Oh dear...

For all electrical questions; Alternators including fitment; Light connections/wiring; Instruments; Gauges; MFA; Heater blower (not coolant related) issues etc etc.
Forum rules
Hints, tips and guides for repair and modification - the FAQ section on the main website is worth checking first for information relating to common faults and technical help. Useful posts and guides will be added to the FAQ http://www.sciroccoregister.co.uk/scirocco-faq
G Beats
Posts: 1067
Joined: Sun Jun 21, 2009 12:19 am
fill in the right answer: 10
Contact:

Re: Oh dear...

Post by G Beats »



G Beats.Been into MK 2 V.W Sciroccos since 98.Now on my fourth MK 2 Scirocco. R.I.P two MK 2 Scala DX Engine's.Sold GT 2. No longer have a mk 2 v.w Scirocco as it was stolen back in February 2020 .Or another one know have a 1980s BMW.
User avatar
wasted
Posts: 490
Joined: Wed Apr 01, 2009 11:29 am
fill in the right answer: 10
Location: Bristol

Re: Oh dear...

Post by wasted »

Right, just to check this...

Fitted the new alternator today, and found that it had the old-style connections on the back, so had to crimp on spade connectors to get around this (the original has ring terminals). So that was the fat red wire to one of the larger paired 'B+' terminals, and the thin blue wire to the 'D+' terminal.

Start the car up, and all seems fine - then started measuring voltages.

Voltage across the battery reads +13.82V. Seems good.

Alternator body to the +'ve terminal on the battery - +13.87V. Good.

Then tried to measure between B+ on the alternator to +'ve terminal on the battery, and got a massive spark as soon as I touched the lead to the terminal on the alternator. Not so good. Held it there, and the spark died down - touched to the +'ve on the battery, and we only have +0.03V. Not entirely sure this is good :cry: Does this mean that no voltage is going from the alternator to the battery?

However, having had the engine running for about five to ten minutes, the voltage across the battery appears to be fine. Sitting around +13.80V, and going down but then climbing back up again, so seems to be charging. Also, no ignition light on the dash when running.

Does anyone know if this sounds normal? Not really sure what I'm looking for here.


'89 Scala 1.8i - Daily drive, Work in progress!
colsy
Posts: 3
Joined: Wed Apr 08, 2009 12:44 pm

Re: Oh dear...

Post by colsy »

Hi Mate,
PM'd u back.
Sounds to me like your alternator is working, I cannot explain the 0.03V problem, possibly becasue the terminals you chose belonged to seperate circuits? you could be picking a flux up from the alternator it's self, hence the very low V...I'm just guessing to be honest, I'm no sparky. The alternator seems to be working tho yes? if you test the voltage across the battery with the car off you should read around 12V yea? with car running again reading across the battery you should see around 13.6-14.4 V..which you are? HOpefully someone can confirm that. Anyhow, if it turns out that the Alternator isn't doing it's job, I will refund you matey, no problem.
Col.


User avatar
wasted
Posts: 490
Joined: Wed Apr 01, 2009 11:29 am
fill in the right answer: 10
Location: Bristol

Re: Oh dear...

Post by wasted »

I think you're right. Having read up on things a bit, the alt +'ve to battery +'ve apparently tests for a voltage loss - if it's anywhere above 0.3V it's actually a bad sign.
The main thing is the voltage across the battery I reckon, as you've suggested - as long as it reads above 13.4V I think I'm good. Thanks for the unit - and the advice!


'89 Scala 1.8i - Daily drive, Work in progress!
Post Reply