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760 1986 ACC Temprimental

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Old Sep 18th, 2019, 08:15   #1
Volvo760AF
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Default 760 1986 ACC Temprimental

Have ACC and now in the mornings I find it only works on Max blower (far right hand setting). The rest do not work. Then, after I've been driving for a little, they all work again. Is this normal or something that can be addressed? Thanks.
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Old Sep 18th, 2019, 09:53   #2
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Just to clarify, do you mean the compressor only cuts in when you select maximum fan and defog to the screen? All other heater functions still work as they should?

It sounds on the basic information you've given that the A/C is working correctly, if you read the Owners Manual (supplied with the car when new) about the A/C, your questions may well be answered.

There are certain parameters the A/C system follows and it measures the temperature in the cabin - it won't cool an already cold car but will supply heated, conditioned air to the screen for defogging purposes as it's much quicker than hot, unconditioned air due to removing the moisture that's naturally present in fresh air.
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Old Sep 18th, 2019, 14:13   #3
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As in it only works on the far right hand setting upon starting. Shortly into journey all others will work
. If that's normal then no worries. I'll check the manual as stated. Do you know if the air con can be recharged or rejuvenated in anyway. It blows cool air but not great. What would I be asking at a garage?
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Old Sep 18th, 2019, 15:27   #4
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Quote:
Originally Posted by Volvo760AF View Post
As in it only works on the far right hand setting upon starting. Shortly into journey all others will work
. If that's normal then no worries. I'll check the manual as stated. Do you know if the air con can be recharged or rejuvenated in anyway. It blows cool air but not great. What would I be asking at a garage?
As in what only works on the far right? Far right of what? I'm not familiar with the older ACC system, never had one, never had to work on one.

Does it have an "Auto" button? If so, there's every chance that even in manual mode, it will not let the blowers work at full speed until the engine has warmed up and so has the car.

To give you an idea, these are my controls :



As you can see, nothing has a "far right" setting and i've seen many different heater/air-con controls in many different Volvos so it's not a case of being unnecessarily picky, it's a case of please be more specific so we know what you're referring to.

In mine, the fan generally stays on auto, the direction controls on the floor and vents and the temperature according to how i feel on a particular day/time. When i first start, the fans don't usually start for a couple of minutes unless the car has been sat in the sun and is hot inside, even then they ramp up over the course of a few seconds. On a cold, dull day, they start slowly and stay there until it's warm, depending where the temperature is set.

That's how most Climate Control systems work, whether in a car, house, office block or wherever. Might vary in certain details across the board but a rough rule of thumb is along those lines.

Also a couple of other points to remember about air-con. First is it isn't "instant freeze", remember the gas in the system takes time to cool the air in the cabin and indeed pull the temperature inside the heater box down, much like your fridge at home takes time to pull the temperature down after a power cut.
Second, whether you have R12 or R134a (it may have been converted, mine has but mine isn't fully functioning at present due to misdiagnosis by the previous meaning the evaporator was removed! ) it will still only reduce the temperature of the incoming air by about 10C so if it's 20C outside, you'll get 10C out of the vents unless on "Recirc", if it's 30C outside, you'll get 20C and so on.

Also as previously mentioned, conditioned (dry) air defogs the screen much more quickly so with the highest temperature and screen selected, you should get full fan spped fairly quickly - all other temp settings are likely to inhibit the compressor and reduce the fan speed until warmed up.

As for going to a garage, don't! Find a recommended air-con specialist in your area.

If it's still R12, most garages will firstly refuse to work on it because they can't and secondly, it will need converting to R134a instead.

This involves a full evacuation of the system, new valves for the R134a gas (sometimes referred to as "Service Ports" - normally they just screw onto the old R12 ports), possibly a reciever/dryer change (but i think you just have an accumulator, same as me), new, different oil for the compressor introduced with the R134a gas when it's recharged and a full system check.

If it's already been converted to R134a, chances are you'll just need a regas. This is simpler as the system gas is removed, system vacuumed down and checked for leaks then new compressor oil and gas introduced to give it a full fill.

This will be a different amount of gas to what the R12 quantity would be due to different densities of the two gases. If memory serves, R134a is about 20% heavier than R12 so if it took say 1000g of R12, it would need 1200g of R12 for the same fill in terms of volume and thermal properties.

The big thing with air-con is "use it or lose it" - most people who know this leave it on auto and just select the temeprature and where they want the air to go to. Even if you use it minimally, make sure you run it for at least half an hour each month to keep the seals from drying out and leaking.

As for the age-old myth that it uses too much fuel The drag created by driving with the windows open uses more fuel than using the A/C with the windows closed - it's quieter too!
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