a/c pressure switch change - need to discharge system?

Angus · Post by **Angus** » Thu Apr 03, 2014 3:24 pm

In the event that I have to change my a/c pressure switch ... will I have to have the gas evacuated first, or can the switch be swapped out without loss of gas?

Not a problem if it needs to be discharged - I can have a bloke vacuum the R12 out (pressure test shows it still has a full charge, or as good as) and then put it back in for me. But no point doing that if I don't have to.

Alternatively, any reason why I can't just jump the wires going to the pressure switch and leave it at that?

K30DPC · Post by **K30DPC** » Thu Apr 03, 2014 4:09 pm

1. A/C system must be empyied first.
2. I wouldn't use R12 or any other gas back again. Refill with new one
3. Not sure about this. But in case of pressure drop your compressor will still running which will kill it. Also signal from this sensor may be used for something else. I'm sure there will be someone with better knowledge about this

Angus · Post by **Angus** » Thu Apr 03, 2014 8:01 pm

Thanks.

The refrigeration guy did mention that he had a couple of bottles of some gas that's apparently a direct replacement at the back of his shed. I must ask him about it. He works on fishing boat refrigeration units usually. I also have a neighbour who does industrial refrigeration, so he might have something lying around.

R-12 is not a thing you can get hold of new anymore, though, and I don't fancy using the more recent standard ones as I've read so many stories about seals being quickly degraded and so on.

Must look further into the jumper thing, though, if I'm going to have problems replacing the gas.

Post by **Thebusofwoe** » Thu Apr 03, 2014 9:30 pm

As i am sure you know you cannot use r134a in r12 systems. It will destroy seals, pump ect. The taps are also different between the two. On another note, i am pretty sure r12 is illegal to use now due to it being too much of a pollutant

There are however, people that will still gas/degas r12.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Thu Apr 03, 2014 9:50 pm

Yep, R12 is illegal but you can still dispose of gas that's already in systems (only way to deal with it

).

You can run R134a in R12 systems though (it's the only way to keep them going!). It's not exactly like-like though - the system will run at a slightly different temperature/pressure (R12 its less efficient, so the system has to work harder) and the lubrication qualities are different, so for those reasons it's recommended to use an additive lubricant so the seals and bearing surfaces can cope.

You can't mix the gases, need to fully vac down and replace.

Angus · Post by **Angus** » Fri Apr 04, 2014 10:06 am

Aye, certainly a chap shouldn't use R-12 nowadays. Being a bit of an environment protection chap I deal with such things every day.

However, there's always someone who's willing to work with it off the record - fishing boat refrigeration guys for example! Last time i needed my system recharged (in one of my Celicas) I happened to find myself in Hungary, where fellows with bottles of R-12 are surprisingly easy to find!

Nae taking the Lude there, though, not with having to fit the bairn in the back - that's what we have an Accord for.

Guess I'd better go and check whether it is the pressure switch that's causing my a/c not to work, eh? Everything else in the a/c/ system seems to be functioning, just haven't got round to removing splash pan / cooling panel to access the switch yet.