Infuriating 405 air conditioning issue

[carlo14]

Hi all.

Could anyone shed any light on what might be happening here.

I have an erratic and very annoying problem with my 405 2.0 petrol's air conditioning, especially annoying as it is my daily driver! It is a 1995 Mk II automatic.

Basically it works some of the time, not others, and has been going on for about a year. It may work fine for a few days, or more likely work fine for half an hour then just stop working. The A/C light on the heater control comes on and stays on. It has been gassed last Autumn but that made no difference; sometimes it worked sometimes it didn't. When it works it is ice cold and can work for the full hour or so I use it, and then the next day or so. More probably it will work for a few minutes then cut out, and then quite possibly cut back in again a few minutes later (or not). Sometimes it won't work for days. I did find sometimes if I gave the revs a blast it would kick in, but that doesn't work all the time. You can clearly hear the compressor cut in when it works, and remain silent when it doesn't. It has been with two specialists on more than one occasion, once I left it there for a week, and of course behaved it perfectly then.

The heater fan and cooling fans work fine.

Any ideas/troubleshooting I could try?

Cheers!

[RichardW]

By the sound of it the compressor clutch is not working - either this is a fault with the clutch, or it's an electrical feed fault. I would rig up an LED across the compressor contacts, then when it plays up you can see whether the power is there to pull the clutch in or missing. This will then give you a pointer whether you need to look at wiring, or if it's an issue with the clutch itself.

[GiveMeABreak]

Second that ^ The clutch component of the compressor can wear over time and to be honest, at nearly 30 years old if on the original, that's not bad going. I needed a new compressor at only 7 years old.

[carlo14]

Thank you for those, that sounds very plausible.

[ozvtr]

A common problem is the metal friction surfaces of the clutch plates wearing away. The clutch electromagnet can only pull the two plates together from a very small distance. Once the plate surfaces wear by a small amount this distance becomes too great for the electromagnet to work. This is a gradual process and causes the compressor clutch to fail at random times but tends to get worse and worse over time.
There are shims on the input shaft to set the gap of the plates. Typically they look like very thin washers. If that is the problem, the plate gap can be re-shimmed very simply.

[carlo14]

Just an update and a further plea for any help!

I have spent £ hundreds and several months trying to fix this 405 A/C issue (yes I know I'm mad but that's not important right now). It has had a new compressor, pump, drier (?) and pressure switch. Appartently an electrical fault was cleared too. Car also had a new heater matrix last year. Despite all this hardware being fitted along with the recharge it is exactly the same; works fine sometime (usually when engine is cold), than cuts out after a while often when at speed. Latest idea was to fit a different relay and Bitron unit under the headlamp - all to no avail.

It seems to have beaten the best brains at A/C specialists around me. If not any suggestions anyone know a very decent specialist in the South West?

This will not beat me.

[MattBLancs]

Did you try the LED suggestion above?

Compressor= pump so not sure if another component meant in that list?

Presume new compressor included new clutch pulley, so that points more to wiring issue (that the LED could have told you)

Matt

[CitroJim]

It may be one of the temperature sensors giving an intermittently false reading and thus not allowing the A/C to operate... A prime suspect might be the evaporator temperature sensor... If it thinks it's too cold, even though it isn't, the A/C will not start or will shut down. This is to prevent the risk of it icing up...

I know on Citroens of that era the A/C system can be comprehensively investigated using the diagnostic equipments then available... Not being so hot on the Peugeot side of the family I don't know if this is the case for an S2 405 but I would think it might be... A diagnostic session by a knowledgeable operator may well save hours/days/weeks of guesswork...

I can fully understand why you run a 405 as your daily... I had two back in the early 00s and still believe that along with the 205 they were the very best cars Pug ever made

[xantia_v6]

I don't know the details of the control system of the 405, but on some PSA cars of the era, an over-pressure condition shuts off the whole system. So check that the over-pressure switch is not triggering.

[carlo14]

Cheers for the suggestions.

^ CitroJim; are the temperature sensors you mention those in the thermostat/cylinder head housing?

[CitroJim]

^ CitroJim; are the temperature sensors you mention those in the thermostat/cylinder head housing?

No, thy will be in the heater box...

[liquidhandwash]

The last AC problem I had, turned out to be the harmonic balancer spinning on the rubber insert. The rubber fell out and the cam belt ate it, and it all ended very badly.

[CitroJim]

The last AC problem I had, turned out to be the harmonic balancer spinning on the rubber insert.

I've known that happen on a V6 Xantia... Happily the rubber stayed put but the outer would spin very freely whilst the inner stood still!

Usually, the pulley gives ample warning that it's failing by screaming and screeching when a heavy load, such as the A/C compressor or a an alternator charging a low battery, is applied...

[MattBLancs]

The last AC problem I had, turned out to be the harmonic balancer spinning on the rubber insert.

I've known that happen on a V6 Xantia... Happily the rubber stayed put but the outer would spin very freely whilst the inner stood still!

Usually, the pulley gives ample warning that it's failing by screaming and screeching when a heavy load, such as the A/C compressor or a an alternator charging a low battery, is applied...

Less severe (as in not actually staying stationary!) But similar effect noted on the V6 coupes - in that instance I think is normally power steering pump that puts enough load on. Many auxiliary belts changed with no improvement unless someone worked out what going on. Is normally just like belt squeal noise. Tends to get better as engine warms up (expansion appears to tighten grip on the rubber in the pulley)


Test is (engine stopped!) Paint / pen / chalk line across the pulley. Run engine and listen for the squeal. Stop engine and see if the drawn line has a break in it.

Matt

[carlo14]

The exchanger sensors were apparently checked by my man who reckoned they were OK.
We have noticed that next to teh Bitron control unit near the n/s/f headlight is another housing with what looks like a circuit board and 2 relays in it and a multipin connector (a bit like the Bitron one). I'm wondering if this is anything to do with the A/C; it looks corroded and the housing is broken. I shal try and post a picture later.