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MG ZR ZS ZT Technical - ZT Air con noises

Anybody else had any problems with their ZT aircon system? Mine has started making "mooing" noises, I suspect it is from the servo motors that control the valves etc tucked away in behind the centre consul somewhere. Maybe the control rods need some lubrication so it's just a matter of finding them - looks like a heater out job so just wondered if anybody has got an easy answer!!! 97,000 miles without a problem which is a good record but my drivers central locking motor has just failed (got another one using 24/7 spares web site - excellent source of parts at half the usual cost) and now the air con is making worrying noises. It is worse at idle when it tries to cool and then when you switch the engine off this groaning mooing noise comes out of the bulkhead! No I haven't been drinking!

Geoff
G Calvert

You haven't got a cow's backside sticking out of the front, have you?
Paul Hunt 2

Hi Geoff - mine has been mooing ever since I bought it - doesn't seem to affect the performance, and I beleive it has something to do with the clutch system on start up. Seems to do it more if I start up quickly, ie put it into gear as soon as the engine catches, rather than wait a few seconds.

Cheers...
Malcolm Robertson

Sorry for the late reply but do not often look here.

Our 75 Estate (2.5 V6 auto) starting making this mooing noise on start up and thought it rather funny. However driving along one day in slow traffic the temperature gauge shot up and we got that sickly sweet smell of boiling anti freeze. Diagnosis was a failure of the fan assembly. Car taken to friendly Rover dealer and complete twin fan unit was replaced.

No more overheating, not more mooing and no more £500!

I understand these units are in short supply but also believe it is possible to replace the fan(s) motor and that Kenlowe are now making replacement parts. I have not look into this too much as I assume I will not have the problem for another 6 years! Bloody BMW parts!
Patrick

Thanks for the info - I don't think it's the fan as the noise stops as soon as I turn off the aircon but I will certainly check.
G Calvert

It is the fan. The fan is supposed to run at low speed when the air con is on so air passes through the condensor.

You will find that your fan doesn't work on low speed any more.

If your car is an 04 or newer you are lucky because it can be fixed by replacing a resistor that has burnt out. This will cost in the region of £25 for the part.

If your car is earlier than an 04 it is highly likely you have a three speed motor and the brushes for the slow speed have burnt out. New motors are in very short supply and are currently changing hands for £400-500. I was lucky and managed to get one for £180 six months ago but stocks have dried up since then

There is lots of information about this very common fault here

http://www.the75andztclub.co.uk/forum/showthread.php?t=1371

More info on the replacement resistors and the Kenlowe alternative can be found on the same site

Andy
Andy

Andy - if the fan isn't working on low speed, what is making the mooing noise? My fan seems to work, but I confess it is hard to determine which speed it is running on, and the mooing is quite intermittent. I bought a new three speed fan last year but I haven't yet fitted it. I plan to do so in the next few weeks before the antipodean summer hits in full force. Should the mooing stop once this repair has been done?

Malcolm
Malcolm Robertson

Malcolm,

There are a lot of different combinations of fans and wiring depending on model and year of car but if the engine is running and a/c is selected then I believe in every case the fan is supposed to operate on its lowest speed. If it doesn't then there is no cooling air passing through the condenser. The condensor sits in front of the radiator.

Because there is no condensing happening eventually the system pressurises until a relief valve actuates and the mooing will start. After a while say 10 minutes you will notice the aircon doesn't blow cold anymore. When on the move there is sufficient air flow for the a/c to work without any help from the fan.

Replacing the fan solved my noise. The website I referenced earlier contains how to on dismantling the front end. I'd say allow 3 - 4 hours although others have done it in less.

If you replace like for like there are no problems but if you replace an early three speed motor with a later two speed one you have to replace the control box too.

If you run with aircon on all the time the three speed fans don't usually make it past 45,000 miles. The two speed fans have doubled up the brushes to make them last longer and achieve their dual speed by switching a resistor in and out of the supply circuit. Sadly, the resistor can't cope with the current it is expected to handle and burns out usually in the first 30,000 miles. Fitting a replacement is cheap enough but involves pulling the bumper off

Hope this helps

Andy
Andy

You are right my fan has stopped and at last I understand the mooing!!! So I hadn't driven up a Cows backside after all!!

Thanks for the info - got to find a fan now!!

Geoff
G Calvert

Thanks Andy - watch for an "our MGs" report in MG Enthusiast on this in the future when I do the fan job! I'm sure something will go wrong...
Malcolm Robertson

Fan job completed and thanks to Andy for his advice and link to the 75 and ZT forum which has a great set of instructions. Initially I had problems sourcing a fan, my main ex MG dealer told me no chance of a new one as they had all gone to China and Rover Breakers told me they were very rare but they had one for £210, which for a 2nd hand part I thought was excessive!! Anyway after a search on the UK scrap yard websites I ended up with two offers at a very reasonable £40! So all fitted and working well (2 weeks since fitted) although it didn't work initially, seemingly waiting for the ECU to sort itself out and activate it after about 15 mins running when the outside temp sensor returned to normal (see 75 and ZT forum link). When I get time I will try and take the old motor to pieces and see if I can find some way of replacing the brushes ready for the next time! Sounds like I was lucky to get 97,000 miles out of the first one!

I have also changed the drivers locking motor £35 again from internet breakers searches - if anybody else needs to do this DO take the glass out - I didn't as I was worried about getting it back and fiddled for ages as the link to the outside door handle fell off - in the end took the plunge, removed the glass and finished the whole job in half an hour - it's not that difficult!!

The other problem, they all occured at the same time, was a cracked flexible joint on the exhaust. I was quoted £850+ for a new exhaust from the dealer as they are a one piece design including the cat and £375 from an exhaust centre who had a front section with cat. Ended up getting a friend to weld on a flexible joint he found in his skip which was in good condition for £40 - bargin! looking forward to another 97,000 now!!

Thanks again for the info

Geoff
G Calvert

Glad you managed to fix it Geoff. I got my fan from Rover Breakers. He is selling new ones, at least he was when I got mine. It was boxed up with controls and shroud.

As well as breaking cars he seems to have a lot of pallets and crates that have obviously come from Longbridge or Longbridge suppliers.

A lot of people are trying to source brushes. It's not just about size! The copper content has to be high enough to handle the current.

I've got a clutch that is just starting to slip at 65,000. That seems to be low mileage so maybe there is fluid contamination on the drive plate.

Anyway I haven't got the equipment or garage space to do that myself so i need to shop around for a quote.

Andy
Andy

That might explain the high price but he didn't say it was new! Hope you get the clutch fixed I have a friend who used to be a Rover dealer service manager and now has his own business but not much good to you up in Manchester!

Good luck.

Geoff
G Calvert

This thread was discussed between 16/10/2007 and 23/11/2007

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