FAQs about low refrigerant or refrigerant undercharge effects on air conditioners & heat pumps or other HVACR equipment:

This article series explains the symptoms of and problems caused by not enough refrigerant in cooling equpment.

Effects of Undercharging the Refrigerant Level in an Air Conditioner, Heat Pump, or other refrigeration equipment

These questions and answers about how lost refrigerant, low refrigerant, or under-charged refrigerant in an air conditioner or heat pump will be apparent were posted originally at UNDER CHARGED REFRIGERANT, EFFECTS - be sure to see that information.

On 2018-11-24 by Anonymous - will compressor start up if there's no refrigerant?

Yep, the compressor will (usually) run but of course isn't compressing anything so will have no effect.

On 2018-11-24 by glenn

if no refrigerant in new heat pump will the compressor start up

On 2018-07-10 by Anon

I had a Lennox EL16 and evaporator coil installed a year ago. It had to be filled with refrigerant three times in a year! Am I justified in demanding a new unit be installed as there may have been damaged caused by running low refrigerant?

On 2018-02-08 by (mod) - many HVAC equipment problems are traced to a bad connector

Thanks for the follow up, it's an important reminder that great proportion of problems with electrical equipment is in the connections.

On 2018-02-08 by Anonymous

I am STUPID STUPID STUPID. Installed 3 n 1 relay, Nothing. Started all over again. Electrical first. Pulled timer. Re seated.

Kiss my --- if that compressor didn't start up. It was a brand new timer, just installed it 6 months ago. Bad connection??
I put the original start relay and overload back in -- A OK.

Just goes to show. MAKE SURE U re-seat all your wire connections first, even if you r sure there good, check it again and again !!!!!!!!!!!!

Should have know. Had a problem with my desktop, would turn it self off - bang. And restart, over and over. Pulled hard drive and RE-SEATED
cable, been working fine ever since.

On 2018-02-07 by (mod) -

George

Often there are generic repair parts that work just fine, such as hard start capacitors in the appropriate uF range for the motor.

Keep in mind that even adding a hard start capacitor you may be getting at best a bit more life out of a motor that's at end of life and will seize again soon.

As many readers have commented, a corroded or simply loose wire could be the trouble.

On 2018-02-07 5 by George

Well after much research they might look alike but there not. I gotta learn to b more careful. I cannot find a Refrigerator Compressor Start Relay that fits my model #.
SOL I guess. 3 in 1 hard start kit it is.
# 3ET22KDXFW00 It's only 20 yrs old. Come on.

On 2018-02-07 by George

Going to try a 3 in 1 hard start kit. Just to see if compressor will start.

Replaced the start relay but maybe it wasn't the right part. It was pretty cheap. $10.00.
Found these start relays on the internet ranging from $10.00 to $60.00.

Opted for the cheap one. If the hard start works I'll get one from Sears for more $.
I don't understand the price difference through. For my model they all look the same and claim to be universal.

On 2018-02-06 by (mod) - why won't my compressor start?

I would not expect low refrigerant to prevent a compressor motor from starting. I would look first at electric controls like timers and relays.

On 2018-02-05 by George

I have a 1998 Whirlpool refrigerator with a compressor that won't start. Cold control and timer check out OK, both have been recently replaced. ( checked em anyway )
Tests on compressor ( ohms, continuity test ) OK.

Replaced start relay and overload. I have power at compressor terminals. Still won't start. ?? It was not getting very cold at top temp setting prior to the compressor failing to start. Suspected the fridge was low on a Freon and was going to check and charge if needed.

I'm not a pro, but can usually find the problem. Is the compressor motor seized up? Any help - suggestions what to try next or is it time to have the old girl recycled.

2/4/2018

On 2017-11-27 by (mod) -

Anon

Well, well it is certainly the case that everyone is not always correct, it is true that when the refrigerant charge is low in assisting you may develop an abnormally low pressure on the suction or low side.

I can explain why you see abnormal icing on the evaporator or cooling coil. Eventually when the refrigeration leak continues and you lose all refrigerant then you won't have any cooling.

On 2017-11-27 by Anonymous

kk . every one is saying that low pressure is created if their is low refrigerant .


tell me HOW this low pressure is created if their is low refrigerant?

On 2017-10-31 by (mod) -

I'd look at both the refrigerant charge and also a debris-blocked thermostatic expansion valve or reversing valve.

On 2017-10-30 21:59:31.264166 by Jake

Installed new 5t heat pump late fall northeast ohio,charged it with my tech bestto we could under those conditions

ran great all winter,was getting 105℉at first retired closest to furnace,in summer we checked/adjusted the pressure,in a while(many days) we discovered a loose cap,there was some gas leakage,checked /adjusted pressure again, this fall can't do better than90℉ ish for temp.any ideas why loss of heat/ temp?

On 2017-10-21 00:28:55.479341 by (mod) -

Juan

Icing on the coil of an indoor or cooling coil can be due to low refrigerant, as we discuss in UNDER CHARGED REFRIGERANT, EFFECTS https://inspectapedia.com/aircond/Refrigerant_Undercharge.php (this page)

Or anything that obstructs air flow, like a dirty coil or crushed return duct can have that same result.

Low refrigerant can damage the compressor motor in an A/C or heat pump system, by what I'd call an "indirect" effect. That is, before the system has failed totally or produces no cooling whatsoever (thus the occupants notice and do something like call for repair) the compressor may have to work longer/harder on-cycles, perhaps overheating and leading to damage.

But other failures can also cause the problem you name, like a bad start/run capacitor. So typically a service tech might first try swapping in a new capacitor, or she may perform a more expert test measuring voltage.

Meanwhile leave the system OFF in hope that we don't destroy a salvageable compressor motor.

On 2017-10-20 by Juan Manuel

Hello. I have a 24000 BTU samsung split a/c, the indoor unit (evaporator) frozed without me noticing it. When we tried to start the air conditioner the next day the compressor only hums for 3-4 seconds then stops. Then it will try to start again but it can't. When the a/c compressor tries to start the lights dim

On 2017-05-16 13:59:38.456744 by (mod) -

Joseph

Yes the compressor may still run, but no cooling will occur.

On 2017-05-16 by williamsjr.josepht

If you central air unit is completely empty with no refrigerant will the compressor still come on?

On 2016-04-06 by (mod) - frosty TXV

I am not sure anon, but I'd take a look at the high side pressure too. If high side pressures are low then the compressor may be in trouble.

On 2016-04-06 by Anonymous

15 year old Goodman 4-ton Heat Pump with TXV. The heating worked well throughout the winter but the first time I used the cooling, the TXV became covered with frost. I suspected undercharge which was confirmed by low head pressure and bubbles in the sight glass.

I found a small leak, repaired it and then added a few pounds of Freon to clear the bubbles. The head pressure came up to about 220 (82 degree day).

However, frost still forms on the TXV and the suction pressure is around 20 psi. I opened the TXV to its most open position and the suction pressure came up to about 28 degrees.

Suspecting possible trash in the system, I removed the TXV and blew it out with compressed air. Reinstalled it and pumped down the system. The problem (low suction pressure) persists.

Tapping on the valve and warming the sensing bulb had no effect. I suspect a bad TXV. Is that the most likely problem?

On 2016-01-24 by (mod) -

I don't think so - that is, low refrigerant won't keep a compressor from running on most systems.

On 2016-01-18 by Jack

If low refrigerant is the cause of my automotive a/c pump not engaging, should I see voltage at the electrical supply plug when all the controls are set for the air conditioning to be running ? Thanks for any help you can provide.

...

Continue reading at UNDER CHARGED REFRIGERANT, EFFECTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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