82 240D AC No High Side Pressure - PeachParts Mercedes-Benz Forum

300d 4 ME · #1 07-14-2016, 10:49 PM

I dabbled in the AC on this tan slug recently.
Pulled a vacuum, it held it well. Added 3 cans of r134a (36OZ). The compressor clicked on, now makes a clunking, pop bottle crushing sound. I know thats with the clutch, not bothered at the moment about it.

Anyway, It had like 50 psi on the low, and NADA on the high. Now I know "That ain't right"

. Yes my gauges work!

The air coming out the vents is Meh at best.

I checked the High side port, even removed the tire valve, nothing came out...... Low side still has pressure.

So there is a clog somewhere. But where? Did the compressor just die?

The PO in the last 10 years spent several thousand $'s on the AC.

Still doesn't work!

This car has manual climate control. So thats something good.

leathermang · #2 07-14-2016, 10:54 PM

There is a good thread in my signature on AC...
we do not recommend pulling vacuum as the definitive leak test...

300d 4 ME · #3 07-14-2016, 10:59 PM

Thanks for that. The no high side pressure has me baffled... I'm not an expert on this subject!

jack.stew48 · #4 07-14-2016, 11:45 PM

stuck expansion valve? like 100% stuck?

also not an expert but know the basics of the system this might be a possibility

leathermang · #5 07-14-2016, 11:59 PM

If the Txvalve were completly stuck closed it would be the low side which had no pressure... high side is from compressor through condensor through receiver dryer... up to the Txvalve...

vstech · #6 07-15-2016, 07:40 AM

Well... What is between the compressor and the service port? Nothing... The line exits the manifold, wraps under the engine and sits by the alternator, then into the condenser, then into the receiver, then into the TXV...

If you have no refrigerant in the high side... Only possibility is you dumped the cans into the suction side, destroyed the compressor, and the TXV is plugged... Sorry

funola · #7 07-15-2016, 09:09 AM

Was no pressure on hi side with the compressor engaged/engine running? What about with engine off? Static pressure of 134a in the summer should be a a few psi higher than ambient temp in F and should be the same on both the hi and low side.

vstech · #8 07-15-2016, 11:57 AM

I cant wait to hear what this is...

leathermang · #9 07-15-2016, 12:29 PM

Quote:

Originally Posted by vstech

I cant wait to hear what this is...

LOL

300d 4 ME · #10 07-15-2016, 12:34 PM

Running or not, the high side pressure is 0.

It was converted to r134A at the dealer years ago. Has the MB sticker saying that.

I filled it from the low pressure fitting, above the radiator. The high was connected under the exhaust manifold.

You can see refrigerant in the sight glass, on the dryer.

Since thousands were poured into the AC on this before me. I bet the compressor was shot long ago. From others not knowing what to do.

The PO said there was something screwy with the AC anyway.

Wouldn't elaborate on what....

At least I am doing this on a old 240d.

I may wait a little until cracking into the Citroen CX AC right beside it..

ah-kay · #11 07-15-2016, 12:47 PM

Quote:

Originally Posted by 300d 4 ME

I dabbled in the AC on this tan slug recently.
Pulled a vacuum, it held it well. Added 3 cans of r134a (36OZ).

You overfilled it. R134a should be 3/4 of of R12 volume. w123 specifies 2.2lb ( 35.2oz ) of R12. 26.4oz of R134a is enough. Compressor may be very noisy if overfilled. It is also possible the compressor is seized or you don't measure it right. It is next to impossible to have 0 pressure on the high side. If anything is blocked then the pressure should be even higher.

BillGrissom · #12 07-18-2016, 03:07 PM

Post #7 is right on. With engine off, if you have 50 psig at low-side port, you should eventually measure 50 psig on the high-side port also. The compressor flap valves do not make a perfect seal and the expansion valve is a metal-metal seat (I think), so should leak somewhat. You removed the high-side Shraeder valve, so would have to be real big gunk to clog the port.

I would start taking tubes apart and blowing them clean. Change O-rings while doing this. But, remember that venting any refrigerant to the atmosphere is illegal and the EPA may have drones watching.

If it sat without pressure for long w/ R-134A oil, it may have absorbed moisture, which forms corrosive acids. Not as much a problem w/ R-12's mineral oil. Look at PAO 68 oil, since no such issue and works w/ all. If you continue w/ R-134A, be aware it is disappearing.

leathermang · #13 07-18-2016, 03:13 PM

I am wondering if this is a measuring error...
not with your gauges..
but perhaps with that ' tire valve 'as you call it....
you said nothing came out... perhaps it does not actually connect to the high side and that is what is giving you that zero reading.... as what others have said is true.. both that you seem to have over filled it... and that it should read the same on both sides after sitting....

vstech · #14 07-18-2016, 05:29 PM

I'm thinking it's an adapter issue as well...

when it was converted, an adapter was threaded onto the R12 port. taking out the "tire valve" in the adapter would not release the pressure, there is another valve in the R12 port under it.

you might want to try heating the adapter, and unscrewing it... I say heating it, because most are attached with loctite to prevent removal... and well let's just say I've had them rip the R12 fitting off the line before... read my quote in my sig... that happened...

300d 4 ME · #15 07-18-2016, 08:57 PM

That high side valve is directly open to the junction of the line(L shaped end of hose). I can see straight down it.

The reason I kept going was, it was a new set of gauges. From Harbor freight no less!

After this car, I popped them on another, the gauges work perfect...

I don't know if I killed the compressor, but it surely didn't help over filling it.

Me, and the last 2 owners have not had working AC(6+ years?). Before that many thousands of dollars were funneled into the AC, by a MB Dealer.

I have the receipts, it had a new compressor in the early 2000's. Not that it matters now, just saying.

Now that I know what to look for, I'll get to it in time. Or Winter will hit , and I can save the trouble!