406 aircon problem. Wiring diagram anyone?

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gareth_purves
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406 aircon problem. Wiring diagram anyone?

Post by gareth_purves » 16 Jul 2006, 11:16

my aircon has packed up on my R reg 406 turbo diesel. i have a very good understanding of all things car related but these have generally been older cars and this is my first car with aircon. the haynes manual is less than useless so now i find myself here!

the symptoms are as follows:
~ the switch lights up when pressed.
~ all fuses are ok
~ the pump doesn't appear to engage. (end plate never spins)
~ there is plenty of refrigerant (too much if anything, i've used a gauge on it as i thought it might need recharging.)

one thing that happened that may be related is that the re-circulation flap servo packed up. this has now been pulled out and the flap manually set to pull air in from the outside. i suspect this doesn't have any bearing on things but i have no wiring to reference!

does anyone have any form of wiring diagram for this? i can't find anything on the web or manuals...

any ideas?
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Post by Clogzz » 16 Jul 2006, 14:29

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Post by gareth_purves » 16 Jul 2006, 16:55

thanks for that mate.

here's hoping the 306 and xantia is the same as the 406... that 306 wiring diagram looks like it'll help understand the control systems on the aircon anyway.

i've not yet checked what the cooling fans are doing but it's really hot here and it doesn't overheat! i'll look further next time it's up to temperature.

can the cooling fans stop the aircon powering up?
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Post by Clogzz » 17 Jul 2006, 13:59

No, the fans can’t prevent the aircon from operating because there’s nothing to sense what the fans are doing.
Most fan faults are in the relays, wiring and motors, and the only sensing that can be derived from the lack of fan operation is lack of cooling of the condenser.
That may cause a rise of pressure in the aircon, which in turn would be sensed by the pressure sensor switch on the dryer bottle, to release the compressor clutch.
That’s for when the car is moving slowly, because at speed the incoming breeze is more than enough to cool the condenser.
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Post by gareth_purves » 17 Jul 2006, 21:55

that makes sense. i assumed it would have an overheat/overpressure cutout but being french i thought it could include faults on the fans! you never know with french cars! :D
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Post by KennyW » 18 Jul 2006, 12:44

Hi Gareth,

I've had similair problems which I have since recitfied , Clogzz's has post my LONG thread about it on your post.

My fans area running as per diagrams but A/C is not.

All the best

Kenny W
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Post by gareth_purves » 20 Jul 2006, 21:52

i had a bit of a play yesterday...

there was no power going to the aircon pump so i routed a positive feed and an earth to it and hey presto, chilly air!!! :D

hardly a long term solution though.

still not a lot further with faultfinding though... i'm thinking of popping into my local peugeot dealers to see if they can print me off a wiring diagram for the 406... unlikely but it's got to be worth asking!
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Post by alan s » 21 Jul 2006, 01:55

It sounds as though the HP/LP switch on top of the receiver/dryer next to the sight glass with a brown plug with 4 (or possibly 5) wires going to it is shot.
If this is the problem, a new one can be fitted DIY quite easily.
You will see a hex head between the receiver and the body of the switch that takes about a 12mm open ender from memory. Disconnect the plug, screw this out and screw new one in.
Check to see if it comes with a new "O" ring and if not, renew the "O" ring.
Inside the fitting it screws into, iy has a schraeder valve (same as you get on a car tyre) and it seals the system as you screw it out, so there's no reason to need to take it to an air con repairer to do the job.


Alan S
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Post by gareth_purves » 21 Jul 2006, 08:10

cheers mate! :D

any ideas on cost?

oh, under what conditions would this cut the system out? if there's a fault in the system rather than the switch it could be working correctly? :?
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Post by alan s » 21 Jul 2006, 09:03

There's two ways it can stop it.
HP = High Pressure

LP = Low Pressure

So if for any reason (blocked receiver dryer, blocked TX valve, overcharged with gas, air got into the system when charging, fans stopped operating) and the head pressure exceeds the limit allowed by the switch, which is a safety device, it will cut the power to the compressor.

Low pressure if the system is short of or out of gas.

Testing switch as being the cause is usually just a case of bridging the two heavy gauge wires at the plug.
Cost I would imagine at around 30 quid.
Here's a thread where a similar problem as yours was discussed and I'd imagine the system on a 406 would be as close as dammit is to swearing.

http://www.frenchcarforum.co.uk/forum/v ... 6&start=60

Hope that helps you sort it.



Alan S
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Post by gareth_purves » 21 Jul 2006, 13:39

alan s wrote:There's two ways it can stop it.
HP = High Pressure

LP = Low Pressure


high pressure....... when i tested for gas pressure on my gauge, it was into the red, i'll have to check what pressure this is though. seems odd that it would have increased to stop the system without adding more gas though. :?

what are the upper and lower pressure limits?
do i need the system running to check pressures or just sat still?
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Post by alan s » 21 Jul 2006, 23:20

OK mate, I'll give you a quick crash course in refrigeration. I'll keep it in laymans terms as much as possible for the benefit of anyone else who may need the info in the future.

For safety's sake, connect gauges with the engine stopped.
Colour codes for gauges are usually blue for compound gauge and red for head gauge.

Connect compound to fitting marked "S" (suction) and head gauge to "D" (discharge).
Pressures should be almost identical due to "balancing" or "equalisation" of pressures and the reading will vary depending on the ambient temperatures.

Start engine and get the engine held by someone else at around 1500rpm.

The gauges should decrease on the suction side and increase on the head side of things.
Again, the readings will vary according to operating loads but as a rule of thumb, around 200 psi head and 6 psi suction after a couple of minutes would be acceptable.
The HP/LP switches should have their operating specs marked on the outside, but if the gauge were to go into vacuum, that is when the LP side would drop out and if it were to exceed say = to 300+ psi, the HP would drop out.
If you were to get a situation where say the compound gauge on the suction side were to go into vacuum and the head gauge show say 300 psi, then it would be safe to say the dehydrating medium in the receiver/dryer has collapsed and had blocked the system possibly at the filter. If it were to run OK and suddenly the aforementioned symptoms were to surface, it would be possibly moisture in the system.
If the both gauges are below what they should be (say head at 70 - 100 psi; suction into vacuum) then it would be safe to say low on gas.
Normally (based on old R12 readings) it would go around 5/6 psi and head around 130/160 after a couple of minutes and as the suction pressure dropped, the head will increase for a while but begin to drop back as the load is dispersed. It has to be remembered also that the fans alone only give a partial amount of air passing over the condensor and that the load is dissipated much more when the car is in motion, so it will always pull pressures back further along with the reduction in temperature once the car itself is in motion, so a certain amount of the work has to be done bearing this in mind.

Hope you can follow that; if not just ask anything you're not certain of.


Alan S
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She said "Put the cat out" She didn't mention it was on fire!!

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Post by gareth_purves » 23 Jul 2006, 11:19

cheers mate. that all seems to make sense. the pressure gauge i have will only fit on one place though (as far as i can see).

i assume id need a 'proper' refilling setup to do this properly?
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Post by alan s » 23 Jul 2006, 19:29

If the gauge you have has numbers below as well as above 0 (Zero) it will be a compound gauge which is only meant for the suction side.
AS far as fittings go, there will definitely be two places they can fit which are commonly on the back of the actual compressor, however it's not uncommon in some cases to have one actually teed into one of the lines. If you examin the area around where the fitting is on the compressor where the fitting is, you should find it stamped with either a D or an S. Once you establish this, you can then trace the other line and should find the other fitting on it somewhere.


Alan S
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RIP Sept 19th 2008.

She said "Put the cat out" She didn't mention it was on fire!!