No power to the compressor!

davetherave · Unread post by **davetherave** » 18 Jun 2009, 14:25

Having had a word with Jim at the dsm rally regarding the air con or lack of, he suggested that before i rather drastically removed the compressor i check if any power was getting to the clutch.

Having just been under it and tested it, there is not a sausage! so maybe it can be salvaged after all!

I will update later....

Unread post by **CitroJim** » 18 Jun 2009, 21:27

Hi Dave,

This is the circuit of the MK2 aircon system and the compressor clutch is item 8020.

It should help track it down. If you need the harness diagram, let me know...

davetherave · Unread post by **davetherave** » 19 Jun 2009, 13:30

Thanks Jim, ive been out and chased wires etc. there is no break in the wire to the relay, so i suspect that the relay may be at fault.

Is there a way to bypass the sensor that detects if there is gas in the system just to double check there hasnt been a massive leak?
Thanks Dave

davetherave · Unread post by **davetherave** » 19 Jun 2009, 14:09

Just phoned local dealers. they wanted 15 quid for a relay! Looks like a trip to the scrapyard will be in order!

Unread post by **admiral51** » 19 Jun 2009, 20:59

Hi Dave
Not sure what series your Xantia is but on a MK1 if you pull off the plug on the reciever/dryer you can short the pins to do one of 2 things but i cant remember which 2 pins do what

From memory there should be 4 wires going into the now unplugged plug 2 thick wires 2 thin wires.By bridgeing the 2 corresponding wires with the engine running 1 set will put both cooling fans spinning at full speed this is the default for high pressure in the system.Bridgeing the other set will bypass the low pressure switch for the compressor and will engage the compressor clutch

If you do get the clutch to kick in dont leave it running for more than a couple of seconds as this will cause damage to the system

I did a post quite a while back on this subject and Clogzz and Alan S were extremely helpful. Will have a look and see if i can find it

Colin

Unread post by **admiral51** » 19 Jun 2009, 21:17

Not so much a topic on A/C more of one on removing bumpers and radiators no wonder i couldnt find it in A/C section

Its definitely the 2 thick wires that need to have the pins bridged to bypass the HP/LP switch

I had the engine running A/C button on and interior blower on when i did the bridging test to make sure all the other pre requisites (sp?) had been met

HTH

Colin

davetherave · Unread post by **davetherave** » 19 Jun 2009, 21:20

Cheers Colin!

I think the switch must be fine, as the fans power up full speed ahead when its turned on, so hopefully just a knackered relay!

Unread post by **admiral51** » 19 Jun 2009, 22:53

davetherave wrote:
I think the switch must be fine, as the fans power up full speed ahead when its turned on, so hopefully just a knackered relay!

Hi dave
That is setting alarm bells ringing

Dont take this as gospel but this is how i understand the system to work
1.Everything is controlled by the information sent/recieved by the Bitron sensor
2.The A/C needs the following things to be inplace before it will start
3.The A/C button must be switched to the on position
4.The interior fan must be switched on/auto
4a.Caviat on MK2 cars if the interior slider is set to demist screen then the A/C will switch on
5.Both fans must run at slow speed.Bitron sensor cannot tell if fans are actually running it only knows if power has been succesfully applied to them
6.Power is then sent to HP/LP switch
7.If HP if detected then both fans are set to full speed and A/C disabled until HP is no longer present
8.LP in system will prevent compressor from engaging

If as you say both fans go high speed when you engage the A/C then i would point the blame at the switch as this is saying the system is under HP even though it hasnt started.
Try starting the A/C with the pressure switch plug disconnected and see what happens to the fans.The compressor shouldnt kick in as the Bitron is not recieving any information from the HP/LP switch so cant commit to doing anything other than starting the fans at slow speed something it should do before it sends power to the HP/LP switch.

