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Where is the internal sensor Pages: 12Last

jezzer on Mon August 03, 2009 3:43 PM User is offline

Year: 06
Make: MG
Model: ZS
Country of Origin: United Kingdom

Hi Again

Im still trying to find out why my aircon doesn't really cool the car,Ive been told it could well be the internal sensor and by getting to that the dash has to come out.

Could someone give me as much info on this sensor as they can,Im having big problems with vospers and will be talking to the manager in the morning,So it would be good if i can talk to him without looking like i dont know anything.

I take my my car into vospers to have the sensor looked at,4hours later they have said its all working,When i got to vospers all i found out they did was pressure checks and to check how cold it was.

It didn't go in for that it went in so the dash could be pulled out,Not Happy

Thanks

Edited: Mon August 03, 2009 at 3:43 PM by jezzer

Prospeeder on Mon August 03, 2009 7:46 PM User is offlineView users profile

Well it detects how cold the evaporator is, so it can cycle the clutch to maintain a certain temp. if the sensors bad, then it will trick the system into thinking its too cold and not work.

-------------------------
1990 Pontiac Turbo Grand Prix
1990 Pontiac 6000 LE V6
Both have R12 A/C

jezzer on Tue August 04, 2009 4:00 AM User is offline

Thanks,I just dont belive vosers ive talked to the manager and he is telling me if its coming out cold then its working ok,He doesnt understand what i mean the car doesn't cool off.

Edited: Tue August 04, 2009 at 4:07 AM by jezzer

mk378 on Tue August 04, 2009 10:34 AM User is offline

Maybe your pollen filter (if equipped) is clogged, or the interior fan is not working at full speed, or mice have moved into the ductwork. These problems will have cold air leaving the vents, but not in sufficient volume to keep the car cool.

jezzer on Tue August 04, 2009 11:58 AM User is offline

Hi

Thanks for your suggestions

No its not anything simple thing like pollen filter/fan motor ,Ive been told by one mechanic to look at the sensor because he has a strong feeling thats the cause,But can i get vospers to look at it nope,So far the manager is saying it cant be anything to do with any sensor if im getting the right temp out of the vents.

EDIT:

So do you think if the internal sensor is a bit faulty then this could be why the airvents is blowing nice and cold but the car isn't cooling down?

If the manager does phone me again i want to be ready for him when he might say there is no way the sensor has anything to do with the car not cooling down.



Edited: Tue August 04, 2009 at 1:13 PM by jezzer

bohica2xo on Wed August 05, 2009 2:12 AM User is offline

It is hard to say, without really knowing what that car actually is.

MG ceased to be MG decades ago. It was BMW junk for a while, then "Rover". My last recollection of the Rover 45 (which was rebadged as an MG ZS) was that it was basically a Honda Civic platform... that was in 2005.

So what exactly is an '06 "MG ZS"? And how much of it's subsystems are similar to the US models we work on? For instance the Vauxhall Astra is sold here as a Saturn, and I would have to look it up as such.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Wed August 05, 2009 9:28 AM User is offline

Tis easier to pop open the bonnet to learn very quickly what you have, in a CCOT system, uses an accumulator mounted between the outlet of the evaporator, the large tube to the inlet of the compressor. In a TXV system, uses a receiver mounted at the outlet of of the condenser to feed the evaporator with the small tube. CCOT uses a fixed orifice where when the evaporator gets cold enough, low side pressure drops, and cuts off the cycling switch, the compressor stops. A TXV system uses a variable orifice that closes when the evaporator gets cold, but it holds the low side pressure up, so it is possible that the evaporator will get so cold, it will ice up blocking all air flow. TXV systems are better than CCOT systems as the cycling of the compressor is greatly reduced. Compressor is forced to rev up from zero to the engine speed in no time flat, that causes severe stress and wear.

But since the evaporator can ice up, a thermal switch has to be added to switch off the compressor, it cuts off the compressor if the evaporator drops below 1*C and switches it back on at around 4*C. A failed thermal switch would either let your compressor run all the time or not at all. So is your compressor running?

I have no problem in my 4 banger Cavalier knowing if the compressor is running or not, can both feel and hear it, neither with the motorhome with that large York sitting next to me, but do have problems in my Cadillac with a large V-8 and lots of padding. Point is, can you hear your compressor running and is it running? If it is warm outside, AC is on, it should be running, if not, would suspect problems in that thermal switch or any of the components, like a relay not switching on the compressor. A non-running compressor causes warm vent air.

