Alternator output

[tony_ack]

I've had a bit of a nightmare this week. Last Sunday night I was on the way to Oxford with work, when the lights started to dim, and then one by one, warning lights appeared on the dash. I opened the bonnet and the aux belt was completely free from the alternator - the tensioner spring had snapped.

 

I got the car recovered, and asked the garage to replace the tensioner, but also check the alternator pulley, as I know these can be prone to failing, taking the tensioner with it.

 

I picked up the car a couple of days later - they said they'd only changed the tensioner as the alternator pulley looked okay. The car was fine for about 50 miles, then on the motorway, there was a loud bang under the bonnet - it had blown a turbo pipe. I got off the motorway, temporarily resecured the pipe (it had blown at the intercooler), and went to start the car. The battery was completely dead. 

 

Luckily someone managed to jump start me. I rang the garage who told me that everything was fine when I left, and I was too far for them to come out to me. I found the alternator load wire had broken under the car, so temporarily fixed that, and managed to limp the car home.

 

I got home and there was smoke in the cabin. I popped the bonnet and there was smoke pouring out of the battery. I disconnected the battery and removed it from the car.

 

I swapped the battery for a new bosch one, and the alternator for a recon bosch unit. I fitted them today. After fitting, the voltage across the battery was 14.2-14.4v at idle. I took the car for a test drive, and when I got back, the reading was 14.05v (the voltage dropped instantly when the engine was turned off).

 

Is this normal, or is there something I else that might be causing a problem?

 

It's a Fabia VRS by the way, an early one. Both the alternator that came off (looked like the original) and the replacement unit were 90A

Edited 20 September, 2014 by tony_ack

[sepulchrave]

That's all normal, nothing to worry about.

[vindaloo]

I would guess it wasn't a VAG group garage?

[padi]

Your battery should have about 14.5-15 volts going into it when the engine is running and the alternator functioning normally with engine stopped battery should show around 12.6V. 

[tony_ack]

It was unfortunately just whatever garage could recover the car at 5.30pm and 150 miles from home.

I rechecked and voltage at idle was now 14.3v and dropped to 12.7v with the engine off. I'll see how it goes

[sepulchrave]

It was unfortunately just whatever garage could recover the car at 5.30pm and 150 miles from home.

I rechecked and voltage at idle was now 14.3v and dropped to 12.7v with the engine off. I'll see how it goes

 

That's perfect, you can relax.