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Old 21st April 2017, 08:23   #11
QuestionMark
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Originally Posted by T-Cut View Post
I'd have expected the interior blower to start immediately the aircon system is started. Logically the motor is OK, so I'd suggest looking at or swapping the speed control/transistor pack. This is just a plug'n'play module that you can buy from eBay.

TC
Thanks for the suggestion, I'll look into that! Is it this thing? Rimmerbros item #9, part #ZUA000590

Is there a way to check if the transistor pack works?
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Old 21st April 2017, 08:40   #12
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Sometimes I can drive for a couple of miles with an already warm engine on a hot summer's day before the blower starts up ...
That's definitely not how it should be.

Note however that in cold ambient temperatures when you have selected heating, the blower (or ventilation fan) will notoperate until the coolant reaches a certain temperature. Is this what you're experiencing?
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Originally Posted by Avulon View Post
... try taking manual control of the fan speed and see if the lowest speeds are pushing any air through.
Good suggestion John.

Simon
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Old 21st April 2017, 08:49   #13
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Thanks for the suggestion, I'll look into that! Is it this thing? Rimmerbros item #9, part #ZUA000590
Yes that's correct.

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Is there a way to check if the transistor pack works?
For most of us, swapping with a known good part is usually the way. Cheap enough second hand.

eBay: http://www.ebay.co.uk/itm/Rover-75-M...QAAOxycmBSzDeb

TC
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Old 21st April 2017, 08:55   #14
QuestionMark
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Note however that in cold ambient temperatures when you have selected heating, the blower (or ventilation fan) will notoperate until the coolant reaches a certain temperature. Is this what you're experiencing?
Perhaps I'm being dumb, but aren't heating and cooling the same, just relative to the ambient temperature? Because there isn't any heating or cooling button to select, only the temperature scale. So in 10 degrees ambient temperature every setting will effectively be heating, whereas in 30 degrees every setting will be cooling?

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Originally Posted by T-Cut View Post
For most of us, swapping with a known good part is usually the way. Cheap enough second hand.

eBay: http://www.ebay.co.uk/itm/Rover-75-M...QAAOxycmBSzDeb

TC
Cheers

Last edited by QuestionMark; 21st April 2017 at 08:58.. Reason: Quick thank you to T-Cut
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Old 21st April 2017, 14:12   #15
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Perhaps I'm being dumb, but aren't heating and cooling the same, just relative to the ambient temperature? Because there isn't any heating or cooling button to select, only the temperature scale.
It's more complicated than that, and no-one has succeeded in trying to work out exactly how the decisions are made in 'Auto' mode. If I were you I would carry out the checks suggested to see if you can find a fault with your blower (ventilation fan) control.
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So in 10 degrees ambient temperature every setting will effectively be heating, whereas in 30 degrees every setting will be cooling?
Not necessarily. It also depends upon the interior temperature of the car and there are also sensors on the heater matrix and air conditioning evaporator I seem to remember.

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Old 21st April 2017, 18:11   #16
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It's more complicated than that, and no-one has succeeded in trying to work out exactly how the decisions are made in 'Auto' mode.
Wow!

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If I were you I would carry out the checks suggested to see if you can find a fault with your blower (ventilation fan) control.
I'll definitely do that.

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Not necessarily. It also depends upon the interior temperature of the car and there are also sensors on the heater matrix and air conditioning evaporator I seem to remember.
I was kind of supposing a perfect scenario where all of those were the same as the ambient temperature, but I should've made that clearer.*

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Note however that in cold ambient temperatures when you have selected heating, the blower (or ventilation fan) will notoperate until the coolant reaches a certain temperature. Is this what you're experiencing?
*Which brings me back to this The reason I was asking in the first place is that every setting has been above ambient temperature in Norway since october anyway, so I'm always using heating (unless the car is of a different opinion). And like I've said before the blower occasionally works immediately on cold days with a cold engine too.
Are you sure about the coolant thing though? I can't remember being in a car where the blower (the demist function in particular) doesn't work immediately upon starting the car, and on good days I don't think mine doesn't either.

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I prefer to investigate other options before checking/refilling the refrigerant, because that'll probably be £100 I live in Norway you see...
I thought £100 was a bit on the low side, but I didn't want to exaggerate. Turns out, it's in the £200-300 range How are British prices?
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Old 21st April 2017, 18:37   #17
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AC replacement in Belgium is 70 Euros.
So not too bad, your prices are ... Norwegian prices unfortunately.

There is a test on the AC system, have you done that? Perhaps is shows errors and that could be of help.
But AC systems need to be used and when old you are not getting away with topping up/replacement every 2-3 years (that is my frequency). Especially for the oil as that keeps the seals healthy (by using the AC at least every quarter but better every month to have 'fresh' oil keeping the seals in a good condition). Put it off too long and it won't work at all and repair is even dearer.

Nothing to do with the interior fan, but if the radiator fan is not working as is should, perhaps it can trigger what you are experiencing.
Don't think so as have no two 75 without AC and fans work as they should.

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Old 21st April 2017, 20:11   #18
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The two main sensors involved are the external ambient temperature sensor and the internal temperature sensor. If they aren't working properly it may explain a thing or two. I'd check the internal sensor first, afaik there isn't a way to find out what reading it's giving so it would be a substitution test. The external ambient temp reading should be displayed on the dash.
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Old 25th April 2017, 07:01   #19
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AC replacement in Belgium is 70 Euros.
So not too bad, your prices are ... Norwegian prices unfortunately.
Yep Apparently there's a ~70 € fee per kg of gas.

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Originally Posted by 350zwelgje View Post
There is a test on the AC system, have you done that? Perhaps is shows errors and that could be of help.
I don't know, what is the test?

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Originally Posted by 350zwelgje View Post
But AC systems need to be used and when old you are not getting away with topping up/replacement every 2-3 years (that is my frequency). Especially for the oil as that keeps the seals healthy (by using the AC at least every quarter but better every month to have 'fresh' oil keeping the seals in a good condition). Put it off too long and it won't work at all and repair is even dearer.
Mine's always in use, never off. Any drawbacks to that?

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Originally Posted by 350zwelgje View Post
Nothing to do with the interior fan, but if the radiator fan is not working as is should, perhaps it can trigger what you are experiencing.
Don't think so as have no two 75 without AC and fans work as they should.
From what I can tell my radiator fan is working properly.

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Originally Posted by Avulon View Post
The two main sensors involved are the external ambient temperature sensor and the internal temperature sensor. If they aren't working properly it may explain a thing or two. I'd check the internal sensor first, afaik there isn't a way to find out what reading it's giving so it would be a substitution test. The external ambient temp reading should be displayed on the dash.
Thanks, I'll keep that in mind External reading is fairly accurate, at least.
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