Alternator issues on MC8

[rcbeam]

The p/o of my MC8 took off the old 50DN when he had trouble with it.  He also removed all the bus heat/air except for the defroster heater, so all the big loads are gone.  He replaced the alternator with one from a truck, made a frame mount and drove it with two belts off of the rear puley (cam pulley I think?).  I have had the bus only a year, I had to replace the batteries because they would not hold a good charge.  I suspected that the alternator was not putting out like needed. Took it off and to a shop to test... sure enough it was bad.  I also asked him what size it was and he replied 75amp.  My friend that is the head mechanic at one of the local tour bus operations, suggested that I needed a 150amp and that 75 was too small. 

So I'm asking for any words of wisdom for you guys on what I should get to replace this alternator.  Also, is is ok to run it driven off this pulley?  Is the pulely big enough to get the proper revs on the alternator?  I only want to do this once, so I need to do it right and be done with it.  Bus is still all 24V.  I don't plan on doing running any roof airs/inverters off of it or anything like that... just lights and defroster and normal bus operation.

Thx ahead of time.

Russell
Lexington Ky

[chart1]

24v 75amp alternator is what I run and never had a problem. The only thing I run off 24v is starter, defrost, running marker lights. Everything else is 12v They cost 100.

[rcbeam]

Thanks Chart1 for that info.  Where did you mount your alternator?  Mine sits on  a raised bracket bolted to the street side frame member and runs off the small rear pulley.  Is yours the same?

Russell

[chart1]

When you open the back to the right where the old ac compressor sat

[luvrbus]

The  MCI 8 came with a belt drive or gear drive for 50D if the pulley is on the drivers side middle way up that is the factory drive you are good to go truck engines were belt driven at the top off the blower around 170 amps max.I would go for a 170 to 200 amps not going to be a big difference in price and they will last a alternator running at max like a 50 to 100 amps have a short life span as you just found out
Reading your post that is factory belt drive for the MCI 8 you lucky dog lol

good luck

[chart1]

Luvrbus.. You are so right on that one. I have replaced 2 in 9 years.

[luvrbus]

You did good Cory most people get around 25,000 miles from one

good luck

[gus]

75 amps at 24v is plenty for normal electric loads. That is the same as 150 amps at 12v which I had on my 4104 before I replaced it with a 105 amp one which was still plenty. However, it is a simple conversion with a moderate electrical load.

Since your huge bus system blower is gone you are not left with much of a load, that thing used huge amounts of power. The next biggest load is the marker lights but it is small compared to that blower motor.

[Chopper Scott]

I replaced mine with a 1 wire 24 volt alternator. I had to make a bracket to fit the original generator crap and eliminated the air tensioner with a turnbuckle. pretty simple upgrade...

[chart1]

Luvrbus... Like I said 2 in 9 years, which is about 50,000 miles which breaks down to 25,000 per alternator. WOW...You are not only smart but psychic.