dr bob

I attach the vacuum pump to the schrader port that's underneath the pressure switch. Evacuate there, with the charge manifold attached to the usual places and the bottle attached to the center/yellow hose. Open the low-side valve to the gas cannister, but leave the valve on the cannister closed until you are ready to introduce gas. Evacuating this way insures that all the air is out of the system as well as the charge hoses and manifold.

I don't have the press/temp chart for R-134a with me to tell you if there's air in it from your static readings. Compare the press usre and your temp readings with the low-side gauge and see if they line up. It takes a lot of air to show up this way, only a little to affect the system performance, unfortunately.

I don't know your specific pump. If you bled out or recovered the old gas before attaching the pump, you won't see much if any vapor feezing as it comes out. You may be seeing oil carryover if the flow is too high. That should calm down as soon as you get a few inches of vacuum drawn. If you still see a lot of oil carryover, look for a valve marked 'gas ballast' and open it. That should cut the pump oil carryover a lot. Make sure there's still the right amount of oil in the pump at all times.

I'm a little out of position right now to give definitive AC answers.

Tampa 928s

This must be the rennlist version of home alone today

I have conflicting information on the amount of ounces in my 86.
One chart says pre-88 1050 grams which equate to 33.33 Oz after the 10% conversion. The other 850 grams which equate to 26.98 Oz after the 10% conversion. Also an article states you need to add an additional 2-Oz due to the R-134 remaining in hoses connected to the gages, any feedback?

Tampa 928s

What I found was my low side connector is leaking a little causing the vapor and when I closed the gage it leaked down to 0. When I used the high side only it pulled almost 30 and held when the valve is shutoff. These are new gages and hoses it must be the R-12 to R-134 adapter that is not sealing on the low side. So good news is no leak in the system but I need to address that adapter and figure out the capacity which I believe is 1050 grams but not sure about the two additional onces to make up for the gage hoses. Damm this is too precise for anyone.
Thanks Dr Bob

dr bob

Pull the old schraeder valves out of the R12 ports before you install the R-134a adapters. Use good adapters too.

Tampa 928s

I know we touched on this before but I need to make sure about this.

A found a replacement for R-134a it is freeze-12, site says it is not flammable; is this the same as the one mentioned: Louis Ott caught his car on fire using a hydrocarbon based refrigerant. Reading the site seems to me a good substitute any feedback.

http://autorefrigerants.com/co00030.htm

Tampa 928s

Another ? when I add the R-134 with the compressor OFF being pulled in by the vacuumed system I heard that you add it to the high side.
Any truth in this?

From internet post: About 35 years ago I ruined TWO REBUILT compressors in ONE DAY by putting Freon into the suction side as liquid. It froze and cracked the reed valves. AC people put LIQUID refrigerant into the HIGH SIDE of the system to avoid this. They may put it in without the compressor running... after the system has been at rest.... so as to install at averaged out pressure in the system.

JHowell37

I've never heard of adding R-134a into the high side. It's easy to avoid putting it in as a liquid. Don't turn the can upside down, and don't hold it above the manifold gauges.

dr bob

For the initial fill you may want to introduce the refrigerant as liquid, and at that point you want it to go into the high side first. This engine not running of course. That way the liquid flashes to vapor away from the cannister, using heat from the condenser and the drier instead of stealing it from the refrigerant, something that slows down the refrigerant flow pretty quickly. You MUST close the high-side valve before you start the engine. You MUST close the high-side valve before you start the engine. You MUST close the high-side valve before you start the engine. Repeat after me...

Tampa 928s

I purchased a freon scale and did the following:

I converted the 1050 grams to ounces and came out to 33.33 onces with the 10% off for R-12.
I vacuumed it down for several hours it went to -30 and it held overnight.
I filled it with R-134 the scale measured 2.10.30 Lbs when I was done, just a hair over the 2.083 recommended.

Ambient air 82 degrees
The static pressure when car was cold about 100 Lbs.
At idle:
Low pressure was 32
High was 250
At 3500 Rpm's
Low pressure was 20
High was 300

This seems high but I used the 1050 grams recommended in the manual for pre 89 the post 89 was 850 grams.
Could it be my information is not correct?

Tampa 928s

Morning forum: Anyone had a luck in finding the correct amount of R-134 for my 86 no rear air ?

From post on forum: All conditions effect the pressures. But on a 90 deg day, w/ hot engine, you should average 25 to 40 low, 195 to 250 high.

I read a few articles and that the best way is to measure outlet temp and balance it with the system pressure is by either adding or releasing a small amount of refrigerant. It seems I will wait until later today when the temp is high and check and bleed to achieve the correct pressure "what ever that is". If anyone wants to yell "stop" please chime in, everything was done the right way but I'm concerned about the high pressure. The more I read the more knowledge I gain and the more options, opinions and just pure seat of the pants attitudes I see, "does this sound like global warming" I find myself with information overload.

Back to basics:For an 86 no rear air at 90 Degrees at idle
Amount of charge ?
Low side pressure ?
High side pressure ?

Back to basics:For an 86 no rear air at 90 Degrees at 3000 Rpm's
Amount of charge
Low side pressure ?
High side pressure ?

Is it really that simple???

dprantl

You added too much R134A. The 1050g number is R12 for an '86 with no rear air. The 850g (or 860 I believe) number is a converted R134A number for an '86 with no rear air. When I did my '86 with no rear air I put in 33oz of R134A, which converts to 936g (about 11% less than the R12 value).

Dan
'91 928GT S/C

Tampa 928s

You added too much R134A. The 1050g number is R12 for an '86 with no rear air. The 850g (or 860 I believe) number is a converted R134A number for an '86 with no rear air. When I did my '86 with no rear air I put in 33oz of R134A, which converts to 936g (about 11% less than the R12 value).

Dan

I'm a little confused I put in 33.33 ounces or close to it based on the 1050 number minus the 10%. Is this not the same amount you added?
The manual states that 1050 for pre-88 and 850 post-88.
If this is true I should use only 26.008 ounces if it was based on R-12.
But trying to follow your logic I filled it correctly. Well I'm still confused which is not hard to do

Tampa 928s

Manual states:
R-12 up to 88 1050-10%=945 grams=33.338 oz (what I have in now)
R-12 after 88 850-10%=765 grams=26.9845 oz
If manual referencing R-134a post-88 grams=29.9828 oz

So the question is 26.9845 oz based on post-88 R-12;
29.9828 based on post-88 R-134a, depends on when the 928 switched over to R-134a and how the manual is referencing it.
In either case I am overfilled by 6.3535 or 3.3552 onces.
Confused yet, I am?
Damm I just need a base line number that's all

dprantl

Sorry, I misread your post. I thought you added 1050g without removing any percentage. You added the correct amount of R134A.

300psi at 3,500RPM is a little high, but not really a problem. Does your auxillary fan work? How's the fan-clutch on your viscous fan?

Dan
'91 928GT S/C

Tampa 928s

I have a S/C and 4 Electric fans and the front mounted fan also. I bleed off a little R-134a while monitoring my Temp. Got it down to about 27/250 with the first warm up went to 33.5 Degrees at idle. As it heated up and its hot 36/280 at idle and 25/325 at 2k Rpm. outlet temp 44.5.
It seems I may have an air flow issue?