RichardStobo

My Cl keeps burning up alternators,original went dead , new one lasted 6 months third one lasted two weeks . Think it might be the battery but anyone got any other ideas what to look for

Welwynnick

Did you try putting a voltmeter on the battery with the engine running?

Did you get you money back with the failed replacements?

It's usually a bad alternator that kills the battery.

Nick

RichardStobo

Yes I did get everything tested ,Alternator had no output , battery was showing 80% charged even though it had been on charge for 2 days and showed full charge, with the engine at 2000 revs it was only showing 11 volts . My thought are that the alternator was working to hard running everything and trying to charge the battery and got to hot,it had just driven 50 miles.i was wandering if there are any relay or other little gremlins hidden away that might be causing me problems
I did get my money back and luckily I can repair it my self,amazing how fast you can remove something third time around.

Welwynnick

I don't understand this bit. When the engine is running, you should see about 14.4V on the battery, regardless of anything else. If you only see 11V, that indicates the battery isn't being charged at all. That could be an alternator fault, or the alternator isn't properly connected to the battery.

Nick

RichardStobo

I know the alternator is at fault that's why I'm replacing them,it's why the alternator is burning up that I want to know.if there is no output from the alternator it will never show more than 12 volts.

Welwynnick

If your car is burning up alternators, that suggests it's the car, not the alternator.

I've never heard of a battery breaking an alternator.

If the engine starts OK, that suggests the battery is OK.

When the engine starts, does the ignition light go out?

When you replace an alternator, does the battery stay charged during normal usage, or does it go flat quickly?

Can you put a voltmeter on the alternator output while the engine is running?

Nick

RichardStobo

When replaced the ignition light goes out the battery charges and there was 14.6 volts at the battery on the volt meter. Every time it failed I was traveling between 50-70 mph and there was one flicker of the battery charge visit workshop light then it came on permanently.the battery was still charged ,even replaced the voltage regulator on the first one as they were supposed to be iffy,to no avail

Welwynnick

What voltage do you measure across the battery with the engine running, and with the visit workshop message showing?

14.6V would indicate that the alternator is charging OK.

If you have a visit workshop message, I would get an OBD2 code reader, and get the fault code. Simple ones are cheap. Everyone should have one, especially W215/220 owners.

Nick

RichardStobo

With the visit workshop light on it measures 11and I will get on of those readers