Getting ready to get the AC working - PeachParts Mercedes-Benz Forum

funola · #1 07-21-2010, 05:39 PM

I made one "good" R4 compressor from 2 that I have. Before I install it, I wanted to set up a "bench" test so I do't waste more of my time if it's no good from the get go.

The battery charger is to engage the clutch. I have a compression gauge shoved into the pressure side of the R4. I put in 2 oz of mineral oil and swashed it around. The motor is 1/2 HP and the motor is mounted to the plank of wood but the R4 is tensioned by hand. It definitely puts out pressure but I couldn't measure how much because the motor does not have enough torque. The compression gauge blows off when the R4 is spinning but if I push it in to stop it from blowing off the motor can't keep up and stalls. Anyone know how many HP the R4 needs? Anyway. I tried and will not go any further with the test like getting a bigger motor and mounting the R4 with an adjustable tensioner bracket.
I have a good feeling this R4 will be OK so will install it when I have time, check the system for leaks and if none, flush, evacute and charge with Envirosafe ES12A unless I come upon some R12 real soon.

Yak · #2 07-21-2010, 06:55 PM

If you put that electric motor into your car, could you have a battery powered A/C, so it didn't rob your horsepower? Like a hybrid? Genius!

If you need HP, can't you you hook it up to a lawnmower engine?

That is some definite out of the box bench-test thinking.

funola · #3 07-21-2010, 07:48 PM

A lot of things can be done given enough time/money/desire! Did you put your Compressor Works R4 in yet? What refrigerant will you be using? Do you have a thread going?

Yak · #4 07-21-2010, 08:00 PM

No. And I'm bummed.

I'm doing a full up, new parallel flow condenser install and I'm waiting for a new custom hose. "The fitting's on back order...it'll ship tomorrow..." so they said two weeks ago.

I'll be going 134a, since I can't find R12 easily in San Antonio and I don't want to mess with the diminishing supply problem. The one ad I've seen on CL didn't pan out, Carlisle's off of SW Military (just to pre-empt commentary from the Alamo City crowd) said they wouldn't do R12, but they would build me custom 134 hoses, and I just don't feel like swimming against the tide. I've got too many other things to worry about than getting certified to work on my car.

I've got my new O-rings, receiver dryer, one new hose, expansion valve, system flushed and a new compressor all ready to go. I just need a darn #8 female to #10 O-ring insert 90 degree fitting.

Two hoses and a new PFC that 'should' fit into a 123 are only $140, for those who are interested in getting a few more degrees of cooling from your 134 in a W123. Pics and data will be posted when I get the parts.

funola · #5 07-22-2010, 09:45 AM

Good luck with your install. There was a post a few years ago with a parallel flow condenser install with R134 that did not get very cold. I think it was on an SD. I'll see if I can dig up the link.

There's one more test I will do which is a pressure test to check that I have no leaks. I was gonna change the seals but that would mean more delay and potential for more to go wrong. If there's no leak it's going in as is.

funola · #6 07-22-2010, 11:42 AM

Here's a good discussion on flush solvents

http://www.autoacforum.com/messageview.cfm?catid=2&threadid=19751

funola · #7 07-22-2010, 07:59 PM

Pressure tested the compressor. Pretty crude setup but it works. I used two half hoses plugged the ends. Connected the manifold gauge to the shrader valve and pressurized with bicycle pump and used soapy water. Seems to be holding pressure. I couldnot put soapy water at the main seal since it's hidden by the clutch. No leaks anywhere else on the compressor. It's going in!

Gene Horr · #8 07-22-2010, 10:05 PM

Isn't the compressor a positive displacement design? If so it will always stall if you don't have fluid/gas flow.

As to HP a _real_ 1 hp motor should be fine for a test. Just remember that with a motor is made in China (and some other overseas sources) any relationship between the advertised power and reality doesn't exist.

turbobenz · #9 07-23-2010, 04:00 AM

judging by how much power is sucked from the motor you may need like 2-3 hp at least to turn that thing if its putting out 250-300psi at the high side. If i were you id take it to an ac show and see if they can bench test it for like 20 bucks or something

vstech · #10 07-23-2010, 08:41 AM

you are going to need 3 or more HP. REAL HP, not max HP either. industrial motor only... that little 1725 1/3HP ain't gonna cut it.
and he's got the suction line open for the pressure test, so he's compressing air. if he plugged the suction line, it would draw vacuum, and he could test that to see how tight the valves are.

funola · #11 07-23-2010, 08:57 AM

Quote:

Originally Posted by vstech

you are going to need 3 or more HP. REAL HP, not max HP either. industrial motor only... that little 1725 1/3HP ain't gonna cut it.
and he's got the suction line open for the pressure test, so he's compressing air. if he plugged the suction line, it would draw vacuum, and he could test that to see how tight the valves are.

Yeah I shoulda put a vacuum gauge on the suction port and done a vac test also. I ran out of time and had to stop. Vac and pressure in a compressor is related no? E.g. you can't have bad vacuum and good pressure.

funola · #12 07-23-2010, 09:00 AM

I will have a quart of Dura II flush solvent and a quart of mineral oil Monday. Plan is to install the R4 , hook up the lines and check system for leaks. If no leaks, then flush, replace dryer and evac and charge.

vstech · #13 07-23-2010, 10:41 AM

I'd flush first, then replace all orings and then test for leaks.

funola · #14 07-23-2010, 11:56 AM

Quote:

Originally Posted by vstech

I'd flush first, then replace all orings and then test for leaks.

Tell me if this makes sense. I have not checked the rest of the AC components for leaks. Checking the compressor on the bench (actually on the ground) has been a bit of work to set up. I figured since it was out already, why not test to see if it is OK before re-install.

If I flush first and find that I have a leaky condenser or evaporator. I have wasted expensive flush solvent ($34/ qt) on them. That's why I want to check system for leaks first before flush. Is my logic correct?

funola · #15 07-23-2010, 12:02 PM

I rented the clutch plate puller from Autozone again so I can soap bubble test the main shaft seal. No bubbles! It's going in!

Should there be a cap on the center bolt to keep the threads from rusting out?