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Alternator Problems?? - NeilT
Having spent the last 2 weekends fitting PAS to my Nan's 1995 Skoda Felica 1.3LXi I was very disheartended to find the biggest problem out of the whole job is the lack of charge on the alternator...

Having solved all the mechanical problems of fitting a PAS kit from a 1999 car (that when PAS became available on the Felica 1.3), which included a second hand alternator, I came against an electrical problem which is not my pet subject.

Symptom as below:

Start engine, battery charge light on dash is dim, rev engine, light get brighter.

1. check Voltage over battery with engine off = 12v
2. check voltage over battery with engine on = 12v
3. check voltage over battery with engine running, plus lights, blower, rear sreen, radio etc running = 10v
4. check voltage across alternator feed to battery, and dash light feed = 5v

I changed the regulator/brush unit over from the old alternator, and still no luck. The Skoda Spares place I got the kit from also confirmed it was charging ok before it was shipped.

I think it maybe an earth problem, although it could only be between the alternator and the engine block as the Starter motor works fine....surely this would have problems if it was the earth from engine block to body??

One thing I haven't tried is voltage between alternator and earth, also I haven't checked resistence between block and alternator.

I have now brought the car back to my house to solve this problem, having driven 80miles (crrying a spare battery and jump leads), and it doesn't seem to bad, taking only 3-4 amps on the battery charger. Clearly something is wrong, but what? I am stuck on...


cheers
Neil T
SEAT Leon TDi 150
Alternator Problems?? - Crinkly Dave
Sounds like the alternator isn't charging at all

Assuming it really is not faulty, aren't there some types which require a separate feed to supply the battery sensing? Must get my textbooks out
Alternator Problems?? - NeilT
OK, since last post a friend has checked it out in more detail.....I was doing it all wrong..:-)

Alternator is giving 13.8v
Battery is giving 13.8v when running
drive 5 miles with everything switched on, battery still gives 12+ Volts when engine is off...i.e is charging ok.

Test voltage between dash light (not pluged in) feed and earth 12-13v depending on engine revs.
Test voltage between dash light when pluged in to alternator and earth 14-18v dependig on engine revs.

That difference is what makes the light glow brighter as revs increase.... Faulty regulator????

Earthing is ok, about 0.02-0.04 ohms between alternator and body.
Neil T
SEAT Leon TDi 150
Alternator Problems?? - NeilT
Sorry, got info in last post slightly wrong……

With the dash light unplugged the alernator gives 13.8v
With the dash light plugged back in it gives 14-18v as revs rise…..

Possible short in light circuit when I removed steering column/ignition switch??

Neil T
SEAT Leon TDi 150
Alternator Problems?? - Peter D
Hi,

Sounds like you have lost one of the diodes in the alternator.
Go for a run with heater blowers , rear screen etc etc turned on.

Come home and get a mate to lift the bonnet and measure the battery voltage whilst you hold the engine revs at 2000 to 2500 and head lights on. Battery voltage should hold up at 13.5 to 14.2.

Other test bould be to use a scope to see that all phases were contributing.

Goto www.vtr.org/maintain/alternator-overview.html

For full description.

Good Luck
Alternator Problems?? - NeilT
We did go for a 5-10miles run with lights/radio/heater/demister etc om, and it was ok on return...:-(
Neil T
SEAT Leon TDi 150
Alternator Problems?? - Peter D
All you said was 12+volts when off

A fully charged battery at 20 degrees C will have a minimum voltage of 12.6 v after one hours rest.

Immediately after charging I would expect to see 12.8 to 13 volts for at leat 30 mins no load. If you only have 12.2 to 12.4 your alternator is faulty/ missing a diode thus charging with maximum load not holding up, thus the red light.

Regards


Peter
Alternator Problems?? - NeilT
The battery is giving out slightly more than 12v, but it has had alot of stop/starting of the engine over past 2 days, with only a 5mile drive to re-gain power. Then again the Alternator is giving out 14-18 volts when the dash light is connected, and 13.8v when its not... Having read the site at the above URL given earlier it suggests a battery fault....that might explain why the battery won't take less than 2-3 amps after a days charge....

I'm taking it to a local friendly motor factor tonight who will check the battery and alternator.... surley an alternator problem would have shown up in the car it came out of, which incdently was a low mileage (15,000), 1999/2000 car......


Neil T
SEAT Leon TDi 150
Alternator Problems?? - Peter D
Again you mention 18volts. Where are you measuring this. Is this directly across the battery if so the internal resistanc eof the battery is far too high and would imply a faulty cell or to.
Tell me how you and where you measute this voltage. The highest I have ever measured is 17.2 and that was due to a duff battery that only had one quarter of the amp hour capacity left in it and died if the temperature went to low i.e. minus 2 degrees.

Regards


Peter
Alternator Problems?? - NeilT
18v was the alternator output..i.e, across alternator "out" and earth. I had the battery checked last night, and it was fine......basically, what ever the alternator is giving out, if you measure across the battery terminals with the engine running it is showing 13.5 - 13.8v....... it just seems the warning lamp system is to fault, although I don't know what controls that system... The guy that tested it thought maybe that the warning lamp has a seperate internal unit to the regulator.
Neil T
SEAT Leon TDi 150
Alternator Problems?? - NeilT
More news, the compnay that supplied the parts are sending me a new another alternator FOC to see if its any better. At least it will tell me if it "is" an alternator problem, or something I have disturbed in the car. It should be here Friday, although fitting isn't planned till Tuesday as I have to go up to Suffolf after work to do it. The acr is back on the road at the moment with the dash light unplugged.
Neil T
SEAT Leon TDi 150
 

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