Mk 1 Diesel Project

[Peter Jones]

I'm pretty sure I had mastered the multimeter,

There are many ways to use a multimeter (that's what the multi bit means)

Pop quiz. What do you use the AC (~) range on your multimeter for in the context of diagnosing auto electrical gremlins?

Pete

[Jarred]

you don't, you use the DC range for starters.

but I use the 20 V(--) range

[Peter Jones]

Sorry to crush your enginnering spirit there Jarred, but that's a 2 or maybe three phase AC alternator in your car.(alternators make - alternating current)

The AC is made into DC (more or less) by a bunch of diodes inside the alternator.

There will always be some AC ripple present when charging. The battery smothes most of the ripple.

If you can measure a lot of AC the diodes are shot and it's only a matter of time before the battery is too.

See? There's one new way to use that meter already.

Pete

[Jarred]

gah! smarty pants.

thats my new thing I've learnt for today then.

I'll give it a go tomorrow once the batt is charged, and the car is running.

actually, I should have read the question properly.

"diagnosing auto electrical gremlins"

Most I can do is check the voltage on the battery. Although aparently I can't do that either! hahahahha LOL.

[Preen59]

That's why Pete's a big shot Moderator and you're not Jarred.


Thanks for that tip Pete.. I didn't know that! (Never needed to..).

[gldgti]

That's why Pete's a big shot Moderator and you're not Jarred.


Thanks for that tip Pete.. I didn't know that! (Never needed to..).

more like its 'cos Pete is a big shot electrical Guru!

thanks pete, another trick up the sleeve

[Jarred]

So I went out to the garage this morning, to find the charger off, and a note next to it. "still charging at 4amp. NO GOOD" from Dad. Crap I thought.

Got my multimeter, and the batt measured at 12.3V, so I thought, bugger it, I'll give it a go. Pop it in the car and it starts up, no worries.

Get my trusty multimeter out, on 20 V(--) it reads 13.5V, indictating the alt is still charging properly. Whack it on 200 V(~) (smallest setting for AC) and it read steady at 28.6 V.

Current also measured at 0.00mA too.

I'm going to see if I can find the receipt for the battery, it's only about 14months old, so it shouldn't have packed it in by now.

EDIT: Found the reciept bought it 2/7/08, should still be in warrenty (spelling?) should it come down to that.

[ross_m]

Your car looks spot on! Simple but effective styling wins all the time.

How low do you think it is now in mm's?

I had to raise mine up a little when it was -80mm as the driveshafts were really close to the chassis. Mine has had a tiny notch cut out for clearance but wouldnt want to cut any more off and weld a pipe section in like some people have done..

[Jarred]

Hi Ross.

Cheers, I don't know exactly how low it is. I know it's not hitting the driveshaft yet though. I'd estimate at about 3 inches or 75mm of drop.

Once the suspension settles, I'm going to go out and set it up properly, make sure everything is clearanced etc.

[Peter Jones]

Get my trusty multimeter out, on 20 V(--) it reads 13.5V, indictating the alt is still charging properly. Whack it on 200 V(~) (smallest setting for AC) and it read steady at 28.6 V.

Current also measured at 0.00mA too.

That's a lot of AC. I wouldn't expect more than about a volt or so. You might have a shorted diode in your alternator. An oscilloscope would be the next diagnostic tool I'd apply. The wave form will quickly give away what's happening.

0.00mA ? Where and how did you measure this?

Pete

[Water Boy]

That was part of my Yr12 Physics exam...

Oscilloscope: a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage (horizontal axis).

Geeeeeeeezzzzzzzz im gooooooooooddddddd

[Spyda]

That was part of my Yr12 Physics exam...

Oscilloscope: a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage (horizontal axis).

Geeeeeeeezzzzzzzz im gooooooooooddddddd

NEEEEEEEEEEEEEEEEEEEEEEEEERD

i cant talk i did yr12 physics in yr11 haha

[Jarred]

Haha James, but I do know what an os-silly-scope is. I'm supposedly being an engineer remember

Pete, this was the reason for checking the current:

if your multi meter has amps select 200 mamps
remove one battery lead conect multi meter to battery post and
the other lead to the lead
have everything off the multi meter should not read over .04 mamps
if it does remove one fuse at a time till you find the curcuit with a drain
hope that helps you Jarrad

Actually, I did it wrong anyway, so ignore that anyway.

Should I try that spare alternator that you gave me, and see if the AC V drops down?

[Water Boy]

Haha James, but I do know what an os-silly-scope is. I'm supposedly being an engineer remember

Its like one of the only definitions I remember from the exam

[Peter Jones]

Should I try that spare alternator that you gave me, and see if the AC V drops down?

Yep.

Also look for voltage drops with that shiny new DMM.

Check the voltage between the body of the alternator and the -ve terminal of the battery for example. It should be 0.0v. If it's anything else, start replacing earth straps and cleaning contacts until it's 0.0v


Pete