Belt Generator

[Hermila Farquhar]

Wehave a 2001 Signature with a Onan 12.5 Model HDCAB11506A generator. Last year I had posted we had an issue with over temperature fault. Last year I cleaned the radiator fins and tighten the fan belt and the problem went away. We put over 125 hours on the generator after this work was done. The other day we had the generator running with all 3 roof top AC one and the generator shut down for over temp.

Last evening I pulled the top off of the Generator to check the belt and the tension looks fine. From what I can see the belt looks like it is in good condition, however it not easy to see. I can not find any record of the belt being replaced in the documentation we got with the coach. The generator has about 1900 hours on it.

I started the unit and the fan turns and it doesn't sound like the belt is slipping. I put the cover back on and I can feel air being push out he back end, however after a 1/2 hour or so the housing in the back area was getting hot to the touch. From what I can find the shut down temp is 230F. The max running temp should be 104F over the ambient temp. It was 70 last night and I had check the hose temp at around 185F.

Just wondering if anyone else has seen this issue. I'm trying to decide my next steps. I'm thinking about replacing the belt. It could be old and glazed and not driving properly. Do I replace the belt only or do I do the thermostat and water pump while I'm at it.

I'd say it depends how much you hate crawling under and opening the rear generator housing again. But since you have overheating issue, it might be a good idea anyway. Maybe I am lucky but with only few hours left to be at 4K, I only replaced the belt in that area but I don't consider it a huge job even if I had to do it in the field. Just as long as we make it out of this Oklahoma heat tomorrow, would not want to do it here today...

I wanted to give an update on my over-temperature issue. After I removed the top cover and was able to get in and get a better look at the belt, I found that the alternator pulley was not running parallel with the water pump and crankshaft pulleys. I proceeded to remove the back cover and found that the nut that fastens the bottom of the alternator to the block missing and the adjustment bracket on the top that allows for belt tension cracked. This allowed the alternator to pivot around the look bottom bolt, putting the pulleys out of alignment but the belt stayed tight. This misalignment caused the belt to wear on the sides as shown in the photo and eventually cause it have limited contact with the pulleys.

I went to the Cummins site to purchase a new belt and bracket. The was bracket was $27.00 and like other supply chain issue will ship sometime in the future. I tig welded the cracked one back together till the new one arrives. I priced out the belt from Cummins and it was $142. I had the original belt and part number by Bando. I did a little internet searching and found the belt by Bando from Diesel Parts Direct for $12.76. I purchased 2 of them, so I had a spare, for less than $50 with shipping. When the package arrived with the new belts, the packaging called it an Isuzu water pump belt. The Bando Part number is 8972249991 for Onan Model HDCAB11506A 12.5KW Generator.

Last week I finished reassembling and test ran the generator for about an hour with all three AC's running and had no issues. It worked fine over the weekend, however it was in the low 70's during the day here in Wisconsin so we didn't run the AC. Hope this information can help someone in the future.

I had Cummins/Onan replace ours. It had about the same number of hours yours had. When they brought me the old belt, it had places that were in shreds. It was shot and would have broken within a very short period of time. As it was, I was amazed it was still working. The generator won't run without the water pump working so I'd have it replaced as soon as possible. It is possible to remove the cover and get to the 7.5 KW Onan Quiet Diesel. If you have reasonable mechanical ability you should be able to do it yourself. I'm sure you can order the belt from Onan if you can't get it from an auto store.

Just bought one for our coach on eBay. Cummins part number I obtained from Cummins/onan. I found it on line but the shipping was more than the belt, my local dealer didn't have it in stock and again the shipping was expensive. We have a 2001 7500 Onan and the part number is 511-0235. I picked it up for $14.00. I tried the local Napa to cross the Cummins number but they couldn't.

I finally got around to changing the belt, I removed the top cover, driver side and rear cover toaccess the belt. Instead of stretching the belt to remove and install, I removed the pulley from the hub of the water pump.Thank everyone for the encouragement to self perform.Jim

Jim, changed mine today, I did the same thing you did. Unbolted the waterpump pulley, installed the new belt lined the holes up with a drift pin and ran the bolts in. It took me longer to remove the wall on the genset then to change the belt. While I was at it I changed the oil and filter, coolant, fuel filter, radiator cap, thermostat and gasket and the air filter. Ran it through a full warm up for an hour with both roof top heat pumps on for a test run when I was done

Carl, LOL! It sits outside all year, along side the garage on a gravel bed. Too many years of being a Mobile Fleet Technician. It only hurts my aching bones in the beginning of the winter season, then I adapt.

