After 3 years of ownership the faultless track record was broken in some style today as 31 degree temperatures and queuing traffic on the A27 found a weakness in the cooling system of our 1994 Audi Cabriolet. Well, I think actually the heater matrix - the plumes of steam from the demister vents and the puddle of hot water in the passenger footwell would certainly point to that I think?
I suspect heater matrix repair or replacement is a dash-out job and so this could be the end of the road purely on economic grounds...a shame if so. On the other hand, it cost £536. It's had roughly £500 spend on repairs (replacement rear screen - it's plastic and had gone cloudy, minor paintwork to smarten it up and, ironically, a replacement thermostat). It's had another £800 or so spent on servicing, MOT and consumables. So around £50 a month if it is now scrap. Not bad really I guess!
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>..31 degree temperatures and queuing traffic on the A27 found a weakness in the cooling system
>of our 1994 Audi Cabriolet. Well, I think actually the heater matrix...
You had the heater on today?
Respect!
Seriously though, if it's otherwise good and you enjoy the car I'd get an estimate to fix it.
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Haha no, no heater. But as that's where the steam / water seems to be coming from I'm assuming that it's what faulty...? But it is just an assumption...
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Could it just be a hose or the valve leading to the matrix that's failed?
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Steam, or water vapour?
It's not unusual in these extremes of temperature and humidity to see water vapour out of the vents when the A/C's on!
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It's the puddle of hot water I think he believes points to a problem that may not be economically viable on a 22 year old car.
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Do you use the car in winter?
If not, and you can manage without a heater, can you not just bypass the heater matrix by connecting the inlet and outlet pipes together under the bonnet.
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Certainly an option...need to get it looked at really...
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Does sound like the matrix
My brother had this on his 80 and did exactly what VX suggested above, the pipes are just below the scuttle a quick measurement and off to the plumbers merchant where an appropriately shaped brass connector was purchased for around £1.
He only used the car for to and from work (about 4 miles each way) and the repair outlived his ownership of the car.
As always
Mark
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Well, I did eventually get round to doing something about this today. Somewhat impressively it started first time after being left standing since the date of my last post on this...I make that 11 weeks!!
The heater matrix pipes were indeed easily accessible, and a quick £1.56 plastic washing machine inlet hose joiner and it's fixed. I know, I know it won't be designed for either the temperature or the pressure... but as it works I'll get a bit of copper pipe and upgrDe the temporary fix sometime ;)
i1296.photobucket.com/albums/ag18/C4P_PeterS/Audi%20Cabriolet/IMG_0378_zpsvraedmh5.jpg
All is well, the car goes and doesn't emit steam anymore...however, I'm not convinced that the cooling fan is cutting in anymore. Perhaps I'm paranoid now, but ithe temperature gauge did seem to creep a bit higher than usual but no sign of the fan cutting in... could overheating have caused it to malfunction?
Last edited by: PeterS on Sun 9 Oct 16 at 17:36
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>>
>>
>> All is well, the car goes and doesn't emit steam anymore...however, I'm not convinced that
>> the cooling fan is cutting in anymore. Perhaps I'm paranoid now, but ithe temperature gauge
>> did seem to creep a bit higher than usual but no sign of the fan
>> cutting in... could overheating have caused it to malfunction?
>>
Paranoia perhaps?
After an overheat you are watching the gauge like a hawk whereas previously a glance would satisfy you. Easy to start questioning how high the needle goes.
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I'm no expert but ISTR reading that most cars no longer control the heater temperature via a water valve. Instead the heater matrix is permanently in the cooling circuit and the cabin temperature is regulated by blending ambient/aircon cooled air with that drawn over the matrix according to the cabin temperature set. Excess heat from the matrix is dumped overboard.
If that is the case then removing a 'mini radiator' from the cooling circuit might well affect the temperature gauge. Whether the fan cuts in is another question dependent on the cooling capacity of the main radiator.
