Air con compressor kicks out on tickover

[Paxman Power]

1996 Xantia 1.9TD Hatch XUD with Bosch pump.

My solution to this problem was based on the fact that there is only one electrical thing directly connected to the throttle - the potentiometer on top of the pump.

I fiddled with this many years ago when trying to get the tickover speed down from permanent fast idle. Had no effect until I understood the purpose of the electrovalves and vacuum system which actually controlled the idle speed. It was only by accident that I discovered that by rotating the potentiomener that the electrovalve activated and the idle speed dropped to normal.

Since that time various vacuum hoses have died and the car runs at fast idle all the time. Will need to sort it some day!

At MOT time last month the car failed on excess emissions. The tester advised running the tank low and putting in a dose of injector cleaner. As the tank was almost full I decided that in order to give it a fighting chance I'd also put injector cleaner directly into the fuel filter. At the same time I also adjusted the potentiometer position. Don't know if this helped, but it went from a figure of 3.02 (Fail) to 0.79 (and a "Fast Pass" at that!).

So when this week I was trying to work out why my aircon wasn't cold I discovered, like you, that the compressor clutch wasn't kicking in at idle and only working when the revs were increased. When it was revved the clutch kicked in and the compressor ran, but only until the revs dropped again and the clutch dropped out. A slow anti-clockwise adjustment of the potentiometer with the engine running and the aircon turned on and all of a sudden the compressor kicked in.

Might be worth looking at it - especially if you have a fast idle issue as well.

[dieseldoggy]

1996 Xantia 1.9TD Hatch XUD with Bosch pump.

My solution to this problem was based on the fact that there is only one electrical thing directly connected to the throttle - the potentiometer on top of the pump.

I fiddled with this many years ago when trying to get the tickover speed down from permanent fast idle. Had no effect until I understood the purpose of the electrovalves and vacuum system which actually controlled the idle speed. It was only by accident that I discovered that by rotating the potentiomener that the electrovalve activated and the idle speed dropped to normal.

Since that time various vacuum hoses have died and the car runs at fast idle all the time. Will need to sort it some day!

At MOT time last month the car failed on excess emissions. The tester advised running the tank low and putting in a dose of injector cleaner. As the tank was almost full I decided that in order to give it a fighting chance I'd also put injector cleaner directly into the fuel filter. At the same time I also adjusted the potentiometer position. Don't know if this helped, but it went from a figure of 3.02 (Fail) to 0.79 (and a "Fast Pass" at that!).

So when this week I was trying to work out why my aircon wasn't cold I discovered, like you, that the compressor clutch wasn't kicking in at idle and only working when the revs were increased. When it was revved the clutch kicked in and the compressor ran, but only until the revs dropped again and the clutch dropped out. A slow anti-clockwise adjustment of the potentiometer with the engine running and the aircon turned on and all of a sudden the compressor kicked in.

Might be worth looking at it - especially if you have a fast idle issue as well.

They are all connected together.as i said before or should i say inter linked! bit like domino line thing? that bit on pump needs to be set with computer/reader thing. as that does idle.return gas/egr.cold running ie enrichment/fast idle/pump timing.it tells ecu speed of engine so ecu setts/reads everything else.quite often its the electro valve fails then cold starting/fast idles stays on which then up emissions.they can be changed to late ones ie HDi ones don't fit on bar but just zip tie it on. check you have or where vacuum disapears ie pump/pipes/esv? once thats working and the throttle position senser is sett correct you could find that air con will work correctly.plus emissions will be right down.the other one do's egr valve if that don't work it will run like a dog as taking gasses back into engine all the time.you can put injecter cleaner into fuel filter housing(Forte which is good) best time is when hot then take for fast run.
When had sim prob with mine.guy i use has the bosch unit which dealers use the amount of info it gives you is great and you dont realise how much each thing effects each other as you sett it up and read info coming back!. I'd get that sorted out first so engines running correctly then your playing fields abit more level?

[Dommo]

Presumably nigelc doesn't use the forum any more? I hope he does!

I have this problem with my 306, a 1.9 XUD TD, Bosch fuel pump. There are no electical connections to the fuel pump apart from to the stop solonoid, so that rules out the potentiometer you mention Paxman Power.

nigel, did you ever sort it? If so, what did you do?

Thanks.

[Xaccers]

Cassy is doing the same.
Will have to check my other cars to see if they also do it as it could be normal.
What I noticed with Cassy was when the button is pressed on idle, the compressor kicks in for a while then disengages.
After a while, it kicks in again for a short period, then disengages.

My hypothesis is thus:
The air con rad gets very hot, hot enough that when driving on a hot day the temp guage can rise up above the usual 90C
Now imagine that rad getting hot with nothing but the rad fans to pass air over it.
The temperature is going to rise pretty quickly and potentially head for an over heat.
So instead, when you're sat idling, the air con pulses.

That's of course assuming Cassy's working properly and it's not supposed to be running all the time!