Had my air con regassed todayand when the garage ame to test it, it was not kicking in..they checked all relays,fuses etc ans the switch itself all ok.they put a live feed to the unit and it worked fine...So apart from a lose wire ,is there any other part that it could be thats prone to giving up or is it just start at the switch and work though the wiring???

id start by seeing if you got a live at the switch when its on

thank you,yes they say the switch is working ...it lights up so power is going to it....have read wher it could br the 3 way pressure switch but can not find a pic to show where its located??

The switch is located next to the aircon dryer, just to the rear nearside of the front bumper. Have to get underneath to see it.

Hello Rob,

The low pressure switch does not drive the clutch, it drives the clutch relay, and the relay energises the clutch.

The garage checked the relays/fuses etc but could not find a fault but when they energise the clutch the aircon is ok.

So they did not have an electrician to follow the voltage trail to the clutch and see where it failed? Hmmmn!

For a cct similar to your system look for the Hi defintion PDF on this link

Rover SD1 CCOT Air Conditioning

You will find a better/actual cct in your workshop manual.

Follow the cct from the low pressure switch 910) to the relay (12) and beyond to the compressor clutch (5) and see where the voltage supply from fuse (C1) is choked off.

and check all the relay and fuse contacts/connectors, often the main source of probs.

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

thank you i will pass your info ...on to those who know so they can have a look...thanks again.

Take the pump off and weigh it in for scrap, open your windows and let the wind flow in, job done.
Air con is for puffs.

can we assume it is still gassed? has this been checked? putting a live feed to the compressor would bypass the low pressure switch would it not and force the compressor to run even if the system is low or even empty?

But Gavin, Surely they should have observed that the hi pressure side would get hot and cool down after the condenser and go super cold after the orifice tube and cold air come out of the vents? Its a pretty motherhood situation for anyone gassing a system, methinks?

Ramon

i would expect so but getting the simple things clear and straight is always the first step. we wouldn't want to miss something silly as can often happen when trying to help poeple/cars we have never seen!!

Oh! I agree 100% Gavin, not to overlook the possibility suggested, particularly as some service agents exemplify in rip-off mode. It just boggles the mind that it would be otherwise so obvious.

I do understand what you are saying... however i have worked with and known the owners and the people who are testing it and they did do a comprehensive search of all the obvious thing ..relays fuses pipes getting hot/cold and th dash switch,but they only had a small bit of time so they are going to do a more indepth search on tues...just wonderd if there was any common failures giving this prob?

Bit confused, garage said air con not working even though just had it re gassed.. tried it today and on LOW it feels very cold through the vents,also when i switch it off the air con light flashes (as it should when set on LOW) however can not hear any fans kicking in or anything..is that right giving the cold weather.. also windscreen demists very fast when ...i think i have turned it on?

you will have to feel the pipes from the compressor and check the clutch has engaged i think

Some aircon systems will not kick in if the ambient temp outside is too low ( i know bmw's wouldnt work below 5 degrees) which confuses the hell out of the owners who dont know about these things, might be worth checking out the operating specs on the a/con before you go ripping it to bits. JMHO

rob evans said:

Bit confused, garage said air con not working even though just had it re gassed.. tried it today and on LOW it feels very cold through the vents,also when i switch it off the air con light flashes (as it should when set on LOW) however can not hear any fans kicking in or anything..is that right giving the cold weather.. also windscreen demists very fast when ...i think i have turned it on?

Click to expand...

Hello Rob, With the engine idling, the A/C switched on and you standing near the open engine bay you will be able to hear if the clutch is engaging and the compressor kicks in under the control of the prior mentioned switch. If working normally this cycles at approx 3 on/offs per minute.

If/When that happens, the compressor will compress and its output pipe gets warm/hot, the gasses circulate through the system, the condenser in front of the rad gives up its heat and the gasses cool, so you will be able to sense the heat changes with your hand on the input/output condenser pipes.

Further round the system is an orifice tube which rapidly decompresses the gas and the pipes thereabout go super cold even freezing any surface moisture.

The very cold gas goes thro the evaporator where it absorbs cabin heat and then on to the accumulator c/w low pressure switch, where this description started'

If none of that is happening then the compressor may not be engaging because of low gas or a fault condition.

By shorting out the afore-mentioned switch that you have identified, the compressor will kick in and stay kicked in, so dont leave it on too long - in case there is low gas.

The heat circumstances described above should occur and you will be able to detect the effects mentioned.

If there is gas and the system appears to be working, try emulating the cycle with your short circuited switch, 10 sec on, 10 secs off, repeated, and see if the A/C process works.

If it does then there would appear to be a switch problem, or some other control fault.

If it does not then the gassing is probably low and you can proceed no further until regassed.

The above little sequence is quite simple and involves only a jump lead across those switch contacts. Just a dab to start with and gradually progress.

Dont start until you understand what I am suggesting and if you are not confident, then dont start - just pass the suggestions to your experts for their evaluation.

Ramon

The condenser fans will not cut in when the weather is cold-only when the outside temperature is hot-this is quite normal. My fans rarely cut in, even in hot weather and the air from the vents is freezing on "Lo"-even during the hottest weather.

thank you all for your help,have been back to garage today and as i said i think it's working it is,they asked me to put air con on as they watched the clutch and yes worked straight away...they did not know that light on was air con OFF.

P38's are like that-the light on the switch is ON when the aircon is OFF !!!!!