Ah, useful data

I was running the engine with the manifold on and the service line feeding goo. 
   I have a chart that lists both high and low side at specific temp in f and 
C.   The system was showing pressures consistent with the chart, but the charge 
was low.   The IR probe was not used to measure at those places specified.

I have not tried the rest pressure test.  Figured it would show what it would 
but that would not be indicative of useful data.  I do know how much goo was 
injected, as I have evacuated the system, such that there should be nothing 
left inside prior to beginning the charging.  I should be shy 24oz.

I did take the car out for some short (under 10 mile) trips and was pretty 
impressed with cabin temps and cooling.

clay



> On Jul 15, 2017, at 12:26 PM, fmiser via Mercedes <mercedes@okiebenz.com> 
> wrote:
> 
>> clay wrote:
> 
>> I evacuated the system once more (it had been tested overnight)
>> and did a refill.  Well, sort of.  It calls for 3.3# of R12.
>> There is a pressure/temperature chart that gives pressures based
>> on outside temp.  Using that, I reached the required pressures,
>> but am short on volume? 
> 
> At rest pressure CANNOT be used to figure out how much is in the
> system.  Once there is about 20% change, the at-rest pressure will
> match the chart.  It won't change until thy system is
> over-charged.  That's the nature of gas. (not gasoline/petrol)
> 
> With the compressor running, looking at the low side pressure can
> give a pretty good clue as to the change.  The high side doesn't
> tell much about charge.
> 
> Weight is the most consistent way to determine change.
> 
> That's hard to do on an partly-changed system 'cause it's hard to
> weigh what is inside.  Without a machine to remove it all, (and
> scrub it clean and weigh it before putting it back in) the only
> way I know is to monitor temperatures in the evaporator. Checking
> inlet and outlet temperatures can be enough.  A no-contact IR
> thermometer is handy - but remember most of those are calibrated
> for black, not aluminum, surface.
> 
> Out of the compressor should be hot.  Out of the condenser should
> be quite warm.  After the expansion valve and inlet to the
> evaporator should be cold.  Out of the evaporator should be about
> the same or a bit colder.
>  


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