A/C wiring diagrams or fault finding help pls.

[brian j 32]

Hi. 
my ph2 has factory A/C. Before it was laid up this had been converted to r134a gas with a new pressure switch, receiver/dryer and condensor and worked fine. 
 

now it does not work. In summary:
There is gas (just vacuum tested and regassed)

the switch lights up

the compressor gets no power. 

i have tried a new pressure switch which made no difference.

 

does anyone have a wiring diagram so I can start tracing the fault? Or any go to places to check? 
 

thanks. 
brian

[SRDT 175]

1989 models:

 

1991 models

[brian j 32]

Awesome. Thanks @SRDT!  I love this community.

 

 

[brian j 32]

@SRDT - follow up:  I can get a lot of it, but do you have access to the key for the 1990 onward diagrams?  If not I can work it out by tracing wires, but knowing what some of the more obscure parts are (even in French) would be helpful. 

[SRDT 175]

Here:

http://www.dethomaso.fr/2019/02/schemas-electriques-205.html

 

309 diagrams are also pretty similar, the fuse box and most of the A/C components are the same.

http://www.dethomaso.fr/2019/02/schemas-electriques-309.html

[brian j 32]

I have waded my way through and I am getting somewhere but I could do with some input to progress…

 

after fixing some corroded wiring, I can now cycle the compressor from the pressure switch by powering pin 1 with a power probe, and I have proven that radiator fans are fine, idle solenoid is fine, compressor is fine. 
 

when I press the switch, it illuminates, but there is no power to the idle solenoid or to pin1 of the pressure switch. 
 

I think this means I either have:

 

- more duff wiring

- a faulty switch ( if it illuminates it should work tho)

- a faulty ‘electronic thermostat’ unit

- a faulty thermistor in the heater box. 
 

does anyone know where the ‘thermostat electronique’ is located?

Also what the resistance values for the thermistor should be? 

[SRDT 175]

I can't remember exactly where it was. It should be near, or even on, the heater box under the dash.

the H on H893 ba means Habitacle so it's inside the cabin at least.

[brian j 32]

Sadly the switch works fine so it is under dash wiring, the electronic thermostat or the thermistor. 
 

I think I have ground the thermostat bolted to the bottom of the heater box. Just waiting for some radio removal keys to arrive so I can try and get to it. 
 

[brian j 32]

I have now been through all of the wiring and every link in the chain checks out.

 

that means the fault is either the ‘electronic thermostat’ unit or the temperature probe on the evaporator.  
 

unfortunately the temperature probe is open circuit so I suspect that is the culprit (sadly because a. I can get a NOS electronic thermostat on eBay for sensible money and b. The temperature probe is inside the heater box.)

 

what I really need is to get a good temperature probe or know its resistance specs so I can test the thermostat unit. 

Does anyone know if I will have to remove the whole heater box to get to it? How evil a job is that? (I figure about as evil as it gets) 

[brian j 32]

I finally bit the bullet and ripped the dash out, so I can deal in certainties here. 

 

The sensor is a thermistor. If I bend the case I could get it to make contact. 

Resistance at room temperature is around 5k ohms. 
In a glass of melting ice it is around 18k ohms.

Research found that the newer Peugeot models use a thermistor with a lower resistance when cold. This is not sufficient to switch the ac off on the 205 when the evaporator is freezing. 

I have fitted a Xsara part (6445HF) which is differently packaged (metal tube not plastic strip) but has similar resistance values.

This appears to work, although I need to get the gas topped up and the dash back together before I can know for sure. 

 

It IS possible to access the sensor without removing the heater box, but only if you have small hands.  With the dash top off, there is space where the air duct for the central vents is to get to it and replace it.  It is possible to feed the leads through by removing the clips and partially splitting the heater box.

 

Being a 205, literally every pice of the dash proved to be cracked or broken in some way on removal, so there was a day of epoxy and plastic welding to get to this:

 

 

All of the parts did weld up well and have gone in ok though, which is a result.

 

I messed up though.  A quick test before putting the trim back showed that I had no heater fan and the heater controls were not lit.  This led, in turn, to finding the plug dangling loose under the dash. (Doh!!)

 

The plug did not fit up behind the dash, and I was not going to remove it again, so I de-pinned it and pulled the wires through individually before reinstating it at the end.

With a following wind, Friday should see it back together and maybe even working A/C.

 

I hope this is a useful reference for someone in future