Clarification on AC charging/troubleshooting - PeachParts Mercedes-Benz Forum

Douge · #1 05-25-2009, 07:19 PM

I need to get my ac going better in my 86 420sel, car has 133k with good service history and very clean. This is my daily and the AC is now far below acceptable. I have done some fooling around based on searching but here is what I have.

I can hear the compressor kicking on, it is making some noise, more noise that normal I should say which leads me to think low oil/freon. The out line is cool but not cold cold like a properly operating line would be.

I have some R12 and my knee jerk is to just add some refrigerant but there must be some prob right.

I mean it is a mercedes. So if I do just add some refrigerant which is what I want to do, how do I get the lube oil in? I only have two cans of R12 so I don't want to waste it.

I guess I am debating the bandaid v. emptying it out, cleaning the lines and replacing the exp valve and drier and paying someone to do a vac test and recharge. I know you guys will tell me to do it right, but can I get the cheat code as well?

Thanks.

Doug

jwhughes3 · #2 05-25-2009, 07:54 PM

You can buy a 2oz oil charge at O'Reilly's or AZ - If it is still cooling somewhat then just recharge it but use a set of gauges to be sure it is correct.

John in San Antonio

Matt L · #3 05-25-2009, 09:55 PM

Do not buy oil from O'Rielley's to add to your car, if you're running R12. They do not sell the appropriate oil. And don't ever add oil unless you think you need it. Too much oil is bad in a number of ways.

So there is still positive pressure in the system? How long has it been since it was serviced? A very small loss per year is acceptable, and almost unavoidable. Perhaps recharging it is actually in order.

Arthur Dalton · #4 05-25-2009, 10:40 PM

The car still has pressure b/c the comp is coming on..so, watch the eyesight to clear as you add ..if you have comp activation and steady foam in the eyesight, it will usually require only 1 can or less.
Gauges are better, but with R12, the eyesight is an accurate charge inducator..look for aux fan activation as you near capacity.

Douge · #5 05-25-2009, 11:38 PM

Thanks guys, I now have a secondary prob. I think my HVAC controller bit it as well. I can no longer turn it off!

Were havin fun now!

So you think that a top off of freon is OK? In my searches I saw a couple of posts that clearly said to address oiling when adding freon. I know some of the new 134 has oil in it, but the R12 does not.

Douge · #6 05-26-2009, 06:11 PM

Pretty sure its my hvac control unit. I have been leaving the wheel at min and getting next to nothing. When I finally got tired of the non existent cooling yesterday I was fooling around with it and found out that the even with the system off, the fan is still turning at low speed. Today, with the wheel left in what is normally a good setting for me, the AC decided to make some ice cubes.

So I think my ECU has a short yes? The detente at the minimum position appears to actually turn the AC off rather than on, and with the fan staying on in the off position, I think that suggests something amiss.

Lastly, still think the compressor is making a bit of noise and going to have that checked. Check the pressure and see if I can figure out if needs some more oil/Freon.

Matt L · #7 05-26-2009, 08:52 PM

You need oil if you have a catastrophic refrigerant loss, such as you get when a hose blows off its fitting. That will blow liquid refrigerant out at a very high rate, and it will be carrying a lot of oil.

Slow leaks normally do not require oil to be added. For my 96, oil is specified to be added for slow leaks only if the system is at least 400g low. I don't recall the quantity, but it's sure to be different figures for your car anyway.

Oil is also added when changing parts, since the oil collects in the low spots when the system is idle.

mbbuff · #8 05-26-2009, 10:27 PM

Do you think you may have an unacceptable leak in the system? If so, you may want to add some leak check dye to verify before you use up your precious R12. As said above some slight leakage over time is OK. Adding oil or discharging the system would be a last resort only if you're sure there is a problem warranting it. If you can find someone that can service with "Freeze 12" (totally compatible with R12), that would also be another option, IMO.

Arthur Dalton · #9 05-26-2009, 10:30 PM

Put a gage on it or look at the sight glass..then you know where you stand..

hk20000 · #10 05-26-2009, 10:31 PM

in Canada they are selling this R12A product to public, it comes with its own gauge and lube and stuff. The package says it "meets or exceeds factory requirement of vehicles operating with R12 refrigerant". I used a bit of that and it worked perfect for me.

http://www.redtek.com/products_refr.html#

Since R12 is completely banned from Canada, this turned out to be very viable stuff. It's also freon-free so you tree huggers don't have to worry about a thing. Kit comes with a pressure gauge.

tinypanzer · #11 05-26-2009, 11:04 PM

Yes, but it is likely to be HIGHLY flammable.

Douge · #12 05-26-2009, 11:11 PM

Quote:

Originally Posted by Arthur Dalton

Put a gage on it or look at the sight glass..then you know where you stand..

There is a steady unbroken stream of milky anitifreeze colored goo in the sight glass and the compressor is rattling. The compressor is def. rattling.

It is working though. I can hear all the vac actuators huffin and puffin back there as well.

ds190 · #13 05-27-2009, 04:17 PM

Quote:

Originally Posted by mbbuff

If you can find someone that can service with "Freeze 12" (totally compatible with R12)

FYI, Freeze12 is 70-90% r134 and 10-25% chloro-diflourethane, according to their MSDS.

It is difficult for me to understand how it is totally compatible with r12.

Arthur Dalton · #14 05-27-2009, 04:21 PM

Quote:

Originally Posted by Douge

There is a steady unbroken stream of milky anitifreeze colored goo in the sight glass and the compressor is rattling. The compressor is def. rattling.

It is working though. I can hear all the vac actuators huffin and puffin back there as well.

Charge it ...