A/C Pressure Check Question - PeachParts Mercedes-Benz Forum

Graplr · #1 03-26-2008, 05:42 PM

After making it through last summer without A/C, I decided this winter I would look into my system come spring.

I bought this manifold set http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92649 from Harbor Frieght.

My car has a sticker on it saying it was converted to R134a in 2001.

I just went and tried to hook the gauges up and the connections would not fit.... I attached a pic of the RED High Side connector from my car so that hopefully someone could tell me if this truly is a R134a connection or if it is still the old R12 connection.

My question...why won't my gauges fit onto the connection? Do I need to buy some sort of converter?

Thanks! I'm sure I'll have tons more questions once I get the darn thing hooked up!
-Ryan

leathermang · #2 03-26-2008, 07:50 PM

I think it is the R134 connector... perhaps they sold you the R12 guages ? or left out the fittings they list in the ad ?

engatwork · #3 03-26-2008, 08:33 PM

That is an r134 fitting. Your gauge set connector should fit onto it without issues.

JimmyL · #4 03-26-2008, 08:42 PM

I bought a set of the Harbor Freight gauges and the high side wouldn't fit. I returned them, exchanged them for a different set, and the low side wouldn't fit. I returned them for a refund [they asked it I wanted to try another set

]. Only bad thing I have ever gotten from them, but it sounds like they have serious issues with their supplier of those

vstech · #5 03-26-2008, 09:35 PM

the best set by far is from autozone it is a universal set with R12 hoses and 134 adapters that screw into the hoses... think of the possibilities... about 70.00 IIRC... WELL worth it, but DO NOT DROP THE MANIFOLD... the gauges are cast brass, and they break off at the manifold... very hard to remedy.

Graplr · #6 03-26-2008, 09:38 PM

Thanks for the replies....

The connect from the gauges is literally a screw on. It looks like to me that they are for a different attachment.

I added a pic with the gauge connection next to the red high side on the car. They don't even come close to fitting. Makes me think it is the wrong hose attachment??

I bought them 2 months ago online when I ordered something else. There is a 90 day Guarantee Certificate in the case. I'll bring it into the store and see what they say.

engatwork · #7 03-27-2008, 06:21 AM

I was referring to the hi side connector shown in pic of your link as being the correct one. I did not realize that you only had the screw on fitting. Something is not riot right with your kit.

JimFreeh · #8 03-27-2008, 07:27 AM

R-12 can be identified by threads on the outside of the port. High and low sides are different diameters, the high side being larger. Hoses are usually color coded blue for low, and red for high.

R-134A ports are of a "quick disconnect" style, similar in function to a air compressor connection. High side is also larger diameter than the low side. Hose connections have a valve at the disconnect point. It's a rising stem valve, screw out to close, in to open. As with R-12 manifolds, blue is low, red is high.

R-12 and R134A also have different fittings on the hose connections to the manifold. R-12 is 1/4 inch flare, not sure what R-134A spec is...

Jim

Graplr · #9 03-27-2008, 09:44 AM

Quote:

Originally Posted by engatwork

I was referring to the hi side connector shown in pic of your link as being the correct one. I did not realize that you only had the screw on fitting. Something is not riot right with your kit.

Yes, you answered my question of the R134a or R12 fittings on the car. Thank you.

My next question is/was my supposed R134a gauges don't fit on them. (as you can hardly see in the dark pic!

) It doesn't appear to be a 'quick-connect' fitting on the hose gauges, it appears to be a screw on. They don't even come close to fitting. So that would lead me to believe I need an adapter, but JimmyL says he ran into the same problem with the same gauges. My plan is to take them to Harbor Freight and see if they will exchange them or if they do need adapters.

Graplr · #10 03-27-2008, 09:45 AM

Quote:

Originally Posted by JimFreeh

R-12 can be identified by threads on the outside of the port. High and low sides are different diameters, the high side being larger. Hoses are usually color coded blue for low, and red for high.

R-134A ports are of a "quick disconnect" style, similar in function to a air compressor connection. High side is also larger diameter than the low side. Hose connections have a valve at the disconnect point. It's a rising stem valve, screw out to close, in to open. As with R-12 manifolds, blue is low, red is high.

R-12 and R134A also have different fittings on the hose connections to the manifold. R-12 is 1/4 inch flare, not sure what R-134A spec is...

Jim

They appear to have a 'quick-connect' fitting with threads on the inside of the port. Is that how they are supposed to look for R134a?

JimmyL · #11 03-27-2008, 10:07 AM

This is the set I got from Harbor Freight.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92649

As you can see, on the right of the container are the two fittings that screw on to the hoses and then quick-connect to the R-134a fittings on your car. {or try to connect

}

**edit**
I think you have to make sure they are unscrewed all the way out, connect them and then screw that top piece in. Maybe that is your question. Even doing that mine wouldn't fit correctly. I even had a misplaced o-ring in one of the sets of the connector, so it actually had 2 problems.
Spend just a little more and get a better gauge set.

KarTek · #12 03-27-2008, 10:10 AM

The quick connect I have on my r-134 hose looks much like a small air hose fitting. it has a small sliding collar and balls inside the opening that engage the ring on the connector on the car.

Graplr · #13 03-27-2008, 11:29 AM

Quote:

Originally Posted by JimmyL

This is the set I got from Harbor Freight.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92649

As you can see, on the right of the container are the two fittings that screw on to the hoses and then quick-connect to the R-134a fittings on your car. {or try to connect

}

**edit**
I think you have to make sure they are unscrewed all the way out, connect them and then screw that top piece in. Maybe that is your question. Even doing that mine wouldn't fit correctly. I even had a misplaced o-ring in one of the sets of the connector, so it actually had 2 problems.
Spend just a little more and get a better gauge set.

I think we just found the problem...I have never used manifold gauges before so I was trying to figure out how to connect them. The link is the set I bought. I had the 'quick-connect' fittings on wrong. I had them connectted to the side of the gauges (connected by the quick connect) leaving the end that is supposed to be in the hoses to connect to the car...whoops!

Okay, I'll try it again tonight now that I know how the fit and report back!

Thanks for your help everyone!

leathermang · #14 03-27-2008, 12:20 PM

I am sure you are not the only person that has done that....

Graplr · #15 03-27-2008, 04:47 PM

Okay, I got the gauges hooked up. The blue low side went on rough but got it on after a little wiggling.

Ran the car and started it up, opened the valves. Let my car run on full cooling for a few minutes. Neither gauge moved. Both sat at 0. Pretty sure everything was hooked up correctly....this time.

Does my compressor need to be working in order to register pressure? Or is there another reason why nothing registered?

Thanks!