A friend has a Dec 1999 Peugeot 406 2.0 HDi. The display on the climate control panel indicates that the A/C is on and functioning, but it doesn't actually work. Thermostat has already been replaced to no effect. Suggestions he's had so far were to replace the control panel or plug some kind of additional "control box" (apparently specifically for the aircon) onto the ECU.
1) Does anyone know is there a proper name or part number for this "control box"?
2) Would replacing the control panel work? From what he's said, I don't think the term "control panel" means the facia on the dash, but some hidden control unit under the bonnet or behind the dash - maybe this is the same as the control unit mentioned above?
3) The compressor works when connected directly to the battery.
Apparently there is sufficient gas that the system doesn't need recharged.
Sorr I can't give any more details - not my car!
andymc
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Does the fan work and blow air out into the cabin?
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If the compressor doesn't come on, there are a number of things to check first, before you condem the ecu.
Firstly, it needs sufficient gas pressure, then you need to check the switch that monitors gas pressure to make sure it's switching and getting power. Then check relays, fuses and wiring to the compressor and pressure switch. Then you'll need to check things such as the ambient temp sensor, engine temp sensor, TPS, sun load sensor. These are hard to check without the tech tool, as they may well be working, but are registering outside the normal range, ie. it thinks the engine is overheating when it isn't.
You say that 'apparently' it has pressure, so you need to be sure and let us know what it is and how it was measured. When you connected the compresor directly, did the a/c get cold?
The climate panel does the controlling, and is called the climate ecu.
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Sorry for not being clearer about this - I'm only reporting what I've been told, I haven't looked at the car and to be honest I wouldn't know what to look for! I'm posting on my friend's behalf, really. He had first of all taken the car to a local Pug dealership, where they plugged in the diagnostic computer and consequently changed the thermostat - with no effect. He then went to an independent mechanic, who recommended changing the control panel. As far as I understand, this meant a control unit behind the dash or under the bonnet rather than the display bit in the dash with buttons or switches for changing fan speed etc. But when a control panel was ordered, it was the dashboard display that arrived (and was returned unused).
BB - as far as I know it does blow air into the cabin, but doesn't cool the air. I'll double-check this.
Dave N - you mention the TPS - does that stand for temperature pressure sender? The step-by-step process outlined above should be very helpful and might help his mechanic to diagnose & fix the problem. I'll pass it on and report any progress back.
Thanks to you both for the responses so far.
andymc
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The system must be out of gas - a very common problem indeed.
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Sorry, TPS is Throttle position sensor.
The control unit is the bit with the display that goes in the dash. I don't think there's another ecu hidden away. But I doubt it's faulty, as it relies on inputs from various other sources, and only switches very low current, all the major switching is done with relays. Not sure what they mean by 'thermostat', as this car has a variable compressor that maintins evaporator temp, so doesn't need a thermostat as such. They could be talking abbout the engine temp sensor or ambient temp sensor. But having changed what they did, and it not fixing it, what did they then think the problem could be? I know I seen faulty refrigerant pressure switches, and I always keep one handy. If you get a wiring diagram they're easy to check.
Unfortunatly, these days you see more and more electrical problem, I guess that's progress for you! Most manufacturers don't list the specs for sensors, or indeed even tell you where they're located. Hardly any make wiring diagrams available, and none stock any of the parts to give a try. Not to mention the £10K computer that will show any fault codes or allow you to check sensor outputs.
I usually spend a short while checking the basics, then send them to a dealer. Simply because the customer won't pay for all the time it takes to go through everything, that's if I even have the correct info available. It just ends up in a bun-fight when you tell the customer you found a busted wire, and it's cost them 4 hours of labour to find it. Let the main dealer have the grief and bad mouthing that usually happens!
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