News:

The ORG - Truly Independent and Unbiased!

Main Menu

A/C setback

Started by oscar, 31 October 2007, 12:32 AM

oscar

Guys, quick questions

To get access to the end of the hose that's thru the firewall, what do I need to remove?  Under dash knee pad or centre console or something else?  Does it go to the expansion valve or the exchanger box?
1973 350SE, my first & fave

koan

Quote from: Patrick Bateman on 31 October 2007, 06:40 AM

Indeed - if its leaking from between the end plate and the cylindrical housing, then yep, you just need to replace the O-ring. Personally I would replace the set if your going to the hassle of removing the compressor.


It is a bit of job to get the compressor off but in this case I'll just fix what's leaking and leave the rest alone, it is only a three years old replacement/rebuild.

Thanks for the tips on the sealing surfaces.

How well did your compressor fit the bracket?

koan
Boogity, Boogity, Boogity, Amen!

koan

Quote from: oscar on 31 October 2007, 04:54 PM

To get access to the end of the hose that's thru the firewall, what do I need to remove?  Under dash knee pad or centre console or something else?  Does it go to the expansion valve or the exchanger box?


It goes to the expansion valve which can be replaced through the instrument cluster (with a fair bit of perseverance).

If you can get the cluster out from the front the rest can stay in place.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

Quote from: koan on 31 October 2007, 06:14 PM
Quote from: Patrick Bateman on 31 October 2007, 06:40 AM

Indeed - if its leaking from between the end plate and the cylindrical housing, then yep, you just need to replace the O-ring. Personally I would replace the set if your going to the hassle of removing the compressor.


It is a bit of job to get the compressor off but in this case I'll just fix what's leaking and leave the rest alone, it is only a three years old replacement/rebuild.

Thanks for the tips on the sealing surfaces.

How well did your compressor fit the bracket?

koan


it fit the bracket the first time.

to reinstall the compressor with the engine in place wasnt all that hard either, you can drop it in after you remove the battery and battery tray, so removal would be thru the same area.

As for unbolting/rebolting in it etc, I dont remember how hard that was, it dosent stick in mind so it cant of been that difficult.

oscar

Quote from: koan on 31 October 2007, 06:23 PM

It goes to the expansion valve which can be replaced through the instrument cluster (with a fair bit of perseverance).

If you can get the cluster out from the front the rest can stay in place.

koan


Cheers, koan.  Spot on especially about perseverance.  Mixed results today.  I got cold air for the first time today.  I used the hose from the yellow motorless 280.  The problem is I yanked too hard to get it and the grommet through the firewall :-[ so I got leaks and had to bleed the system again.  I'll try turd 280 hose with a little more care tomorrow. 

Whilst my gauges were showing correct pressures - 30psi and 160psi as per the Hychill manual - the air was cold but not freezing like yours is Pat.  I found the leak just before a test drive and just before I got a chance to do a vent temp reading.  What should I expect?

Check the pic of the old hose :o,
2nd pic is the replacement hose with a much longer sheath that was missing from the original on the 350.
3rd pic is the leaks near the firewall :(  Definitely caused by my heavy handedness whilst recovering it.



1973 350SE, my first & fave

Big_Richard

Oscar!  :o

Shame on you  :o

Never before have i seen such butchery.

Calm down, I know your excited, but Slow and steady wins the race, you cant rush these things ;)

Big_Richard

Ps, my refilling style utilised the "she'll be right" method, IE, no guages.

I will get the gauges onto it, and see what its really doing.

I'm still pulling zero celcius vent temperatures, the once a month that i start the car.

koan

Quote from: Patrick Bateman on 01 November 2007, 02:58 AM

it fit the bracket the first time.

to reinstall the compressor with the engine in place wasnt all that hard either, you can drop it in after you remove the battery and battery tray, so removal would be thru the same area.

As for unbolting/rebolting in it etc, I dont remember how hard that was, it dosent stick in mind so it cant of been that difficult.


Mine fits the bracket but when the front bolts are done up, one of the bolts at the back (the only one? can't recall) tends to pull the compressor end plate off, I filed down a washer as a spacer and used it to fill the gap. I was concerned the rear bolt would pull the end plate off leading to a leak - which is what I have now.

Your car must be different! It's the biggest pain in arse to get on and off, inaccessible bolts, especially that one into the side of the block, no room to swing a spanner.

I put mine in from the bottom, I wouldn't have thought it possible from the top, this time I'll have the dry sump hoses off for re-hosing as they are starting to seep at the ends so it might be a bit easier.

koan.
Boogity, Boogity, Boogity, Amen!

oscar

#23
Well, it's working.  I was so pissed at screwing up that 2nd black hose that at midnight last night I went and grabbed the turd 280's hose and transplanted it into the 350.  Put a small charge in it overnight then topped it up this morning.  I'm stoked it's working but at the same time, wondering if it's cold enough.

