Aircon question

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velosolex50
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Aircon question

Post by velosolex50 » Fri May 19, 2006 9:36 pm

Hello all
My new pride and joy is almost perfect except for the aircon only working intermittently. The dash switch was missing, and has been replaced with a toggle switch. Most times, the switch doesn't do anything, but when it's feeling co-operative, the compressor clutch clicks in & it works fine for a while.
On the basis that the pressure might be low & operating the low pressure cut out swith, I had a a/c guy check it and he topped it up with about 200gm of r21 (apparently a drop in replacement for r12) as it was a bit low. It worked fine for an hour or two, then went back to how it was before. Obviously there cant be a significant leak, or it wouldn't work at all. I guess a possibility would be moisture in the system, which would be easily fixed with a pump out, but unfortunately the a/c guy doesn't have r12 recovery gear. I also measured the voltage across the terminals of the switch, and was surprised to find it was only 6v, so I suspect a problem with the switch arrangement, but there is no wiring diagram in the haynes, so it is tricky to sort out.
Anyone got any ideas? Suggestions gratefully received- (but not necessarily acted on!!)
Regards
Huw

AlanS
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Post by AlanS » Fri May 19, 2006 10:13 pm

Both me and my computer are pretty sick at present so I have to take the easy option.

Take a peak at this:

http://www.aussiefrogs.com/forum/showthread.php?t=9161


Alan S
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velosolex50
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Post by velosolex50 » Fri May 19, 2006 10:58 pm

Thanks Alan, will do.

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Philip Chidlow
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Post by Philip Chidlow » Fri May 19, 2006 11:26 pm

My air con chap put something called RS24 in my BX's a/c.
• COMING SOON... 1992 Citroen BX TZD Turbo Hurricane
• COMING SOON... 1998 Citroen Xantia 2.0 16v auto Exclusive
• Xsara Picasso 1.6 16v
and some Ford tat lol

ernst stavro blofeld
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Post by ernst stavro blofeld » Sat May 20, 2006 6:28 pm

The dash switch, assuming that this is a phase 2 car is a 10K Ohm variable resistor. Replacing this with a switch will give an all or nothing response. I'm not at all clear about where you are getting six volts. Is this across the dash switch or the LP switch?

In normal operation, the compressor will always cut in on switch on if there is sufficient fluid in the system. The need for a second top up in a few days certainly indicates a serious leak and you would be well advised to have a competent a/c man check it all out with a leak detection dye. Remove the glovebox and the cover on the end of the heater (three screws) before he comes to save him time and effort. If the copper pipes you'll find here are oily, then the TX valve will probably be the source of your leak in which case, you should think of doing a full R134a retrofit which will cost a little time and money (Think £100 and a weekend) but will in return provide you with one of the automotive world's greatest aircon rigs so it is well worth persevering with. Be warned though; it has to be done properly or you'll be throwing money in great and regular chunks at a system that will never work right. Feel free to pm with questions.

velosolex50
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Post by velosolex50 » Sun May 21, 2006 11:06 pm

Hi
the 6v is across the black & black/white striped wires hanging out through the slot that should house the A/C slide switch on the upper left of the centre console. Not exactly sure what they are connected to, wires disappear into the depths behind the ash tray. Odd that bridging them makes it work sometimes, but not often, and the compressor only runs for a short time (10 - 30 seconds) before clicking off again. System pressure apparently ok.
The post that AlanS kindly referred me to mentions an electronic control unit behind the door open panel, but I can't see anything there on my car, unless they meant deeper in. Not to keen on breaking the dash with possibly unnecessary dismantling just yet. Sounds as though I should try to source a suitable variable resistor and try it first.
Thanks all for your help, I will let you know how it goes.
Huw

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Post by AlanS » Mon May 22, 2006 1:29 am

Remember this part that Ken had in his write up?
Reverse-Engineering: The control module is electronic and the sensor wire come from the module which is behind the dorr open display panel and goes up the right side of the air box disappearing into the air box beside the coolant pipes going to the heater element.
From memory, if you pull out the ashtray and coin box etc, and slacken the screws off that retain that section, it will pull out enough to give some access without creating major problems and also allows space to shine spotloghts and things so things can be identified.
Once you identify the two wires Ken speaks of, pull any slack back out that might be there engine side of the firewall, back into the cabin. Cut the two wires just before where they go into the cover to the matrix/evaporator (leaving enough to reconnect in case you've got the worng ones :wink: ) and bare the ends. To test if they're the correct ones, just switch on the ignition and try to start the air/con; it shouldn't start. Then tap the two bared ends together and it should all kick over; condensor fans and compressor; that proves you've got the correct wires.
IIRC, the wires need to be pushed across from one side of the dash to the other, so if I'm correct, a piece of plastic coated wire was ised to bind them to, push through the underdash wiring maze and pulled through from the other side.
Raise the bonnet and remove that black plate that sits in front of the windscreen as well as the air scittle grille that is between the windscreen and bonnet. You will find the top of the evaporator cover down there. Remove it also. From here, you will see the evaporator and if you can work out a place that will give access, get someone (or you) inside the car to carefully poke a small hole through the plastic. We used a screwdriver with a blade about 3/16". We did this to avoid risks involved with using a drill.
Solder extra long pigtails onto the variable resistor and put it into position by jamming it in between the alloy fins in the evaporator. Some do use a dob of silicone sealant to hold in firm although I found that I could bend the alloy fins in tight enough to work efficiently. Cut and solder the wires from behind the dash onto the extended pigtails at a suitable length and insitu. Refit the top of the evaporator cover and then start up the car and turn the air/con on. Start off using the slide control at its warmest setting and see if it cools and then switches off, then move it further to the right and the temp should get progressively cooler and switch off. If you find it gets too cold, move the resistor upwards and reposition in the fins and if not cold enough, go downwards. If it stays switched off for too long, you've gone too high on the coil and if it runs too long and gets too cold then loses its cooling for too long, you've gone too low. I found around 1/4 - 1/3rd way down to be ideal.
Beauty of this is that if in future you need to replace it again, where Mr Citroens idea takes about 5 hours to achieve (dash out etc) this is about 10 - 15 minutes. As a bonus, the cars we've done so far have absolutely brilliant temperature control due to the minute adjustments to temperature that can be made using the slide control on the dash.
Hope that description is comprehendable enough to follow; if not, you know where I am.


