Greetings all, new user, and i love all of the great info. I just bought a 78 coachmen camper conversion on a b300 chasis with a 360 engine. It had a bad alternator belt and while replacing it i pulled all of the belts off. now i can't get the AC compressor belt back on. There is an idler pulley that i would expect to be a tensioner, but i can't figure out how to loosen it. I don't even know if the AC works but i'd like to get the belt back on and find out. My chilton's will get here in a couple of days but was hoping somebody could help me out in the meantime.
B-300
03-08-2007, 12:29 PM
If it has OEM air-conditioning ther should be 2 belts that go around the crankshaft to the alternator and A/C pump. The idler is there to keep the belts from oscilating and the tension is adjusted by the alternator pivot.
If it has aftermarket installed A/C there are many configurations and pictures would help.
--B-300--
soybot
03-08-2007, 02:31 PM
I think i understand now. I noted that the alternator and AC each had 2 grooves, (and the AC definitely looks OE) When i bought the van, they each only used 1 of the grooves. All three grooves on the crank were used. If i recall correctly, one went straight to the power steering pump, one to the alternator, and the third to the AC, over the idler. So, if i understand correctly, what i should have is:
1 belt from crank straight to the power steering, the other two both go from crank to AC to idler to alternator.
Sounds like i need to do some measuring before heading back to buy some new belts. Autozone has like 7 different lengths in their computer, so the best i could do at the time was try to match what i had.
thanks for the info!!!!!
B-300
03-09-2007, 12:47 PM
My van doesn't have A/C, but as the power steering goes straight to the crank. (like yours)
It sounds like you figured out a method that will work... later models with A/C Have 2 belts over the crank, alternator and A/C pump.. They also had the power steering belt run over the water pump/fan. It sounds like you figured out how to run the fan with the third belt
I would have the parts person look-up the belts for a '71 and '72 with A/C to see which belts are the same. Also if you have the old belts still bring them to the store for comparison.
--B-300--
Ram4ever
03-09-2007, 07:16 PM
My '81 B-250 w 318 & AC has the two belts over the crank pulley, alternator pulley and AC pulley like what B-300 mentioned in the above post. I would think that you should have the same configuration - both of the alternator and AC pulley grooves occupied.
I had to take the belts to the parts store, and after taking into account the stretch they had accumulated and taking a best guess from among the numerous sizes in their computer, I had to actually spin the alternator pulley by hand to walk the belts on. -And that was with the alternator mounting bolts so loose on the alternator that it was almost flopping! I doubt I'd have ever got both belts on the alternator if the mounting bolts were tight.
When I tightened up the mounting bolts, and tensioned the belts, the correct tension brought the alternator a bit more than 1/2 way out the adjustment slot. So, -I'd say loosen all of the alternator mounting bolts, even remove some if necessary, then install the belts, snug up the mounting bolts and then tension the belts.
Chump
03-10-2007, 04:14 PM
Will make a difference if you have a 60amp alternator vs a 100amp alternator. If the old belts still have a number on them, they should be able to cross them over correctly. The number indentifies the width and length.
I definitely have the 60 amp, i sketched out what my arrangement looks like. i have attached my sketch of the pulleys, the numbers inside the circles indicate number of grooves (BTW how do you insert images into message body?). oh i also figured out that this is a 400ci engine, and is a 78 model. I went to the auto store and they gave me the what the computer said, and like you said, they are on the short side. I'm not sure if they'll go on even with the bolts loose, (although i'm going to give it a try). any feedback would be greatly appreciated!!
Chump
04-07-2007, 04:55 PM
Will the power steering belt fit correctly?
The reason the alternator belt probably does not fit is because of the idler pulley. I'm very famalier with that pulley and it was not common on most Dodge trucks but was used extensively on the car line to control belt whip when 2 v-belts were used on the alternator. My suspicion is that the original alternator may have had a 2 groove pulley on it. You can get the alternators with 1 or 2 grooves. what are the belt part numbers and brand that you purchased?
Chump
04-07-2007, 06:00 PM
The part number determines the size and each manufacturer may use different numbers to represent this. This is why I asked you the above questions. Any good auto parts store will be able to get youe the correct size or just ask Autozone for a longer belt.
Here's an example...
Belt part# 17340
17= 17/32" width at the top of the belt.
340= 34.0" long
Belt part# 15343
15= 15/32" width at the top of the belt.
343= 34.3" long