But on the other hand, if the compressor is running and getting warm air, you have different problems, here pressure readings are very important. TXV's do fail, can be a leak, the dual function switch, either over or undercharged. Sounds like what you need is a guy that not only understands AC principles, but can learn very quickly what the problems are. This can be all done much faster than it took me to type this. Know what kind of system you have, listen to it, take pressure readings, and observe if the compressor is running or not. Also a hand feel of the system tells a lot, can either be mechanical or electrical problems, have to keep an open mind. Idiots cannot do this.

jezzer on Wed August 05, 2009 9:54 AM User is offline

Hi thanks for your info

I know the compressor is running when im starting off but i would never able hear it while im driving as its a noisy car,I would be happy to let the local guy who owns a garage do the work for me,I have a feeling i might have to let him,But im trying to push vospers to look at it as its allways been like that when the car was bought new under warranty.

You say a failed sensor would run all the time or not at all,But what about if it wasn't reading it right and switching it off then on,Say every 5minutes would that be plausible?

Ive just got a bad feeling about vospers im sure they dont know enough about aircons.

I phoned up the complaints this morning because the manager never phoned me this morning like he said he would, they said they will get in contact with the manager,So far ive not heared of anything.

My local guy was sure it was something under the dash i wish i took it in when he first said there was a problem with my air-con,All i remember him saying is he would need to take the dashboard out.

Thanks Again

Edited: Wed August 05, 2009 at 10:12 AM by jezzer

NickD on Wed August 05, 2009 11:26 AM User is offline

I was never happy with the MVAC system in my old 86 Civic hatchback, in sub zero, would take ten miles of driving to get any heat, and in summer, only a barely cool breeze from the AC. But what the heck, could carry all my equipment, got great fuel economy, and used it mostly to haul my pups and do airport work. Pups didn't complain about the environment, and my airport work was outdoors, the interior of the car was better than that. But the system was optimized, point is, you can have a vehicle that no mater what you do outside of a major redesign, it doesn't work worth a crap. Do you have such a vehicle?

bohica2xo on Wed August 05, 2009 11:37 AM User is offline

Sure glad I don't live in the UK. It appears the only choices are a dealer that will not even return a phone call, or an independant that "guesses" at a dash removal - a pocketbook raid is more like it.

Your issue could be anything - low charge / clutch air gap / electrical fault / failed switch / out of calibration sensor / damaged / clogged / moon phase...

Without knowing the type of system everything is a guess. Some systems have TXV's. Some vehicles have variable displacment compressors. Some use evaporator pressures to sense & prevent icing, others use thermistors in the air stream. Some cars evaporators can be serviced from under the hood, some from under the dash, and some need a pillar to pillar dash removal.

You may have 3 sensors under that dash - or none.

To be fair, the UK is not the only place with "pocketbook raiders". One shop here in town tells anybody with a dodge / chrysler FWD that they have an evaporator leak. But with 15+ shops to choose from, they only bag so many...

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jezzer on Wed August 05, 2009 11:48 AM User is offline

Quote
Originally posted by: bohica2xo
Sure glad I don't live in the UK. It appears the only choices are a dealer that will not even return a phone call, or an independant that "guesses" at a dash removal - a pocketbook raid is more like it.


B.

I think you may of not read it right,I was the one who didn't take it in when he was talking about the dash,And when i popped over to him the other day he said it should be the sensor under the dash thats the problem,Now he said should be because he wasn't talking to me face to face,He was under someone elses car so he didn't really have the time to talk me through it and why should he if he is not doing the work,Well put it this was i trust him with my car more than vospers he knows about the MG cars as he worked for them for 10+years

Ive been told the ZS aircon is good,No doubt he would find the problem alot faster than vospers.

NickD on Wed August 05, 2009 1:14 PM User is offline

Vospers is a foreign word to me. I just like to handle the mechanics of an AC system first, do this by having manual control over the magnetic clutch, test the current, pull in, current when hot using a variable power supply directly to the clutch coil. Can test for pressures, vent temperatures, line temperatures, fan, TXV, condenser, evaporator, and compressor performance. But have to be awake as all safety devices are bypassed. With that under my belt, it's all electrical.

Electrical can be as simple as the mode switch on the climate control panel feeding 12 V to a cycling switch to directly activate the clutch coil. Or as complicated as a microcontroller with data links from the BCM and the PCM with sensors located all over the place. Sure helps to have a circuit diagram of what you have.

bohica2xo on Wed August 05, 2009 1:43 PM User is offline

Huh. You trust this mechanic so much you are posting on a forum looking for answers...