Can you leave the engine idling until the fan cuts in - or the temp gauge moves into the red.
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Yes, that was my understanding of how the heater worked, so bypassing the matrix must limit the cooling capacity somewhat? I left it idling for half an hour after taking it for a quick spin; car was definitely up to temperature - a 2.6 V6 doing 24mpg warms up pretty quickly ;). The temperature gauge definitely went higher, but didn't reach the red line and the fan didn't cut in. Will experiment further next weekend!
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Good news! Despite having been unused since it went wrong in the summer, bar the quick drive to test my bodge, it still works. I am pleased to say that today's cold, bright bank holiday shamed / tempted me to do something about its rather down at heel look, with 5 months of accumulated dirt and dust...
Amazingly it started, slightly reluctantly, but you can't begrudge the battery being slightly grumpy having not been used for the best part of three months! So a quick drive to the shell station for £40 of unleaded. 60p of air to inflate all the tyres from the 27psi theyd deflated to back to the 32 they should be. 5 miles to Homebase for £6 of exterior wash and then 30 miles of well wrapped up top down motoring in the sunshine! The rest appears to have fixed the loose connection that made the electric window switches on the drivers door temperamental - back to full functionality. They always worked from the centre console button, so it never bothered me that much. But a new electrical problem has emerged... with the lights on dipped beam the wipers turn themselves onto their intermittent setting. Sidelights = no wipers. Dipped beam = intermittent wipers, regardless of the position of the wiper stalk! Oh well... The lack of heater did make the drive somewhat bracing, despite gloves, scarf, hat, gillet, thin wind-proof jacket and insulated coat though!
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>>But a new electrical problem
Bad earth?
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Not a bad shout...hadn't considered that. Thanks :)
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Retro problem, a bit like carb icing. Look on HJ posts in technical from 15 years ago and it's all about bad earths and carb icing.
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Heater systems with water valves have been long superseded. Think I remember an early Mini with one (circa 65, passed my test in it), but pretty sure everything I've owned has just drawn the air past the heater radiator or not as selected.
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Many cars still have water valve heaters-in fact,some vehicles have been changed from air-blend to water valve because it's much cheaper tho' less responsive than air-blend.The water valve now tends to be controlled electrically rather than mechanically.
Last edited by: jc2 on Mon 10 Oct 16 at 08:14
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Interesting. Which vehicles still have water valve? Presumably you would notice an overall drop in water temeperature when switching on the heater with a water valve system as against an air blend.
The old trick of turning on the heater if the engine was overheating woild presumably not work with an air blend system
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In the early days of heaters,the water valve turned of the water flow completely-now many manufacturers use water heated manifolds to speed-up warmup and allow weaker mixtures during the warm-up to meet more severe emission regulations and therefore the water valve does not shut off the flow but by-passes it back to the engine so that the flow is maintained.
The old trick would still work on air-blend systems if you put the fan to maximum speed and open a window.I used to have to turn off my air-conditioning on a car with air blend because it was putting more heat into the radiator but that has nothing to do with the system fitted-just an elderly cooling system-not required on my current car.
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"The old trick would still work on air-blend systems if you put the fan to maximum speed and open a window."
I'm not sure I understand that. If the engine heated coolant is constantly flowing through the heater matrix whether the heat is used in the interior of the car or efectivley dumped to the outside world the cooling effect on the engine is is the same isn't it?
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Putting the fan on max-flow and the heater on max-heat,gets rid of more heat and eases the load on the rest of the cooling system.Very early Renault 16's used the heater matrix as the main radiator but soon changed to a conventional cooling system to make use of the natural airflow from the movement of the car.
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OK, I understand now. Thanks
As an aside when my son was small we use to have a Lada. The car might have been rubbish but the heater was huge being designed to cope with Moscow winters. We used to put it on to max and see how long we could stand the tropical heat!
