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Insufficient cooling in my mercedes 300e 1989. When i hook the manifold gauge and turn on the AC, the low side pressure shows ~70psi and high side 200 - 230psi(low side pressure stays constans and high side not to)

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1989 year would indicate the system uses the Old CFC R12 refrigerant. 70 PSI equals about 70°F . This is not enough pressure difference to give you any cooling. Sounds like your compressor has bad valves. Replace compressor.

Posted on May 01, 2008

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there is no suction at all when the machine is off as the gas equalizes around the system
all you will read is the pressure of the gas in the system and that will tell you nothing
to read gas pressures you need to know the type of gas in the system , have gauges that can handle the high pressures and have two on a manifold so that you can read suction and high side pressure differences
That way you can see if the system is low on gas or over charged

Feb 24, 2016 | Sanyo Split System Air Conditioner

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High head pressure on high side, & very low pressure on suction line while heat pump is in heating mode? What is the cause ??

First you need to know that manifold gauges are supposed to be reversed in heat pumps during heating cycle checks. The causes of high pressure are 1. Dirty filters, 2. Dirty coils, 3. overcharged system, 4. obstruction in coolant lines.

Oct 05, 2015 | Heating & Cooling

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How do you put in 410a into Ac unit

You turn system on to cool setting and run temp down until outside unit comes on. Then you connect your suction side of your gauges to the suction side of your outdoor unit. Next you connect the liquid(high)side of your gauges to the liquid line on your outside unit(the little copper line). Connect the middle hose of your gauges to the 410a drum of refrigerant. Before opening the suction or low pressure side of the gauges you need to turn the drum upside down and turn drum of 410a on. Then you need a temp reading meter and clamp to read the temp of your liquid line(small line). While charging you want to make sure to release refrigerant slowly. The unit should call for a specified subcooling on unit plate. 7 to 10 degrees. You take the liquid line temp and subtract it from saturation temp on the high side of your gauges.(it'll be the pink numbers on the right side of your gauge.

Jun 05, 2013 | Heating & Cooling

2 Answers

My gauges are showing 60 low side 475 high The air is some what cold. comperser is running

I thought I answered this You discharge pressure seems a bit high but if its hot inside th house it w might be right. but your suction pressure seems a bit low for that high a discharge pressure . let it run for a while and check it again. be certain that you purge a bit of gas when you hook your hose up just a little mind you

Jul 23, 2011 | Carrier 38CKC042 Air Conditioner

1 Answer

Compressor clutch not engageing, ran a wire from alternator and clutch does work fine. leaving me with the impression that there's a faulty switch or sensor. don't know were to look.

Hi, when a compressor clutch does not engage on its own, it is more then like lost its freon, and is off on its low pressure switch, or low enough for it not to engage. It will start if you bypass the low pressure switch as you did. If you start your car, turn the ac on, and jump it out it will start to cool right away if it has freon in it. It will not burn out anything if you do it for only a few minutes. But, the compressor is good, and I doubt very much if its a relay to the pump. If this auto is older and has the valve depressor fittings for R-12 and not R134A, you can depress the high side, smaller line and it will have lots of pressure on it. I would go to the auto parts store and get the charging hose with gauge and can, hook them up to the low side large fitting if it is R134A, and you will know by the pressure on the gauge if its out or low. If you pierce the can to add some, the clutch will engage on its own, and that will tell you you have a leak. Depending on how long it lasts, will tell you how large the leak is.Doing this will save you lots of $$$$. Please let me know the outcome, but I am 99% sure you have lost the charge if you can jump it out.
A/C, & Refrigeration Contractor

Jun 12, 2011 | Heating & Cooling

2 Answers

I have the correct Manifold Gauges for checking the low and high side of the heat pump. How do I read the gauges to ensure that my system has the right charge? Outside ambient temperature is 85.4.

In order to know if you have the correct charge you must measure the subcooling since it is a txv unit. The outside unit will have the proper subooling you need printed on the data plate. Hook up you gauges and let thebunit run for 10 minutes, after 10 minutes check the high side pressure, that high side pressure will correspond to a saturation temp, write that number down then measure the temp of the liquid line and subtract the saturation temp from the liquid line temp, it should be the same as printed on tjhe data plate if it is higher than that add refrigerant untill you get whtas printed on tne data plate. Is there is no data plate use 12 degrees of subcooling.

May 27, 2011 | Heating & Cooling

3 Answers

I have a Samsung AQV12JA. Fault code (Gas leak) have replace the outdoor and indoor thermistor per tech line. They said replace outdoor computer board. Board was back ordered for over a month, this is a...


As per the error code there should be gas leak from the Air Conditioner. Please visit the link below for a complete service manual with diagrams for more details, I hope it should help:

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Sep 07, 2010 | Samsung AS18A6RB Air Conditioner

1 Answer

How do i hook my manifold gauges to my residental condensing unit to check pressures

The AC manifold gauges set have the three chambers: the low pressure chamber (left side), utility chamber (middle), and the high pressure chamber (right side).

When technicians connect the HVAC manifold gauge to the air conditioner units, he connects the low pressure side of air conditioner unit to low pressure gauge side.

If he wants to read the pressure in discharge line he connects the high pressure gauge hose to the air conditioner high pressure side.

The utility port (the middle chamber) is a place you connect the hose to vacuum pump, recovery units or add or remove refrigerant from AC units.

Air conditioning gauges is used to measure air conditioner units pressure within closed-system to evaluate or troubleshoot the AC units. Gauges manifold set is the most frequently used item when it comes to refrigerant or pressure.

Air conditioning gauge set allows the HVAC technician to check AC units operating pressures, transfer AC refrigerant, pressure test system, purge the system with nitrogen, and perform other necessary tasks.

The gauges manifold set includes the hoses, the manifold, the valves, the compound gauge (low pressure gauges) and high pressure gauge.

Jul 24, 2010 | Heating & Cooling

2 Answers

Air not cold enough to cool house

Make sure the outside fan is running. Also check the high side pressure, I assume the 70# is the low side pressure, so you can tell what the compressor is doing. If the fan and compressor are both working, make sure there is good airflow through outdoor coil and check that it is clean. Let me know what you find.

May 17, 2010 | Goodman CLJ24AR32 Air Conditioner

1 Answer

How to use it

Subcooling - The difference between the temperature of the Small copper line (Liquid Line) and the high-side (red) gauge temp on your manifold

Superheat - The difference between the temp. of the Suction line (Big copper) and the low side gauge (blue) temp

Apr 26, 2009 | Carrier Heating & Cooling

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