P8M4108a OTR a/c question

chessie4905 · June 13, 2018, 07:17:22 PM

The A-6 uses metal to metal clutch engagement, with no clutch lining involved.
Richard, If Luke changed front seal, he had to remove pulley and clutch. He should be able to swap pulleys.
The replacement compressor you listed is metric threads. Luke will have to substitute metric bolts for the us or sae. ones.
The replacment compressor has that oil so it can use r-134, according to the specs. Good time to switch over.

richard5933 · June 13, 2018, 07:29:05 PM

I appreciate all the comments on this thread about the a/c problems. We've made a few decisions and have ordered the compressor. It is going to be a bolt-in job with the two exceptions I wrote about earlier...The clutch is 6" dia instead of 5.5", and the oil is PAG instead of mineral oil.

The tech at the shop (and the tech at the compressor place) don't think that changing the oil to mineral oil will be a problem, but it might take a few fill and drain cycles to get it done. They are going to change the oil in the compressor before it's installed to avoid getting the oil in the system contaminated.

The clutch/pulley dia will likely not be a problem, assuming that there is enough adjustment in the mount to put the belt on and/or a larger belt can be found. There is a slight possibility that the smaller clutch/pulley and slower spin speed could result in insufficient cooling, but the tech at the shop doesn't feel it will be a problem except possibly at very slow-speed driving. If it is a problem, we could always swap our current clutch for the new one.

The shop is aware of the change to metric mounting bolts - I'm going to have to assume that they can manage that. If not, we have bigger problems.

We opted to not change refrigerant at this time, for a couple of reasons. The main one was that there was no real way to be certain that it would have adequate capacity to keep the bus cool after the switch, especially since our bus just has the one compressor and not the dual compressor option. There was also a question about how the rest of the system would perform with another refrigerant. The tech at the shop says that over the next year new formulations should be coming online that can be used to better replace the r22 that's in there currently. The r143 is used to replace r12, but it has much less cooling ability than the r22, or so I'm told. Either way, if we decide to switch it won't be that much more difficult later on than doing it now, we'll just have to switch oil again.

That's all I know right now. As things arrive to the shop and get installed I'll update. Hopefully someone else can learn from all this.

Everyone keep thinking happy cool bus thoughts...

luvrbus · June 13, 2018, 07:51:31 PM

I don't think the pulley will make that much difference AC compressors run 1:1 to !:4 of the engine speed last I heard

chessie4905 · June 14, 2018, 03:41:02 AM

I doubt it also.

richard5933 · June 21, 2018, 04:15:24 PM

Update...

After a long series of problems locating the compressor, shipping issues, rain delays, and scheduling issues at the shop we are finally making progress on this. Only two parts were needed - a compressor and a drier.

The compressor has been installed. There was more than enough play in the bracket to allow the existing belt to be used. The new drier was installed, and the compressor has been connected to the hoses. That's all good news.

When I stopped in at the shop at noon the mechanic was getting ready to charge the system with nitrogen/dye to test the system. I just checked with the second shift service writer this evening, and he says that the notes indicate things are still underway and moving along. Since the mechanic doesn't work Fridays, I guess that it will be Monday till I know more. Not sure if there were additional leaks or problems identified after I left the shop. Hope not.

The waiting and waiting is really starting to get to me. Always seems to be that something like this will happen right at the time of the year I want to be on the road.

eagle19952 · June 21, 2018, 04:51:13 PM

Quote from: richard5933 on June 21, 2018, 04:15:24 PM
Update...

The waiting and waiting is really starting to get to me.

the wait is worth it when the job is done right

richard5933 · June 21, 2018, 06:41:33 PM

Quote from: eagle19952 on June 21, 2018, 04:51:13 PM
the wait is worth it when the job is done right

Very true!

And sometimes you get a pleasant surprise, like the phone call I just got from the 2nd shift service writer. Apparently the tech is coming in tomorrow to try and finish the job for us this week, even though it's normally a day off for him. Sounds like the hangup today was just how long it's taking for them to properly evacuate the system, do a final leak check, and then refill with the r22. The guys at Lakeside International in Milwaukee are definitely going above and beyond.

After hearing the problems that bus nuts in other parts of the country have finding people to work on their buses, I am really luck to now have two quality shops where I can take the bus.

luvrbus · June 21, 2018, 07:18:21 PM

I would almost bet that system has a orifice hidden some place that will need replacing

richard5933 · June 22, 2018, 03:42:05 AM

Quote from: luvrbus on June 21, 2018, 07:18:21 PM
I would almost bet that system has a orifice hidden some place that will need replacing

Orifice? Are you generically describing a part or is there actually a part in the system called that? The tech working on the bus has the GM manual and years of experience, so I'm hoping that it's not so hidden he is unable to find it.

chessie4905 · June 22, 2018, 04:24:43 AM

That system uses an expansion valve to control the flow of refrigerant. The orifice type system didn't get used on the GM's. They were used in the cars in the late 70's onward, but GM didn't update the system on the coaches. Probably because sales didn't justify the expense of the change.

luvrbus · June 22, 2018, 05:53:35 AM

That is good to know the 5 buck orifice tube can cause a lot of head aches and so can a expansion valve

chessie4905 · June 22, 2018, 05:57:42 AM

Here's one you can use, at least, in cars for better performance.

http://www.acsource.com/smartvov-highperformanceorificetubes.aspx

Those tubes in the cars would plug up when the compressor started going bad and shedding aluminum and teflon debris. People didn't replace them after changing out compressor and couldn't get sufficient cooling because it was partially of fully plugged. That fine screen won't pass small particles

richard5933 · June 22, 2018, 06:37:34 AM

The system held vacuum overnight. Seems like we're finally heading in the right direction.

Oonrahnjay · June 22, 2018, 08:53:17 AM

Quote from: chessie4905 on June 22, 2018, 05:57:42 AMHere's one you can use, at least, in cars for better performance.

http://www.acsource.com/smartvov-highperformanceorificetubes.aspx

Those tubes in the cars would plug up when the compressor started going bad and shedding aluminum and teflon debris. People didn't replace them after changing out compressor and couldn't get sufficient cooling because it was partially of fully plugged. That fine screen won't pass small particles

I don't know about 4108 buses, but this sounds just like what I need on my 16-year-old TDI. Unfortunately, my VW guy tells me that it will run me over $1000 in labor alone to pull the dash and get into the A/C system.

eagle19952 · June 22, 2018, 10:58:41 AM

Quote from: chessie4905 on June 22, 2018, 05:57:42 AM
Here's one you can use, at least, in cars for better performance.

http://www.acsource.com/smartvov-highperformanceorificetubes.aspx

Those tubes in the cars would plug up when the compressor started going bad and shedding aluminum and teflon debris. People didn't replace them after changing out compressor and couldn't get sufficient cooling because it was partially of fully plugged. That fine screen won't pass small particles

Huh...a good shop shows you that, makes you feel all warm and fuzzy, that they know what they're doing...