A/c hose restrictions

[Mike L]

Is the compressor cycling or just staying on? I’m curious as to what the pressures do when the comp. cycles. Also, I did an a/c job on a Volvo loader a while back. The book calls for about a 4 lb charge. When I put 4 lbs in it my pressures spiked and it wouldn’t cool. Everything else checked out but for whatever reason 3 lbs was the magic number on that particular machine.

 

[rmllarue91]

Compressor doesn't really cycle much when it does pressures start to neutralize normalish speed ? Vent temp is 60s. I have charged by performance if I under charge it almost looks promising (like itilow on charge) if I over charge works good when ambient temperature is 60s and low 70s. The red dot guy says the pressures aren't whole issue. Idk if the expansion valve is working and condessor has lots of air flow why won't the expansion valve get cold? I've got like 40 hours between working on machine and travel time. I can't bill all that so now I'm loosing money and having to admit Im in over in over my head puts this job is number one on getting off the list. I feel I have a decent understanding of a/c but just not the experience diagnosing. At least being out of comfort zone usallus leads to learning..... Thanks for all the discussion can't wait to get some temp probes and give the water on condenser a try.

 

[Georgia Iron]

I am not a tech but I have installed and trouble shot my own system....

Does it have an inline filter or an orifice tube... I do realize no orifice tube is used on a expansion valve/receiver-drier set up unless it is a dual setup.


I would feel the lines near the compressor, use your hands. Is one cold? Is it running...

200 psi does not seem high enough.. low in these temps? I would have thought it should be higher.. Is the belt tight on the compressor pulley? Is the compressor cycling, if so why does it turn off? High pressure low pressure... garbage compressor? Maybe your termostat sensor has vibrated loose from the evaporator cooling fins or maybe it is too close and touching?

I installed a complete system and did not realize it had a cut off/on sensor (thermostat) inside the case, sealed it all up and could not figure out why it would not call for the compressor to cut on... cost me 2 days and had to cut it all back apart...

Is water forming on the evaporator?

From what i learned working on my own... it came done to the temp sensor on the fins too far off and it would freeze, to close and it would not get cold enough... and a fan on the condenser... used gauges as a base line but charge was utimately based on max system cooling based on temp out of vents and hose temps...

Condenser needs to be on a certain angle to correctly accept charge.. It should cool with out a fan but the fan should help drop the temps by 10 to 15*, I installed one on a relay controlled by compressor call voltage... worked like a charm and it was an add on....

How does a blockage occur on a system unless you have a major part failure it is a closed system...

Your expansion value might be wrong the machines use the heavy duty type (block type as fun with fuel stated?) not the cheaper light duty automotive type ... At least thats what was on my case....

I bet it is a real pain trying to find the gremlin in the field. I don't believe I could have done it. Took me more than a week to install and another few days to trouble shoot all my issues.. Tell them its time to ship it you so that you can properly trouble shoot it... Bet they dont like that...

 

[rmllarue91]

Debris and contaminates internal can come from compressor, lines, drier, orfice tube expansion valve external possiblity s are endless lol this never work right since customer got machine always works at low ambient temperature never above 80.

 

[Birken Vogt]

200 psi does not seem high enough.. low in these temps? I would have thought it should be higher.. Is the belt tight on the compressor pulley? Is the compressor cycling, if so why does it turn off? High pressure low pressure... garbage compressor? Maybe your termostat sensor has vibrated loose from the evaporator cooling fins or maybe it is too close and touching?

That is kind of what I thought at first but he is low ambient, 75 or so, so 200 would be quite high actually. But really you need to have a thermocouple on the liquid out of the condenser to know for sure whether it is high or not.

15 psi low side is quite low, normally it would be 28-30 or clutch cycling regularly to keep from freezing. High high side and low low side generally means restriction, but it should get cold where the restriction is located.

I want to see how this one turns out, sorry for the OP's wasted time.

 

[Georgia Iron]

Debris and contaminates internal can come from compressor, lines, drier, orfice tube expansion valve external possiblity s are endless lol this never work right since customer got machine always works at low ambient temperature never above 80.

I bet it is a real pain trying to find the gremlin in the field. I don't believe I could have done it. Took me more than a week to install and another few days to trouble shoot all my issues.. Tell them its time to ship it you so that you can properly trouble shoot it... Bet they dont like that...

 

[rmllarue91]

Here's something I left out those pressures are at idle the press difference increasing as rpms are raised. Thermal couplings and a log book of temperatures would be super helpful at this time. There is a guy coming out on Tuesday so I'll post that night.

 

[Georgia Iron]

Here's something I left out those pressures are at idle the press difference increasing as rpms are raised. Thermal couplings and a log book of temperatures would be super helpful at this time. There is a guy coming out on Tuesday so I'll post that night.

I think i would do it at operating rpm.. or maybe 1800 rpm I think i read somewhere you must check the system at operating rpm... not at idle..

 

[funwithfuel]

200 at idle with fans blowing hard and maintaining 15 on the low. I think you were onto something by reducing the charge.
Under those conditions, I would want to see 0-5 psi on low and 150-130 on high. The fact that you're up to 200 and 15 .... just seems too high to me with the condenser fans running.
Sorry to hear you're taking such a beating on this.

 

[rmllarue91]

Don't be sorry guys its a business can't win them all
my dad always says education is expensive one way or another....

 

[Birken Vogt]

You keep saying 0-5 psi low side, you mean with the freeze switch locked out correct? I would never expect to see it that low in an operating system, the evap would freeze to ice in no time.

I always try to troubleshoot AC between 85 and 95 degrees outside temp, 85 because anything lower is meaningless and no challenge to the system, 95 because pressures start to get unreasonable and bad things can happen to your gauges (ask me how I know)

If it is a truck I will lock the fan on and set engine RPM to 1300 or 1500, ear protection required. But engine RPM must be middle to high regardless of truck or machine or car. If it is a car then some means of providing air flow must be provided, sometimes I even drive with the gauges stuck in the window.

Of course on a Red Dot system you have a rooftop with electric fans, no problem there.

As for the interior, recirculated air with the doors/windows open to get a decent amount of warm outside air but not too much hot air and definitely do not want to get any hot air off the engine/radiators.

 

[partsandservice]

Check to make sure the pressure line from the compressor goes to the top of the condenser, ran into this once on a red dot system with the separate condenser unit where the inlet and outlet hoses were the same size in side the box and hooked up backwards. Also make sure the drier is installed in the correct flow direction . And as mentioned before too much oil in the system will not leave enough room for the correct freon charge and will make head pressure spike with the correct charge. Flow should go through condenser then the drier

 

[rmllarue91]

Sorry about late reply been busy this ended up being the box had a panel missing blower was pulling warm air from out side..... The red dot guy checked my worked saw condenser was getting cold and left.... Later I found small panel missing it was a nightmare job. I really missed that one thanks for all the help I learned alot about a/c performance on this one