Alan S
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ernst stavro blofeld
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Post by ernst stavro blofeld » Mon May 22, 2006 8:48 am

Thanks as usual Alan. Just to clarify, the two wires hanging out of the dash should go to the 10K variable resistor. Six volts between them is correct. Removing the glovebox and evaporator cover is straightforward and there is little risk of breaking anything. Screws top and bottom of the glovebox aperture come out and glovebox slides out. We all do this when electrical debugging is necessary because you can get to all the wiring! Three screws with either 7 or 8mm heads come out to remove the evap cover.

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Post by mat_fenwick » Mon May 22, 2006 12:57 pm

This sounds similar to my question I was about to ask!

Finally got the air con transferred from a scrap car and working, after 9 months of work (but that did include getting married, new job, renovating a house and moving house twice...). My question is:
It seems to be cycling on and off at approx 30 second intervals – is this normal?

The slider control for the air con is fully over to the right – I had assumed that this position should run the compressor 100% of the time. I have not yet tried it in temperatures above 15.C (or when it is not raining), as we haven’t been that fortunate here yet since I had it charged (with RS24). When the clutch is engaged the air is cold, and still remains almost as cold during the 'off' period, so in terms of cooling ability it probably doesn't matter, just wondered if it was normal.

From the sound of things I may be able to change the cycling time by moving a temperature sensitive resistor closer or further away from the evaporator?

Also, will the current drawn by the rad fans decrease as you are moving along? I would imagine that the airflow would help rotate them.

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Post by tom » Mon May 22, 2006 2:32 pm

The current drawn by the rad fans will not be significantly affected by forward speed. There is a lot of ironmongery behind them. THe system should cycle. The compressor will cut in and out, the duty cycle being normally adjusted by the control pot. 30 seconds on and 30 seconds off seems a little quick to me but I have an r134a system which behaves differently. I would suggest that you measure the vent temperature and assess how much cooling you are getting. A BX will chill incoming air by 20 degrees C if it is in good order, without any trouble on a warm day. Usually, the compressor will cut in just as you start to think that it isn't blowing quite as cold as it was a minute ago. If it is doing that then you are probably all right!

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Post by mat_fenwick » Mon May 22, 2006 3:09 pm

Thanks Tom,

Your advice and that from AlanS was very helpful during the installation. I am guessing around 30 seconds cycle time but as you say, just when I can feel the temperature increase, it kicks back in again.
I was slightly worried that this cycle time would not be enough in hotter weather (off to France in 2 weeks) but am I right in thinking that the cycle time would change depending on the air temperature?
(Vent temp was measured at about 7.C, on a coolish day - about 15.C)

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Post by AlanS » Mon May 22, 2006 9:00 pm

7 is a bit high; it should be around 4 where it comes from the vent.
Check that the circulaion fan is operating as it should, as we found similar symptoms caused by it blowing cold air over the sensor rather than drawing it over.

Alan S
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velosolex50
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Post by velosolex50 » Mon May 22, 2006 11:49 pm

What a bunch of helpful folk you all are! I will follow the suggestions when I get the chance.
Huw

tim leech

Post by tim leech » Tue May 23, 2006 9:15 am

I have a spare black fascia panel for a aircon vehicle with the a/c slider switch and air recirculation feature if that helps at all?

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Post by mat_fenwick » Wed May 24, 2006 1:00 pm

tim leech wrote:I have a spare black fascia panel for a aircon vehicle with the a/c slider switch and air recirculation feature if that helps at all?
There were times during the installation where I thought about just fitting the fascia panel and pretending about the air con!

Alan, do you mean the twin blower fans? From memory (don't have your write up to hand) didn't you have a situation where one fan was wired the other way round? Both mine are blowing as they should be.

After reading the other recent post on the board, my system may be icing up as I have only measured the temperature at the vent with it drawing in fresh (read cold and wet) air.

I am guessing that the coldest air will be achieved with forward motion and the control on recirculate?

One last thing - a plug for http://www.ariazone.co.uk/ who sourced me a condenser when most places didn't even list it. It arrived from France within a few days.