Last edited by: CGNorwich on Mon 10 Oct 16 at 11:43
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Cars built for European territories have different build specs for particular markets.Northern countries take bigger heaters and smaller radiators-Southern Europe gets the opposite.
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That's interesting jc2. We have this fantasy, pipe dream, half baked plan, call it what you will, of one day, when or if life circumstances allow, of just heading the car across the world or even round it for a couple of years.
Wonder if it'd need to have any cooling adaptations.
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Should still be adequate-just not so much in hand as it gets older and furred up!
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>>have different build specs for particular markets
Absolutely.
At one point a bunch of European Astraswere sold in Brazil as opposed to the more usual Mexican built ones. The aircon died on them all.
It is also surprising how often a part for one of my cars, even if it exists in Europe, is different.
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The average British car does not have aircon that will cope (properly) with the south of Spain in August.
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Air conditioning can be a blessing if the car has been standing in the sun for hours, but never for very long. I always open the window or windows and just tolerate the weather. Moving air however hot is cooling because it helps evaporate one's sweat (often copious in my case).
Moreover a/c is wasteful of fuel and reduces performance noticeably. One is supposed to run it on full blast for an hour or so every week or month, but I usually forget.
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25 years ago SWMBO won a 2 week holiday for 4 in Estepona - flew into Gibraltar.
That's the good news - the downside it coincided with Border issues & slow clearance @ the Border.
Hire car was a Subaru Legacy saloon WITH AC!!!
We sat the 2.5 hrs with the engib=ne on, keeping our cool whilst 90+% of people around us were fanning themselves & failing to make much difference in the July heat.
Odd config for the car by UK standards - only had a AM Radio & very few toys.
Did the job, never missed a beat in our free 2 weeks - car was my expense but hey! a free holiday.
Never won anything since other than a few pounds on the lottery.
.
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>> Moreover a/c is wasteful of fuel and reduces performance noticeably. One is supposed to run
>> it on full blast for an hour or so every week or month, but I
>> usually forget.
The a/c in the Lexus runs the compressor from the battery so no impact on performance. Don't really think it makes any difference to economy either
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>> The a/c in the Lexus runs the compressor from the battery so no impact on
>> performance. Don't really think it makes any difference to economy either
The car might be smart enough to reduce generator load when maximum power is demanded, but I can't see why it would take materially less energy to drive the aircon just because it is converted to electricity first. A bit less friction I suppose if it removes a pulley, which would offset the generating and charging losses.
I will say though that the effect of aircon on economy seems greatly exaggerated. I've never noticed it. I expect it's much higher when it's very hot and it has to work hard, but I'd use it then anyway.
Mine is on all the time. Never steams up, apart from anything else.
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>> The a/c in the Lexus runs the compressor from the battery so no impact on
>> performance.
Did you say what model Lexus? The fact some are now available as hybrids suggests using the battery makes sense. If the engine is not running then you'd get no AC.
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>> Did you say what model Lexus? The fact some are now available as hybrids suggests
>> using the battery makes sense. If the engine is not running then you'd get no
>> AC.
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Its a CT, so yes, its a hybrid.
The a/c, (and I think pretty much everything else), is powered by the traction battery- the 12V does little more than power the electronics to start the system.
The fact the a/c runs without the engine running is a nice bonus in traffic on a hot day - not something that happens with a normal stop start system
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>>not something that happens with a normal stop start system
It does if the engine is still running ;-)
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>>The a/c in the Lexus runs the compressor from the battery so no impact on performance.
>>Don't really think it makes any difference to economy either
Mikey, perhaps you'd let us all know where the free energy comes from as we'd also like some.
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>> Mikey, perhaps you'd let us all know where the free energy comes from as we'd
>> also like some.
Not sure I said any energy was free, but as the traction battery is charged through regen whenever I coast or touch the brake pedal.........
Last edited by: VxFan on Fri 21 Oct 16 at 16:43
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Audi 80 Cabrio - 22 year old Audi finally blots it's copy book... - Kevin
