Alternator problems

[PhilBUK]

Has anyone had any problems with their alternator on a Leon? Just got my car 3 weeks ago with 14K on the clock (55 plate). In the last few days when it's cold the light stays on for about 1 mile before going out. I checked the voltage and sure enough it's about 12.6V with the light on and 14.3V with the light off. Sometimes when it's started up it goes straight out. Normally when it's been left standing overnight it takes the mile or so to go out.

Have just checked all the connections to the battery and alternator and tightened them up but it doesn't seem to have made any difference.

Other than it being a duff alternator anything else I should check before booking it in to be fixed under warranty?

 

[DPJ]

A coincidence that you posted. I was just going to do the same. (my car's an 02 1.8T 70k miles).

My alternator bearings are going. Has anybody any suggestions where to get a replacement (other than dealers). Its 120A.

 

[sureal]

Have you any way of getting the battery checked ? I had this prob before with another car and it turned out to be a faulty battery it may have a faulty cell which is causing the alternator voltage to be dragged down and after you drive it for a while after the battery slowly discharging overnight the other good cells in the battery get charged bringing the voltage back to a level that puts out the light, best thing id do is to maybe go somewhere and get a free battery check with a load tester.
Hope this helps

 

[The MoffMeister]

but the alternator charges the battery doesnt it? whens its runnning whats the voltage?

 

[PhilBUK]

Good question about the battery. I did have a problem when I'd had the car only a week or so. The fuel pump relay died. Coincidentally the battery was completely flat even though I'd driven 240 miles the previous day. I took it into a SEAT garage who fixed the relay under warranty and I also asked them to change the battery but they refused saying there was nothing wrong with it and it just needed an overnight charge. They claimed to have tested it and told me they couldn't change it as they wouldn't get their money back from SEAT if it wasn't defective.

With a dead cell, presumably I'd expect to see a lower voltage before I started it up. What voltage does each cell contribute to the 12.5V of the overall battery?

I'm surprised that a dead cell would pull the alternator voltage down so much. But I'm happy to be corrected.

 

[sureal]

One thing to try is to eliminate the battery altogether by removing the + once car is running taking care not to let the + positive terminal connector touch the bodywork etc, put a multimeter (if you have one) on the connectors and check voltage with car at idle with no electrical accessories on ie lights and again with them on if the alternator is sound you should see a drop in the voltage but not enough to put the alternator light on.

You could also check for AC coming out the alternator by changing the settings on your multimeter to AC and if it a manual ranging meter to the 20v range, alternators take their AC output and change it to DC via the rectifier/regulator that is built into them, if it is faulty you may see some AC voltage when you check, if you have a small reading of less than a volt and it fluctuates up and down then thats ok, if you get a constant reading of AC say for example 1.53v then your alternator may be faulty and I would get it checked.

That may explain the car battery getting some sort of charge but not enough.
It definately sounds like either the alternator or the battery and hopefully you will get to the bottom of it.

Again hope this helps.

 

[Big_daddy]

Get a tester like 1 i have, shows battery levels and alternator levels

http://www.seatcupra.net/forums/showthread.php?t=146309&highlight=battery

 

[Stan 24v]

Check the volts DC with the engine running, at the battery terminals mate. You shout be seeing over 14v.

Then check the battery once engine is switched off, and again after an hour, and then a few hours/next day. Write down what you get to see if its discharging.

 

[sureal]

Just had another thought, might be worth checking the actual output voltage coming from the alternator for the warning light when the cars running, if your car starts no problem and the battery and alternator are showing the correct voltages at all times maybe you have just got a faulty output signal, the cable to the warning lamp will be the thinnest of the wires connected to the alternator and should give a reading the same as the voltage at the battery terminals (engine running).

 

[PhilBUK]

Thanks for the suggestions.

I checked all the connections early yesterday and found the earth clamp on the battery was slightly lose. I tightened it up and since then it seems to have been OK on the 5-6 occasions I've started the car (even after leaving overnight). I wonder if the garage disconnected it when I took it in for the new fuel pump relay as they charged the battery overnight and perhaps didn't tighten it up properly.
I'm hoping that was it, but until we have another cold snap I'm not convinced.

 

[The MoffMeister]

yeah a loose earth can do that

 

[creid90]

Sorry to hijack the post but im not sure how to make a post of my own, anywho, i've got a problem, i had a sight bump a few week back and it broke the terminal off the alternator (dont think it fell off straight away) about 6 days after i rebuilt my front end i was out and the battery died which is when i noticed the broken alternator, i fixed the terminal back on n it was okay for another week at which point i had more problems and i realised the alternator was charging the battery so i changed it for a 2nd hand one, fitted it and took the + off the battery and the engine didnt cut out which tild me it was workin, but then a few days later it wasnt working, got another 2nd hand alternator and again a few days later that stopped working... does anyone know whats killing off my alternators?