the engine block, one larger one going into the loom) and got a spark off the larger one. Can't see a diode anywhere on it to disconnect.
The battery is clearly discharging itself, I just don't know where to ?????
Time for a coffee.

 

[andrewk]

As suggested by someone else, your best bet is to connect an ammeter (DMM on a 10amp current scale) in series with the battery - and then start pulling fuses until the current falls to zero.

One thing to note - if the battery is good and fully charged (12.7v) but drops to 12.4v in a very short time with no load, it suggests that the current drain is high. It might be as well to put a 12V bulb in series with the DMM leads, to limit current so as to avoid risking screwing your DMM (not likely but possible).

Andrew

 

[11redrex]

Assuming you haven't read the rest of the posts, I've already done the DVM thing, with no reading. Maybe I'll try the bulb idea (acting as a resistor ?)

It's now showing 12.26 volts.

 

[andrewk]

Assuming you haven't read the rest of the posts, I've already done the DVM thing, with no reading. Maybe I'll try the bulb idea (acting as a resistor ?)

Let's take a step backward here and pause for breath ..........

If the battery voltage falls quickly (below 12.7V) when it is not connected to the car then it is goosed - end of story. Go and buy another battery.

If the battery is not goosed but the voltage falls quickly when it is connected to the car, then there MUST be a current drain - and it must be substantial (lots of amps).

There should be a small current drain from the battery all the time anyway (clock, immobiliser, alarm, ecu, whatever) - maybe 10-20mA and you should be able to measure that. If you read ZERO then either the meter isn't working or it isn't connected properly.

Andrew

 

[11redrex]

Battery voltage falls when connected to the car.
I think the meter meter works, as it shows voltage when tested on the battery.
For the amp drain test, I'm putting the red probe on the battery negative lead, black probe on the battery negative post, DVM set to 10A on the scale, and with the red lead in the 10A hole on the DVM, reading 0, expect when I remove the probes, the reading goes up to around 10 for a split second. ????

 

[andrewk]

I'm putting the red probe on the battery negative lead, black probe on the battery negative post, DVM set to 10A on the scale, and with the red lead in the 10A hole on the DVM, reading 0, expect when I remove the probes, the reading goes up to around 10 for a split second. ????

OK, I've just done the same and get a reading of zero also. If I reconnect the DMM probes to read up to 200mA and set the range to 0-200mA, I get a reading of 36.8mA.

What do you get? If it is zero then your multimeter doesn't work.

Andrew

 

[andrewk]

I bet your multimeter has a switch (slider?) that allows you to switch to AC or DC readings. You haven't by any chance got it set to read AC have you? If you have, can you set it to DC and try again.

The penny dropped when you said that the reading momentarily shot up to 10amps when you disconnected the probe. Really dumb on my part not to ask - it should have occured to me before. Still, what can you expect of smart arse electrical engineers .........

Hangs head in shame

Andrew

 

[11redrex]

No switch on mine, it's got a dial that you click round to whatever reading you want, ac volts, dc volts, amps/m.amps, ohms, audible alarm, one "COM" hole for the black lead and two other holes one marked 10A and one marked 600ma, ohms/volts/ma. this : http://www.westmeters.co.uk/product...ICAL MULTI METER&price=RRP £15.95&code=NO:169
Don't know about setting probes to read certain ampages, yours must be posh. Put the red lead in the 600ma hole on the meter and changed the dial to 200 and still nothing, not shooting up when I remove the probe from the battery terminal either.
Had enough for today, got the maverick in bits now as well so possibly no car at all !

 

[11redrex]

Really appreciate everyone's help with this BTW, getting a bit frustrated with it though

 

[andrewk]

Put the red lead in the 600ma hole on the meter and changed the dial to 200 and still nothing, not shooting up when I remove the probe from the battery terminal either.

I don't believe in magic. If the battery doesn't go flat off the car - but does go flat on the car then there must be a measurable current drain.

I think you need to verify that the meter is working on the DC current scale. Just get any AA (or AAA) size alkaline battery, set the multimeter to measure 10amps and just connect the probes directly across the battery (yes - just short circuit the AA battery). I've just done that and get 2.96amps with a new Duracell Plus (so it must have an internal resistance of around half an ohm). If you have connected the meter properly and picked the right scale and get a zero reading then it isn't working right. The multimeter presumably needs batteries to work. Try changing them and try again.

Sooner or later, you'll get a current reading when you use it to measure the short circuit current of an AA Alkaline cell (even if you have to bin the meter and buy another). Once you get there, then we can move on .....

As an aside, the meter I have ain't "posh". It must be 15 or 20 years old - a Maplin M6000. I bought it at the time because it was cheaper than buying a Fluke.

Cheers
Andrew

 

[11redrex]

I think my meter might be up the spout. Did the same thing with a new battery. 0 reading set to 10A, then shot up to 18 when I removed the probes. :nenau

 

[andrewk]

I think my meter might be up the spout. Did the same thing with a new battery. 0 reading set to 10A, then shot up to 18 when I removed the probes. :nenau

Progress

Andrew

 

[geoffdown]

I think my meter might be up the spout. Did the same thing with a new battery. 0 reading set to 10A, then shot up to 18 when I removed the probes. :nenau

Might be fuse in the dvm gone

 

[11redrex]

it reads dc and ac volts, and ohms, but the audible alarm doesn't do anything, and as before the amps only read after I remove the probes from the terminals. Time for a new one I reckon.....

 

[andrewk]

There is a way in which you can check the current drain very approximately, even though the multimeter doesn't work on the current scales.

1) Go find yourself a 12v bulb of some kind (say a 21W indicator)
2) Connect the bulb in series with the car battery (i.e. batpost > bulb > lead)
3) Measure the voltage across the bulb

If you use a 21W bulb, then its resistance will be in the order of 5 or 6 ohms (7 ohms hot but resistance increases with temperature). For the sake of the exercise, assume that it's 5 ohms.

With 40mA flowing through the lamp (the drain current on my Patrol), the voltage across it would be around 200mV. If it is hugely more than that, you can start to remove fuses until the voltage across the lamp falls.

Does that sound like a plan??

Andrew

 

[11redrex]

sounds like the video I saw on youtube, except he had a resistor instead of a bulb, and measure the voltage across that. too late now and working 16 hours tomorrow. Maybe friday.....

 

[andrewk]

sounds like the video I saw on youtube, except he had a resistor instead of a bulb, and measure the voltage across that. too late now and working 16 hours tomorrow. Maybe friday.....

I only said bulb because I thought it was more likely that you'd have one handy.

Andrew