But will not divulge one detail about a car that is not imported here to several people willing to help you.

Your problem could be a blend door issue, an actuator, cable adjustment, etc.

How about this. Just tell us the actual vent temperature of the discharge air, and the ambient air temperature at the time of that measurement. All it takes is a thermometer shoved about 2 inches (50mm) into the dash vent.

Otherwise we can guess all week with no result.

B.


-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jezzer on Wed August 05, 2009 2:14 PM User is offline

bohica2xo you have really not took on board why i made this thread,I trust the garage near me because i will know if he does my aircon he will find out what the problem is,But that would mean paying i do not want to pay because its a fault that vospers should of done while it was under warranty,So this is why vospers had my car at no charge,But they didn't do what was asked.

So i asked on here where is the internal sensor,So i could tell vospers this is what im talking about.

Im not looking for any other answers that was all i was asking because vospers will have to look into this.

Intake Temp 20-24c Outlet Temp4-14c,Thats all i know because i have no thermometer,This is what vospers printed off.

Thank You

Edited: Wed August 05, 2009 at 2:16 PM by jezzer

Karl Hofmann on Wed August 05, 2009 6:54 PM User is offlineView users profile

The ZS is indeed based on the Rover 45 which was a rehash of the Rover 400 which was based on the Honda Civic... The ZS was one of the last products of the now obsolete Rover group.... Needless to say when Rover went belly up and was sold off to the Chinese, the dealer network colapsed and all warrenties were null and void, so for a dealer to want to involve itself where the warrenty has long expired on a car that is now history would be seen as foolhardy...

Every garage and his cat are now Air conditioning experts here now since the massive push from the equipment suppliers to sell refrigerant management stations to cash in on the air conditioning service boom... It is now rare that I get involved in car aircon since the customer measures good service by low price. If I do work on a car, then it is usually what others can't fix.

The ZS utilises the Sanden SD7V16 compressor and so does not have an evaporator sensor.... Please refresh my memory, did this car have an issue with the selection of vents? would only blow out of certain vents?

-------------------------
Never knock on deaths door... Ring the doorbell and run away, death really hates that!

jezzer on Thu August 06, 2009 4:54 AM User is offline

Hiya

I did say there was a problem with the vents it could of been the blend door not closing as it should,But vospers are saying thats not possible,Vospers said you would able to feel the air escape if it wasn't shutting as it should.

NickD on Thu August 06, 2009 6:53 AM User is offline

Just drive the car with the AC off, if the vent air is warmer than sticking your hand out the window, you have blend door problems. It will be warmer if the car sat out in the sun for awhile, you get more accurate results if you do this test at night. Does your car have head lamps?

Karl Hofmann on Thu August 06, 2009 9:25 AM User is offlineView users profile

Quote
Originally posted by: jezzer
Hiya



I did say there was a problem with the vents it could of been the blend door not closing as it should,But vospers are saying thats not possible,Vospers said you would able to feel the air escape if it wasn't shutting as it should.


If the full flow of air isn't blowing from the vents that you select, then that is your problem... I had a ZS that suffered from this problem a whiles ago... Would only blow through demisters and on to feet. I gave the customer a price to pull the heater box as all of the cables and controls were working correctly.. but it was probably more than the car was worth...

Nick, the ZS uses high intensity tallow candles.




-------------------------
Never knock on deaths door... Ring the doorbell and run away, death really hates that!

NickD on Thu August 06, 2009 9:58 AM User is offline

What are demisters? Defrosters by any chance? Is this a vacuum or a cable system? There are also servo motorized systems, those get hairy. Was complaining about that heater control valve when I first got my motorhome, bohica2xo responded, but ended up pulling the dash anyway as found many other problems. Cable was long enough so I could cut a couple of inches off of it, but youse guys, that's about 5 cm. Pulled it out, sanded the rust off of it, and applied a thick coating of silicone grease, bend in a new hook, been working fine since then. But to say it's impossible for a cable to freeze up is ludicrous. 90 T-Bird also has cable blend door problems, just have to crawl under there and fix it. Don't even need electronic test equipment, can see what's going on. Just a question of doing it, or paying someone to do it for you, or living with it.

I was all set to buy a new MG, that coupe, can't even recall the name of it back in 1978, got the cash, went down to the dealer, but the price went up around a thousand bucks with some kind of new tariff, so never did buy the darn thing. Why aren't we charging those high tariffs with the Asians? UK and the USA use to be friends, now we are screwing each other, not we, but our governments.

