Scirocco Register

Last summer I purchased a Motorola 55amp alternator for my Rocco in the belief that the old Bosch one had gone.

When I fitted it, it gave me a charge of 13.6 reading across the battery. Not that good, but adequate. I stuck with it.

The other thing I noticed is I had to rev the car to about 4000 rpm to actually get it to kick into life.

I haven't actually driven the car that much since then - but upon investigation earlier, I noticed that the fan belt was a bit loose. Tightened it up . Started car, battery reads 11.8v. revved to 5,500 rpm. Battery still reads 11.8v. Connections are clean to alternator (I cleaned them up when I fitted it). Fan belt is tight although it seems to loosen up gradually for some reason.

Bloody Motorola recon pile of junk. I'm assuming it's gone or malfunctioning, right? The battery is fairly new.

Is there any other reason it would be suddenly not working?

I don't really want to go back to GSF, have them refuse a refund, and get a replacement pile of junk recon alt. - what I'm thinking is it might be a better idea to look on this forum for a 65amp original second hand Bosch one that someones selling.

Thoughts?

Likely to be an alt problem imo. Bit of a sod.

jbo is selling a 55Amp one in the Classifieds section:

http://www.sciroccoregisterforum.co.uk/ ... =5&t=13407

sing it with me children..... CHECK THE EARTHS!

so right from the off it wasn't charging right, that should have told you that there was a problem. if it has toasted the alternator (possible) then there is probably a reason. has it got a guarantee on it?

you need to check the voltage at the terminals on the alternator. assuming you have a nice 14ish volt there, you then need to work your way back to the battery and find where the voltage drop is. you may find that some earths are corroded, or some earth cables have developed a high resistance causing a voltage drop, so you'll need to do some investigating.

as an example, if you get 14.2v between the main alternator +ve and the alternator case, but you're only getting 11.7v at the battery, then you've lost 2.5v somewhere in between. you may well find that if you measure the voltage between the battery negative and the gearbox you will fins a reading of 2.5v, indicating a high resistance of the earth cable which would need to be replaced. in practice, you'll probably find lots of smaller voltage drops all along the path from alternator to battery, all of whih should ideally be addressed

i had very similer problem and it turned out the little blue wire going to the alternator had gone high resistance. as this wire bassiccly gets the alternaor going at start up if it doesnt work this will be why your having to rev it to get it to charge, if you can get it to charge at all!
but as nate rightly said check your earths first.

Hello!

Sorry, this is a real necro-bump, so I apologise for that.

Due to certain circumstances, I had to take the car off the road as SORN for a few months, which is why I haven't replied, sorry about that.

I've now got it back on the road and the update is :

I found a break in the blue wire! 'Twas a bit hidden away but I followed it carefully and whaddayaknow.

I've temporarily fixed it with some connectors, and bingo, I've got 13.5v again from the alternator. Always nice to have found the problem and it costs pence to fix.

Now, my next question is - it's a stock ampage alt, er..... 45amp or something? Same as the car comes with. Like I said before, it's a direct replacement Motorola one.

Is there any way of improving on this 13.5v? Do I need a more powerful alt? I rememer the old original Bosch one put out about 13.5 as well.

Or I'm thinking would a good clean up of the earths and battery terminals etc. give me more juice?

13.5V is workable with, in my eyes, it will charge the battery, but it's always nice to have 14V. Or are all you lot with 45amp alts driving around on 13.5?

Oh yeah - edit - I don't seem to have to blip it now, it just goes straight to 13.5v on startup, which suggests maybe the blue wire hadn't built up a resistance?

Work thru the instructions in my post above. This will probably help you find the missing volts

Nate wrote:Work thru the instructions in my post above. This will probably help you find the missing volts

Ah yes, I'm with you.

Sorry, bit slow with understanding electrics. Thank you - I shall do when I've got a moment and see whether I can get this thing more efficient.