Second test drive not long ago - Vent temp was 14 at it's lowest but usually sat around 16-17degC.  That was at 2000rpm, around 80km/hr and switched on recycle and full fan speed.  Negligible difference at idle and a tad cooler at 100km/hr and getting up to around 3000rpm.  Outside temp was 30degC.  Inside temp of the car was 56degC at first and took around 1-2mins to cool right down and make the driver comfortable and happy.  Suction hose is very cold, high hose is very hot. 

I'm not sure now if I've put enough in but I don't want to put too much in.  What should I see in the receiver/dryer window?  Whilst filling it looked like a front end loader washing machine.  Now it looks full, but no action, no bubbles.  Another forum said this Hychill stuff would always froth.   I don't know.  What do you see Koan?  I shall see how it goes for a couple of weeks.  No BBQ gas smell and soapy water test passed, the only leak is from the low pressure schrader valve.  Tiny, tiny leak, hopefully controlled by the cap.

EDIT: oops, posted without a pic ;D  FWIW, this the 3rd hose from the turd 280.  Being a 77 model I noticed the hose was blue, not black like the other two pre 76 models.  Better nic than the other two it had similar markings, was the same length and fortunately, had the same fittings. Also had 23Bar stamped on it but the markings on the other two hoses are illegible.

1973 350SE, my first & fave

koan

#24
EDITED after rereading oscars post.

From what I've read about the Hychill gas if the sight gas liquid is bubble free you have more than enough. I put a 300 gm can in at first and there was froth, like bubbles in the sink. I put an arbitrary amount more in, probably about 100 gms (correct charge is 330 gm) and it was pretty much as you described - like a front loader.

You probably have too much in there, if the very cold return hose has frost on it you definitely have too much gas. You could be flooding the evaporator with liquid meaning that part of the evaporator is effectively not there or run the risk of having fluid in the return line entering the compressor which is not too good at all. 

koan
Boogity, Boogity, Boogity, Amen!

oscar

Hi koan, I found this extract from charging tips.

With Mercedes cars, a high pressure cut in switch turns the electric fan on when the air conditioner system high pressure reaches 280psi.  This is too high for HR12 to be efficient.  With these models, you should fit a Bosch mini relay to activate the condenser fan whenever the compressor clutch is engaged.

There are far too many variations on Mercedes systems to document, those that will not work on HR12 have one problem only - it is impossible to obtain enough airflow through the condensor to make a reduction in refrigerant temperature in the condenser.

As HR12 rejects heat into the condenser 50% faster than R12/R134a, the heat of the refrigerant can be higher than the TX valve will tolerate, resulting in poor evaporator performance.


Now, obviously our systems work with HR12, but I think I might benefit from installing an aux fan.
1973 350SE, my first & fave

Big_Richard

#26
Today - I took some measuresments - (temperature)

fan position 3, recirculated mode, coldness knob turned all the way to full cold.

vent temperature 2 celicus before compressor cycles.
condensor input 45 celclius while running. (irrelevent, ambient temperature is only 25)
condensor output 30 celcius while running. (will be more interesting on a hot day)

I've never been able to have the vents directed towards my face as the arctic breeze makes my nose run and dryes out my eyes.

koan

Quote from: oscar on 02 November 2007, 08:20 PM
Hi koan, I found this extract from charging tips.

With Mercedes cars, a high pressure cut in switch turns the electric fan on when the air conditioner system high pressure reaches 280psi.


Our vintage vehicles vehicles don't have that, they have a low pressure cutout to protect the compressor and a high refrigerant temp switch to turn on the aux fan - if you have one.

Don't think there's a problem with the expansion valve, I've had my old one apart and there' nothing to melt.

I think there was an aux fan on ebay when I looked a couple of days ago, but just drive it and see what how it is.

BTW, zero vent temperatures are not good as the condensation on the evaporator is going to freeze and prevent airflow.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

Quote from: koan on 02 November 2007, 09:55 PM


BTW, zero vent temperatures are not good as the condensation on the evaporator is going to freeze and prevent airflow.

koan


There is an anti icing switch on the evapourator, this is not possible - when it reaches 0 celcius the compressor is switched off imediatly, either by this switch, or by the thermostat.

koan

Quote from: Patrick Bateman on 02 November 2007, 10:06 PM

There is an anti icing switch on the evapourator, this is not possible - when it reaches 0 celcius the compressor is switched off imediatly, either by this switch, or by the thermostat.


Climate control models have a 2 degree C ETR switch (Evaporator Temperature regulator) to the prevent icing but to the best of my knowledge the standard "two knob" models don't, mine certainly doesn't.

Maybe someone who has had the heat-A/C box stripped to its fundamentals could correct me if I'm mistaken.

koan
Boogity, Boogity, Boogity, Amen!