You should (hopefully

) find that the fans spin at slow speed and you will then be able to bridge the 2 thick wires in the plug to engage the compressor clutch.
If the fans spins at full speed with the plug pulled then i would suspect a wiring fault/short to ground in the thin wires leading to plug

Hope this sort of helps

Colin

PS If it is the switch i think i have a good spare i can pop in the post to you FOC

davetherave · Unread post by **davetherave** » 20 Jun 2009, 08:19

I see...
I will have a run through those today, it could be that the fans are at low speed as i have only observed them at one speed and presumed it to be high, i will post back later....

davetherave · Unread post by **davetherave** » 20 Jun 2009, 10:06

Right, i took the sensor connector off of the dryer bottle (by the way the fans engage at a slow speed upon engaging the system not high as previously said!)

I then bridged the two thick wires and the clutch engaged!!!
However it was making one hell of a noise and sounded like it wanted to blow up.

So im thinking i should take it to quick fit where it was very recently regassed and get them to pressure check it, does this sound sensible?

Or choice 2 sod the stupid air con and open the windows!

davetherave · Unread post by **davetherave** » 20 Jun 2009, 12:18

Next update is much more positive, i decided that the compressor or a bearing or some part of it must be knackered, as that was way to much noise!

So i went down to the scrappy ( I love scrap yards far too much) 5 mins away after ringing and asking if they had any xantias or 406's, he said no xantias but he did have a 406!

The 406 had the right compressor which he confirmed was working as he "enviromentally correctly" disposed of the gas! Also there was a xantia which he thought was a bx! with the right part again!

So if anyone wants any bits bringing to the ccc national from a v reg silver hdi xantia let me no- it looked in very good nick and the interior was immaculate!

Anyway i got the compressor for a measley £10, because he was part time and wasnt bothered!

Unread post by **CitroJim** » 20 Jun 2009, 21:53

Shame the compressor is not healthy after all that Dave

Still, at least you've sourced one

Colin, you're rapidly turning into our aircon specialist

8)

Unread post by **admiral51** » 20 Jun 2009, 22:30

Hi Dave
Glad to see the problem has been identified

£10 for a compressor 8) 8)

CitroJim wrote:
Colin, you're rapidly turning into our aircon specialist 8)

I think in this age of litigation i would be hauled up before the Judge and have to plead guilty to charges of plagiarism

All the information i know about Aircon on the Xantia i have gleaned from the good people on this Forum

Just put it all together in one post

Colin

davetherave · Unread post by **davetherave** » 20 Jun 2009, 22:34

Its good to have people with the knowledge though! Even if it is second hand!

Unread post by **admiral51** » 21 Jun 2009, 02:19

Hi Dave
I know this a late night/earlry morning post but something doesnt add up so if this seems a bit wayward i apologise in advence

I have re read your blog and this thread and you say that the system has been recently been regassed but at no stage have you said the aircon was working

When i tested my compressor by bridging the 2 thick wires i was concerned that the compressor was very quite and Alan S replied that this was because it was not under load (ie system empty of gas) but i would expect to hear/notice a drop in engine revs at idle once the system was full of gas and running ok.
The more i think about it (thinking is a problem for me ..gives me a headache

) the HP/LP switch is not at fault its actually doing what it should.The HP side of it is designed to put the fans at high speed and cut the compressor when the system has actually been running not stop it starting(could be wrong here just my logic

)
The LP side of the switch is there to stop the system starting and thereby causing damage.As we have proved that bypassing the switch you can get the compressor to engage then power is being fed to both the switch and the compressor as it should be so maybe the problem is actually a LP one ie you have a major leak if the system has recently been regassed.
I agree with the diagnosise that the compressor could be knackered due to the noise it makes but as far as the bitron sending power to it to engage then this has nothing to do with the condition of the compressor as all the bitron does is tick the boxes and commit the power.The bitron has no knowledge of the condition of the compressor all it knows is boxes A-B-C-D etc are ok so flick the switch

If there is no power at the compressor then the HP/LP switch is deciding to send a signal that it has detected a problem and it is refusing to allow power to be sent to the compressor

It could be worth a visit back to where it was recently regassed to do a pressure/leak test as a small leak should enable the system to start but a major one will cause all sorts of grief

Hope some of this makes sense

Colin