Alan

So your pusher is stock (or stock style) - how is it controlled? also like stock - just on(full)/off. Then you have Han's dual puller on the other side of the rad controlled by the new variable speed fan controller?

When the AC is on does the puller also bump up to some fan level? is there a good seal/ducting between the condenser and the rad to ensure no short loop recycling of warm air around the bottom of the condenser?

Alan

Ducman82

correct. stock AC, comes on via hight rad temp, or the trinity switch. hans fans run by a progressive controller. shroud sealed to the radiator with foam tape/edging. when AC is activated, main fans throttle up to 50 percent.

Alan

OK that sounds like it should be fine - so maybe it is an overcharge... It does also seem that your high pressure switch isn't matching the spec you noted very well...?

Alan

Ducman82

Ya, seems it's about 35ish psi to early. Could be its tripping before the gauge gets the high.

Ducman82

so another hot day(feels like it) about 84ish here and i went out an played with the AC again. i let a tad out, of course i have no way of knowing, but the AC gauge lines have valves in them so when the lines are disconnected they hold a lot as well. at any rate, here is how she did today. and NO compressor cycling. tomorrow should be hotter, so ill try again then as well. all testing done in a hot garage.

j.kenzie@sbcglobal.net

It's a little hard to know, but your inside temps are improving. Your OAT may be 84 degrees F., but due to engine heating and perhaps limited fresh, cool air availability, your condenser may be seeing a higher temp. Try holding a digital thermometer a couple inches in front of the condenser. 84 degrees F. should give you about 215 PSI at the high side. You seem to be getting better, but may still be a little overcharged.
Dave

Ducman82

ya, it gets pretty toasty in the garage. the one spot on the condenser i am measuring the temp at seems to be around 145 (driver side near the headlight arm)

should be near 90 tomorrow, so I'm sure it will be nice and hot.

YES a 10 degree drop. i am happy with that!

j.kenzie@sbcglobal.net

In order to use P & T charts, you need to measure the air temp 2" in front of the condenser. That is what determines proper hi side pressure, ie. 90 degrees F gives 238 PSI.
Dave

Speedtoys

It doesn't matter what the temperature is..it should match that appropriate pressure for that temperature.

You could do it right now, at 10pm tonight, or 98d next Wednesday..

Ducman82

I'll hunt down a chart.

griffiths

If your condenser/fan function is equal to or better than original.
On a "90ish" ambient your high side should be about 238 psi at idle.
Things look good until your engine temp rises.

If you have the time and patience I'd start over again with the AC charge.
Remove refrigerant, proper evacuation.
R134a 85% by weight of the original R12 charge.
Refer to the the high side P&T provided to you in the previous post.

Ducman82

i was looking at a P & T charts, looks like my suctions side might be a Tad low for the ambient. hmmmm.. maybe a compressor issue manifesting its self.. hmmmm

griffiths

I'd focus on the high side for the moment, your low does not look too bad.

Ducman82

copy that

staying the course

dr bob

I'm loosely following the discussion here, loosely thanks to a slew of other commitments. So I may be a little late to the party. Regardless...

The pressures and temperatures in the tables ASSume that you have heat exchangers (condenser and evaporator) that are 100% efficient. They also ASSume that there are no parasitic heat losses in the system. With that in mind, you can confirm the presence or absence of air in the system only with the car at a stable temperature and not running. Read the low side gauge, compare with the pressure/temp chart to get that out of the way. After that, the system should be charged to get the low-side pressure equivalent to the evaporator vapor-side approach temp at about 5-15º below freezing. That will typically get you the ability to make ice at the evaporator, and let the 'freeze switch' control the compressor cycling so that the cabin air vent temp is as low as possible without icing the evaporator. Then look at the corresponding high-side pressure, and also at the sight-glass. The high-side pressure should be be no greater than the corresponding ambient temp plus about 40º worst case. If it's close to that ambient-plus-40º pressure, you have an airflow problem or something that's else keeping the pressure high (like a malfunctioning expansion valve or a partially-blocked drier). Airflow problems leave bubbles in the sight glass (too hot for the pressure), while partial blockage raises the pressure while there's plenty of cooling, leaving few or no bubbles.

The refrigerant pressure/temperature charts give some guidance on what to expect, but they apply to the refrigerant temps inside the tubes of the exchangers. Looking at the differences between measured and calculated temps guides you to where the system is working and where it isn't keeping up.

Keeping the heat exchangers clean is critical to system performance. When the condenser can't shed heat because of airflow restrictions or fouling, the whole system pressure goes up. The compressor is a pump, where a high discharge pressure (due to high ambient, low condenser airflow or condenser fouling) translates into less refrigerant being pumped. That in turn raises the low-side pressure and the evaporator's ability to gather heat from cabin air.

The system is to a certain extent self-regulating, since high discharge pressure means a bigger difference between condenser temp and ambient temp. That -should- cause more heat to be transferred to the passing air, but there needs to be enough of that 'passing air' to actually carry the heat away. At the same time, elevated condenser pressure elevates the compressor inlet pressure (and the corresponding boiling point of the refrigerant in the evaporator) so less heat is extracted from cabin air. This is something that happens on a continuous/ongoing basis, subject to changes in compressor speed, cabin temps, interior fan speeds, airflow across the condenser, ambinet temp of course, and also to the temperature of the air being drawn into the evaporator.

A seldom-remembered component in the heat balance is cabin-air humidity. A certain amount of the heat exchange capacity is spent condensing water from the cabin air. The evaporator extracts a certain number of calories from each gram of air, one for each ºC of temperature change. Once the evaporator gets down to the dew point for the cabin air, it takes about 100 calories removed to get that humidity to condense to liquid before the air will cool any more. The effect of the removal of the humidity is apparent to the cabin occupants as the air can then cool them by evaporating more perspiration. But the vent temps won't actually drop until those extra 'latent heat of evaporation' calories are spent condensing the humidity. Again, this is a somewhat self-regulating process. I wanted to remind readers of this, so that they understand one other reason why there can be a bigger difference between calculted boiling temperature of the refrigerant in the evaporator and the actual center vent air temperature on a hot humid day, vs. a dry desert day at the same temperature conditions. Oh, and 'dry air' is denser than 'humid air', so carries slightly more heat from or to the exchangers. Some readers in high-humidity conditions may find that the system capacity is not sufficient to condense all the available moisture in the cabin air; the symptom of that is cabin venter vent temp that hover near the dew point of the humid air. On a 100º day with 95% relative humidity, the system needs to work extra hard just to get the evaporator outer surface temps below 96ºF, pulling all those calories out of the air and moisture to get the moisture to condense before the sysem can seriously cool the cabin air any more. Jake is enjoying the relatively dry desert climate in Los Angeles right now, so humidity is not a huge consideration in the heat exchanger wars.


HTH!