Alternator Information

[Markbhai]

Hi All.

I am looking for some 'pre-information' before I diagnose my alternator as being faulty.

My battery was replaced last year as it was old and not retaining a charge.  This year my new battery has run flat a few times already, so I am suspecting the alternator to be at fault.  I plan on taking the car to Halfords for a check in the next few days, but was looking for some info on the alternator.

My car was built in October 1966 (230SL) so I suspect it has a 35W alternator, but I am aware that a 55W alternator was also produced. So my first questions relate to this:
1. Is it a straight swap if I replace a 35W with a 55W alternator
2. Are there any real world advantages of doing so (the car is stock except for my music system which will obviously draw more power)

I don't want the car to be off the road for too long as British summers are short enough so:
3. Does anyone know a UK supplier who can do a 'refurb swap'; or
4. Does anyone have a clue how long a refurb would take ordinarily?; or
5. (Long shot) Does anyone have an alternator for sale?

My alternative seems to be a new one otherwise, which I am guessing would be a few pounds.

Regards

Mark.

[Ron500E]

This is somewhat useless information to you but... I had mine completely rebuilt, at the best place in Chicago, for around $75 and it took less than a day and came with a 2 year warranty. I brought it in on a Monday and picked it up the next morning.
That should give you an idea as to what you would spend.

Ron

[Markbhai]

Far from useless Ron.

Thanks for the info...the timescales of a refurb alone make me think this is a viable option.

Greatly appreciated.

Mark.

[Shvegel]

You should have a red light on your dash to indicate charging.  Does it come on with the key in the run position(engine off)?  The light on the dash is part of the circuit that excites the alternator. It feeds it enough current to establish the magnetic field that allows the alternator to charge the battery.  A simple thing like a burned out bulb or a bad ground at the alternator can cause the alternator to stop working.

As for upgrading to a 55 amp alternator if you have not made any major changes to the electrical system like higher wattage headlights recently there should be no reason to upgrade the alternator.

[Tyler S]

First check to see if the system is charging. You should have at least 13.5 volts at the battery with the engine running. You also want to check the voltage regulator on the rt fender well. If it is at fault the light on the dash may not give you an indication of a problem. You are playing with fire if you upgrade from the 35 Amp alternator without modifying the wiring. The wiring to it is only 10 gauge and rated at 30 amps. You can replace the 10 gauge wire from the alternator to the starter with 8 or 6 gauge wire if you do decide to upgrade amperage. An appropriate amperage fuse link should also be added. If your system checks but battery reading is dropping with the engine running and your ancillaries (stereo system) on, then you may want to upgrade. The 35 amp alternators are available rebuilt.