Its Hot My Suction Line's Not

fatbillybob

First thanks for your help. I am familiar with auto A/C units not central air.


1-My pressure guages read 130psi on both hi and low side. Label on compressor reads 150psi low and 300 high. So it looks like my compressor is not doing its job or it is not coming on dispite my fan blades spinning.

2-A relay is kicking in but the fan blades do not spin unless I help it to get started then they spin just fine and I hear no bad bearing noises. This is unrelated to failure to spin due to too high head pressure on immediate shut down. I cannot get high head pressure as evidenced by problem 1 above.

3- Can the fan motor spin when the relay is switched on yet the compressor not run due to a clutching mechanism like in a car.


Besides getting a replacement unit what are the fixes? Is the no spin on the fan blades due to undiagnosised bad bearing friction or failure of a "high start capacitor assist"? Is there a pressure switch in Central A/c systems that sence the 130psi as too low a pressure such that it prevents the compressor from working similar to a car's low pressure switch that prevents the compressor from compressing nothing when the freon is too low.

fatbillybob@yahoo.com

bigjohnsons34

sounds like a bad capacitor, it probably has a duel cap and it is shot but with out looking it's tuff to say..

fatbillybob

Agreed! but don't you think the capacitor is an independant issue and I have two problems? If I do the capacitor's job by starting the fan spinning then the unit takes over I still get no cooling and the guages read the same 130psi on hi and low side. Is there typically a feedback on bryant units that kill the compressor if the cap does not work?

mdshunk

If you're getting the exact same pressure (or nearly the same pressure) on the high and low side while the compressor is running, you have shot valves in the compressor. There's no two ways about it. The only repair option for a hermetic compressor is replacement of the compressor.

(If, by chance, this is a heat pump, you might have a reversing valve blown out).

fatbillybob

O.K. thank you. Can the fan motor work and blow air and the compressor not turn? I am not familiar with compressor condenser central unit design.

mdshunk

So you're not even sure if your compressor is running? Time for you to bail out.

fatbillybob

Thank you for the constructive crit.. I have never taken one of these things apart but it is just a unit to me. Basic. It was a simple question. Like I said before I am familiar with automotive. The principals are the same. In car we have a clutch that allows the fan to spin yet the compressor can be off. So let me ask the question another way. Does a central A/C compressor/condenser unit have a clutch? My guess is no. But I had to ask or take it apart. Asking is easier.

mdshunk

No... the motor and compressor in a residential unit are hermitically sealed in a black or tan metal can. If you intend to fuss with this some more, determine if your compressor is actually running or not. Sorry so harsh, but you don't seem too mechanically inclined if you didn't even determine this before you stuck the gauges on.

Are you aware that you do need the EPA art 608 cert just to install gauges on the system? The fines are permitted to range up to $27,500 and 10 years in federal prison. I am 110% certain that you don't have that certification.

fatbillybob

For what it is worth this is just not a hard job. It is just mechanicals. My questions are from lack of understanding central air design not from mechanical ability. Also, vendors will not sell you the stuff you need without the certs. So for anyone who would like to take the voodoo out of this job and don't have the certs you can start here

hf05

split capacitor is hooped.pull your meter out with power off and check mf

snapperhead

the compressor is off and equalized at 130 psi,hook your guages up and bump the compressor contactor in with a pencil see if the pressures rise on the red and drop on the blue..fan or no fan then let it out.if you pull the cover and the contactor is in the compressor is shot,most residential powers the condenser fan off the compressor contactor cost effective!!!!

ATS

Post Delta T, subcooling, superheat and MFD and amperage readings and maybe then we can help you.

mdshunk

Freaking beautiful. That'll sort out the posers in a hurry.

Genesis

my thoughts are that it could very well be a dual capacitor which has three ports for connection one side for fan one side for herm which is the compressor they share the common. Kill the power to the unit and first check to see if capacitor is swollen and if it's not set it on a flat surface and see if it has any rocking to the capacitor they will set perfectly flat if they are still good ( only the metal capacitors will swell up and bulg out the plastic kind won't) if you don't notice any of this get a multi-meter and and set for uf which is micro ferits and check between the common side and herm ( commpressor ) and the common side and fan. then check for label on capacitor to see how much each side should have example: 5uf 50uf and you have to remove the wires from capacitor to check this remember which ways the wires went on maybe write it down