In the 50's and 60's, the UK was my first choice in purchasing some of the finest electronic components in the world, still have my Garrard turntable, but that is ancient history. Sounds like youse guys are making the same kind of crap, we are. And this thing is only three years old?

bohica2xo on Thu August 06, 2009 7:19 PM User is offline

Quote
Originally posted by: Karl Hofmann
The ZS is indeed based on the Rover 45 which was a rehash of the Rover 400 which was based on the Honda Civic... The ZS was one of the last products of the now obsolete Rover group.... Needless to say when Rover went belly up and was sold off to the Chinese, the dealer network colapsed and all warrenties were null and void, so for a dealer to want to involve itself where the warrenty has long expired on a car that is now history would be seen as foolhardy...



Every garage and his cat are now Air conditioning experts here now since the massive push from the equipment suppliers to sell refrigerant management stations to cash in on the air conditioning service boom... It is now rare that I get involved in car aircon since the customer measures good service by low price. If I do work on a car, then it is usually what others can't fix.



The ZS utilises the Sanden SD7V16 compressor and so does not have an evaporator sensor.... Please refresh my memory, did this car have an issue with the selection of vents? would only blow out of certain vents?

But, But, But, it is the under-dash sensor! LOL. Thanks for clearing that one up Karl. Now I DO know what the control system is, as well as the platform.

I guess a thermometer is a a big cash outlay anymore. How can one complain about the vent temperature without a way to measure it? I am seeing 4.5c vents with a 46c ambient on an untouched 2 year old system with 30k miles - so I will go out on a limb here and say your system is not doing too well...

B.



-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jezzer on Fri August 07, 2009 12:06 PM User is offline

Sorry ive not had time to reply

Ive eventually had a meeting with the manager and they have agreed to look at the internal sensor,The mechanic looked underneath the glovebox area and said the blend door was ok.

But they are both saying there is nothing wrong with the coldness of the airvents,But once again im trying to tell them the coldness out of the vents is fine.

Edited: Fri August 07, 2009 at 12:12 PM by jezzer

Karl Hofmann on Fri August 07, 2009 3:39 PM User is offlineView users profile

Ok Jezzer... Lets take this back to basics..... When you set the vents to blow out of the face vents, does it blow out of the face vents? what temperature is the air coming from the vents and how far do you drive or how long do you run the engine before you measure the temperature a the vents, and also what temperature is the cabin...

Traditionally I have found the aircon on the rover 400 to be pretty good, quite possibly the best bit of the car but the ZS was hacked and butchered by engineers who had no money and knew that they would soon be out of a job. It is possible that the airbox had been cheapened or made by another company to a lower standard. I really do believe that this is an air distribution issue.... Provid enough air at the right place and the car will be nice and cool.

Jezzer, Is the car under some kind of warranty?



-------------------------
Never knock on deaths door... Ring the doorbell and run away, death really hates that!

jezzer on Fri August 07, 2009 5:34 PM User is offline

Hi

No its not under warranty which is a shame,But when it was under warranty i was allways saying its not cooling the car down but they allways said yes its fine,So they have said out of good will they will check the sensor and airducts.

Vent temp is 46-7f,Thats in the centre vent ive tested the vent temps different ways doors open etc,Ive kept it in the vent for a two hour drive but its allways the same temp,Yes the face level vents work vospers have told me all the vents are getting the right amount of flow from each vent.,The cabin temp was 60f when i got in the car i did open the windows for about 10minutes before putting the air-con on.

What you say about putting cheap stuff in the car i can see why you say that so that could be part of the problem.

Is there a better way to test the temp?

Cheers

NickD on Fri August 07, 2009 6:01 PM User is offline

Exactly what is the problem, I mean not thinking it could by the internal sensor, strictly in terms of operation and performance. If you can bake bread in the car with the AC on, that could be a problem.

jezzer on Fri August 07, 2009 6:21 PM User is offline

The problem is the car doesn't cool down on a hot day no matter how long im driving,The car stays very warm at first i thought it was just me,But when it went for its first M.O.T i asked about how good the aircon is and it started from there my local garage confirmed what i thought,He said its just not cooling down its pumping out the cold air but thats it.

EDIT: I forgot to say i had a new motor put in for the blower because it was slowing down.

Edited: Sat August 08, 2009 at 2:53 AM by jezzer

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