MK2 1.8 Carb - Voltage Drain

[StuartGT2]

Hi all, picked up my first scirocco the other week, a 1992 GT2 1.8 Carb. The car had been sitting since last november and didn't have a battery so I got a good second hand battery and plonked it in. The starter needed abit of persuasion to get going but once it went she started up no bother and ran away fine.

The first problem encountered was the battery warning light stayed illuminated, I had a multimeter handy so I checked the battery voltage when it was running (just over 14v) and when it was stopped (about 11.8v). So all good there it seems, at first I was thinking just the warning wire might have corroded somewhere.

But after driving her home the battery went flat over night, I mean completly dead, no interior light not even sidelights. I spoke to the guy I bought it from and the best he could give me was he thinks there may be an earth wire missing going from the coil pack to the block or bulk head? Does this ring any bells? The only other thing I can think of is possibly the diode pack on the alternator is knackered and its maybe taking a drain whilst the car is off. This could be the what is causing both my problems.

Anyone got any advice? Could someone post a picture of there engine bay of a 1.8 Carb so I could see if I am indeed missing an earth. I've still to try and do some ammeter tests on the alternator to check if its the cause of the drain but I'm abit ropey when it comes to electrics, not 100% sure what readings I should be looking for. Any advice would be great.

Cheers

[ianaudia4]

It is your battery by the sounds of it. The alternator seems to be working if you are getting 14v when it is running. Only 11.8v when switched off? A charged battery should be reading 12.8v or so when the engine is switched off.

[StuartGT2]

Hi, thanks for the quick reply.
I'm pretty sure its not the battery, I may be a little out with figure of 11.8v . I put a battery tester on it at my work before it went into the car and it was very healthy. It had previously been sitting on a bench out of a car for over a month. Plus the guy I bought it from hinted something like this had hapened before to a previous battery.

I'll charge it back up and double check the battery. But I'm pretty sure its a voltage drain from a component.

Cheers

[ianaudia4]

Check your interior lights and radio then, you could just take out fuze number 3 and see what it is like overnight, narrows the search down a tad.

[Nate]

as you stand in front of the car there should be a webbing earth strap going from the right hand end of the rocker cover to the coil. never known this to cause charging problems though, it usually just causes missfiring.

if the battery warning light is staying on, this points to a problem with the charging circuit. would be worth connecting up the battery thru an ammeter with everything turned off to see if there is a parasitic drain that goes when you remove the suspect items (just pull the fuses one a time and see when it stops to idenify the problem) although i suspect you are right in thinking it is a problem with the rectifier

[Neillyboy]

Check your fusebox for corrosion and water ingress. I minor leak could be shorting something out slowly draining the battery & keeping the light on.

[StuartGT2]

Thanks for all the replies guys

as you stand in front of the car there should be a webbing earth strap going from the right hand end of the rocker cover to the coil.

Yup I don't have this, I can't say theres any ill effects when the cars running, but the accelerator cable is so slack its a struggle to get it over 60 so possibly not built up enough revs yet to notice that. Ill try and get an earth on it this week. Where abouts on the coil does it attach?

Just charging the battery right now, on further inspection of the alternator and after comparing it with my audi's, which is similar It seems that it may have been connected wrong, theres a big round nut that had nothing on it and the main feed cable was going to the small 8mm nut. On the audi the main feed goes onto the big nut and the signal wire onto the 8mm, I might try it the other way around. Although the charging systems look slighty different, it can't hurt to try.

Cheers

[Nate]

assuming your alternator isn't one with spade connectors on it, you should have a small blue wire and a mahoosive red one. the red one goes to the large nut that is marked 'B+' and the blue one goes to a smaller nut wich is probably marked 'D' or 'D+'

the earth lead just goes from the end bolt on the rocker cover to one of the coil mounting bolts

[StuartGT2]

Thanks for all the help guys, thanks nate, yup it seems the alternator was wired wrong, it was still giving out 14v, but obvioulsy draining it when it wasn't running.

Now shes running its time to get her to the garage to start on her, I feel like i want to rip all the elctrics and fuel lines out the engine bay, its a total mess and has lots of crap repairs.
The fun begins!

Thanks!

[Neillyboy]

I'm glad you got it sorted mate.