R12 A/C regassing

[river]

Hi,

My question wasn't really a question

Then should you not of used an exclamation mark instead of a question mark at the end of your rhetorical question?!?

seeyuzz
river

[Mos]

I didn't wanna appear like too much of a bunghole

BTW, it's should have, not should of

[CrUZida]

Care to explain what/where this hydraulic regulator is ?

[BrianRA23]

Isn't it built into the compressor (? or !)

[Mos]

The big weird looking thing on the source of the compressor suction hose and on the outlet of the evaporator, usually on the passenger side lower strut tower. It also has a connection to the expantion valve in the evaporator (the copper tube on top).
(I can look for pics if you really really want to, but I'd rather I didn't have to .. look for some empty MX83 engine bay pics).

Apparently this device regulates the amount of refrigerant it allows into the compressor, so that the evaporator remains at a specific temperature (somewhere above zero). Don't ask me how it works - this is based on snipets of information confined to memory over a decade - I'd really like it if someone could explain how it actually worked

Mos.

[river]

Hi,

Apparently this device regulates the amount of refrigerant it allows into the compressor, so that the evaporator remains at a specific temperature (somewhere above zero). Don't ask me how it works - this is based on snipets of information confined to memory over a decade - I'd really like it if someone could explain how it actually worked

The device is called a Thermal Expansion Valve (TVX) which is basically a valve that controls the amount of super-cool refigerant that goes to the evapourator.

The temperature differential of the evaporator inlet and outlet typically determine the opening and closing of the TXV seat to either add (flood) refrigerant flow or constrict (starve) refrigerant flow to the evaporator.

And, from Wikipedia....

A thermostatic expansion valve (often abbreviated as TXV or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of superheat at the outlet of the condenser. This is accomplished by use of a temperature sensing bulb filled with a similar gas as in the system that causes the valve to open against the spring pressure in the valve body as the temperature on the bulb increases. As temperatures in the evaporator decrease so does the pressure in the bulb and therefore on the spring causing the valve to close. An air conditioning system with a TX valve is often more efficient than other designs that do not use one.

A thermostatic expansion valve is a key element to a refrigeration cycle; the cycle that makes air conditioning, or air cooling, possible. A basic refrigeration cycle consists of four major elements, a compressor, a condenser, an expansion val ve and an evaporator. As a refrigerant passes through a circuit containing these four elements, air conditioning occurs. The cycle starts when refrigerant enters the compressor in gaseous form. The refrigerant is compressed by the compressor to a high pressure and temperature state. The high pressure and temperature gas then enters the condenser. The condenser changes the high pressure and temperature gas to a high temperature liquid by expelling heat either to the ambient air or a fluid similar to the action of an automotive radiator. The high temperature liquid then enters the expansion valve where the valve acts on the refrigerant and changes it to a low pressure and temperature liquid. The low pressure and tempurature liquid is now suitable for cooling. The low temperature and pressure liquid enters an evaporator which heat is absorbed from air or another fluid and the cooling action takes place. After exiting the evaporator, the refrigerant is now a low pressure gas. The low pressure gas enters the compressor and the cycle repeats.



seeyuzz
river

[Mos]

You've quoted what the expansion valve is, but not what the hydraulic regulator thing is...

[o_man_ra23]

You've quoted what the expansion valve is, but not what the hydraulic regulator thing is...

I thought it was one and the same?? You described that the "hydraulic regulator thing" is on the lower passenger strut tower... exactly where I found the TVX in a mate's MX83 which was faulty. From looking at the pipework, they regulate the heat as per River's description, with the compressor working with full gas flow all the time (starving the compressor of gas would possibly give cavitation would it not??)

Personally I am going to fit A/C to my originally non refridgerated RA28 in the nearish future, and I live in an area which is rather stinky hot. On a hot day, doing a highway trip at 100kph, the missus' excel will lose AC after about an hour or so of driving, and won't get it back until half an hour after you turn the bugger off (by which time the car is stinking hot again). I might have to throw on a bigger thermo?? (Was regassed, pressure tested, leak tested, had a new hose fitted due to leak and new R/D just prior to this becoming noticed - died from lack of gas just before that)

So... what sort of donor vehicle would be a good source for an efficient condensor - will be running an AE82 compressor already converted to R134A (although some of the oil is sitting on my shed floor, so I will need the oil topped up) and I will be custom making the mounting brackets anyway. Also, any tips on maintenance to do to the evaporator while it is out of the car other than wash the exterior of the core??

[CrUZida]

Bigger thermo won't do a thing at high speeds.
If the aircon is tripping out after an hour then you have major issues. Also if it takes 30mins to come back on you also have major issues.

While at speed there should be more than enough air to keep the gas cool. Make sure the condensor is free from debris. It sounds like the gas is heating up and then taking aaaages to cool down. Its also possible that the over pressure switch is faulty, and tripping at a lower pressure than it should, and resetting at a lower pressure than it should.


As for evaporator maintanence, just give it a good wash, and get it pressure tested. They are a common point of failure, and any leak in there cannot be diagnosed without pulling it out.

[Mos]

I thought it was one and the same?? You described that the "hydraulic regulator thing" is on the lower passenger strut tower... exactly where I found the TVX in a mate's MX83 which was faulty. From looking at the pipework, they regulate the heat as per River's description, with the compressor working with full gas flow all the time (starving the compressor of gas would possibly give cavitation would it not??)

The TX valve on toyotas is fitted on the evaporator and it's on the inlet and not the outlet - remember it regulates how much liquid refrigerant is allowed to vaporise inside the evaporator.
The MX83 thingy is not the TX valve, though it connects to it. An MX83 has this regulator thingy, many cars do not.
I guess I'll have to take photos....

excel will lose AC after about an hour or so of driving

Excel air con sucks big time. That is all.

So... what sort of donor vehicle would be a good source for an efficient condensor

Whatever fits you don't exactly have a lot of room....

Mos.

[HKS_TRD]

Is the evaporator the thing in the box in the inerior that you conveniently have to either remove the entire dash of the firewall(jk) to get go?

Does R12 emit have a characteristic odor at all if it is leaking inside your car?

[o_man_ra23]

Yes, evaporator is the bit which sits inside the cabin.

Can't say I disagree with the comment of excel A/C sucking. Can't wait till we ditch that thing and buy a new car for the wife (she seems adverse to getting a 1UZ Celsior )

[CrUZida]

Best pic I have.

[wa5]

with the Excel A/C issue, is it possible that it has too much gas in it.. causing it to over pressure when it has been operating for a while and thus tripping the over/under pressure switch and cutting the system until it all cools down?

[Talasas]

Excel air con sucks big time. That is all.

Mos.

I drove home from Mallala on a 43°C day in full sunshine in a 96 Excel and the air con worked fine. The car had been in the sun all day as well, it was effing hot inside but nevertheless the AC worked well. We've never has a problem with it.

I have seen better though, I remember I drove an XU6 Commonwhore on a hot day and had to turn the AC off for a bit because I was getting cold, maybe we should hunt in the Holden parts bin for AC bits?