Aircon / cooling fan fault

[ben19td]

Hi all, have searched through previous threads and can't find a definitive answer for my car's particular problems, am hoping someone might be able to help.

I've owned my 1998 406 1.9td since November, so haven't needed the aircon until now. It is very weak so I took it for a re-gas. The garage removed as much gas as they put in, approx 630g and no reported leaks. Aircon still not blowing cold air, but no problem blasting hot air out.

When the car is running and switch the AC on, the revs do not change, I hear no clicking, but the radiator fans come on.

Interestingly this is the only time the radiator fans ever come on, I left the car idling for 20 minutes this eve, temp gauge showed well over 90, but the radiator fans did not kick in at all unless I switched on the AC.

Before I start changing bits and spending loads of money can anyone suggest a probable solution or at least which components to try first? I have a donor 406 that I am stripping the leather interior from, it is a D8 same as mine but a 2.0 hdi whereas mine is a 1.9td

Thanks in advance for any help, and if anyone needs any bits from the donor car just let me know.

Cheers

[Doggy]

I would test the a/c compressor clutch, by connecting it temporarily to the battery via a 10 or 15A fuse and making sure it clicks / pulls in.
(you can identify the +ve pin as it will have a few ohms resitance to the case, the -ve will be a dead short).

If it doesn't, the problem's the clutch, if it does next stop is probably the relay, but I have no idea how a D8 is wired up, sorry.

[ben19td]

Thanks Doggy, will give that a go, weirdly, driving into work this morning I had ice-cold air con, but sadly, not on the way back.

[steve_earwig]

The fans on D8s are handled by the pressostat, it takes info from the temperature sensor on the engine as well as the air con ecu to know when to run.

When the car is running and switch the AC on, the revs do not change

Try holding the revs above idle and switching it on. The idle speed is set by the ecu, you might hear a slight drop but it'll be very quick. Holding it above idle gives you a much better chance of hearing it. I guess it would be good to know if the a/c is actually working but feebly or not working at all because it's sensing a fault or whatever and not even trying.

Try pulling the connector off of the brown temperature sensor on the thermostat housing the fans should run full speed. Check they're both spinning. Btw the relays on these can suffer from corrosion, they're meant to have 2 speeds but they can end up with just one that pulses off and on as the pressostat tries to cope.

[ben19td]

Hi Steve, thanks for your advice, it is much appreciated. I have done as you suggested, I held the revs at around 2000 rpm and there was a very slight change in revs when switching the AC on and off, but still no clicking sound.

I removed the brown plug from the thermostat and both fans came on full speed, much faster than when they come on for the AC.

What does this tell me and what should I try next do you think?

Thanks again for your help,

Ben

[ben19td]

Can anyone follow on from the advice given by Steve please? I am a bit out of my depth with AC and cooling, I'm trying to suss out which model of compressor mine is, so I can keep a look out for a replacement on ebay, but it is so well buried that I can't see a part no. on it.

That said, on the basis that the AC does function and blow cold air approx 50% of the time, is the compressor definately the culprit?

Any help would be greatly appreciated to save me throwing good money away by giving up and taking it to the dealership.

[steve_earwig]

Oops, I missed Sunday's update, sorry (not going senile yet, migraines will do that to you). Umm, if the revs are dropping then it must be some extra load coming on, i.e. the compressor. You won't necessarily hear a click, my 2.1 was usually silent but when I started hearing it click I thought there must be some fault showing up. The fans coming on full is a good sign, I reckon with it doing the low speed too then the relays are ok. Maybe the sensor? I'm not really confident with this as the air con seems to be playing up too and I'm not sure if this would affect it or not, but...

[steve_earwig]

By the way viewtopic.php?f=3&t=15634&p=151849#p151849 (not that I think it's the problem)

[ben19td]

Cheers Steve! So based on all the above, I am going to replace both sensors on the thermostat housing, which I should be able to do without losing too much coolant hopefully. I bought a new thermostat kit the other day, but that will involve major coolant loss so will wait for cam belt replacement to change it.

There is a sensor on the side of the condensor drier, looks like that can be changed without losing any gas, so might be worth a try too?

I will also hunt out the ac controller module, which looks to be housed somewhere behind the condensor drier, near the fan relays, if it's easy to get at I will change that too.

If it's still playing up then maybe I'll have to try a new compressor.

While I'm replacing sensors, I will do the crank sensor as the car runs very rough when first started from cold, and a speedo sensor as I sometimes lose the speedo needle when driving.

Lots of sensors to sort out, but if it works then it's worth it I suppose!!

[Doggy]

There is a sensor on the side of the condensor drier, looks like that can be changed without losing any gas, so might be worth a try too?

Can't promise yours is the same but my last 52-plate 2.2 HDi had a non-return valve under the sensor, (which is a dual pressure switch on early cars and an analogue pressure sensor on later versions).

I will also hunt out the ac controller module, which looks to be housed somewhere behind the condensor drier, near the fan relays, if it's easy to get at I will change that too.

If it's still playing up then maybe I'll have to try a new compressor.

Did you try testing the clutch?

While I'm replacing sensors, I will do the crank sensor as the car runs very rough when first started from cold, and a speedo sensor as I sometimes lose the speedo needle when driving.

Rough initial idling is common on 1.9,s (particulary the vegetarian strain).

Intermittent speedo is uaually a module behind the glovebox, rather than the crank sensor, (if it has one).

[ben19td]

Cheers doggy and Steve, if the compressor was easier to get to I would definately test the clutch, am trying the easy stuff first!

Plus if it works some days and not others, that should mean the clutch is working shouldn't it? unless they can be intermittent?

Will try the sensors on the thermo housing first and see what happens, if no joy will get my mate to do the cam belt and investigate compressor at same time, he is ex pug main dealer, just gone independent, top chap, if anyone needs any work done in wokingham / reading area just ask and I will give out his details.

The joys of old cars, I miss the days of being a pug salesman and getting a brand new car every few weeks! Still, now I sell motorbikes so I've got some nice new Yamaha's to play with, so it's not all bad!

[gumby6371]

If I remember correctly the AC clutch is visible if you pop the wheels up on ramps, then it's just a case of seeing if it spins when you push the button (I think)

[ben19td]

Thanks gumby, will give that a try, whereabouts on the compressor is the clutch, is it within the belt pulley?

[ben19td]

It's ok, I see where the clutch is now, will check it tomorrow.

[ben19td]

So, I did as suggested and can confirm that the clutch spins when the ac button is lit and doesn't spin when the ac is off. So I'm pleased the compressor seems to be ok, but what else could be causing intermittent problems, I have one theory, on Saturday I started the car with the already switched on, and within a few minutes I had ice cold air. Coming home again, I started the car with the ac off, and tried to switch it on mid-journey, but no cold air. Could this be a clue?