I'm looking to buy a generator belt for my B&S 16 Horse (320421-0134-01-7007291). The Briggs Number is 68878. Any search on that number only brings up Briggs manufactured ones costing $33.50 (Jack's Small Engines) and doesn't give any specs on the belt. I've searched the Simplicity number for it (122146) and come up with different belts around $14.00. (EX: Stens Aramid 38" x 3/8" x 7/32" 3L). I'm not finding any equivalent from the major belt manufacturers (Gates, Dayco, etc.) Anyone replace this belt with something they are happy with that they can provide a link to? I just don't want to get down the road and have to replace a cheap one after the drive shaft is installed. I've had good luck with the NAPA FHP belts, I may just go with the correct size and profile in one of them unless someone has a better suggestion. Thanks.

The Homelite bracket calls for a 37" belt vs 39" for the Simplicity bracket. The Homelite bracket positions the S/G a little lower and tighter to the Briggs engine. I've found each type of bracket on both tractor brands due to engine swaps over the years.The belt part number I have for the A/C Homelite bracket is 1607323, listed as a 37 1/2" belt, but a 37" belt works OK. Some have had issues when using the larger belt with an A/C Homelite bracket, the S/G swings out too far and the field terminal hits the hood.

I think I have three different types of "Large Frame" Simplicity S/G brackets laying around here. The early 10hp FDT's had a different pulley on the engine (3 piece steel) compared the the aluminum pulley's made by B&S. Some of these may have had differences in diameter resulting in different belt sizes.

The 39" belt is easy to put on. The 38" belt is more difficult to put on but when it is on, it tucks the S/G up tight against the engine, and does not stick out beyond the hood...gives a nice clean look to the tractor.

As always, thanks for the help. I'll take a look at the pulley and take it from there. At least I know I don't have to buy the expensive B&S one. For anyone thinking of joining, this group has saved me 10 times what I pay in dues!

To add to Racinbob's comments,

The belt driven units have bearings for the side load of the belt powering it. Units that are coupled directly to the engine probably can't handle that side load or at least do it for very long. BUT, you could add a shaft which is supported by bearings to use one. It would be a bit more work to do it but the generator heads are much more common and therefore, probably cheaper.

Harbor Freight was selling a 10,000 watt pulley driven gen head fairly cheap. You wouldn't be able to use the full capacity of it with a 14hp engine but how often will you need 10,000 watts of power all at the same time. Still, a 14hp should handle close to 7000 which is usually enough to run a whole house.

A little internet research on the subject will give you a good idea of what and what not to do if you decide to make one yourself

Actually John, directly coupled gensets don't have anything on the shaft side. The motor supports that end. Here's a pic of one I just sold. The shaft you see is actually part of the crankshaft that I cut off and there's nothing supporting that end.. I thought about a flange bearing but there wasn't enough length for a bearing that size (1 3/16"). I couldn't find a smaller tapered shaft and didn't have the machining capabilities to make one. With the right shaft a flange bearing could simply be bolted to the end of the case.

That's good info on running a 10kw with a 14hp. The 5kw Wheel Horse unit I has was plenty for our all gas home in Indiana. It's a different story with this all electric home here in Florida but as long as I used common sense I got by. I just looked at the Harbor Freight unit. It's 10kw surge and 7.2kw running. That would be a great choice RickF.

What about leaving the gen head connected to the engine block but removing ALL the unnecessary parts of the engine and using a pulley on the flywheel side of the crank to drive it? I might be a redneck!

I guess that sideload bearing stress is the weak link for belt driven generators. So 7Kw running seems to be about the limit. I was guessing that when I was looking at belt driven gens on eBay. I'll take another look at direct coupling a unit, Direction it needs to turn might become a factor in its mounting. Thanks John and Bob for the info. It looks like hurricane season is about to start. Every time I get these ideas, it's because I trake another look at that tractor and say " It's a shame to only use it for towing", So I buy a deck, then a snowplow, And say "It's a shame to only use it for those things", and the escalation continues.

3a8082e126