OT: fuel used by air conditioner

[alan_m]

My car only has a 1 litre engine and I only notice a slight difference I have to use on the throttle when pulling away from stationary, but my engine does appear to have 40 bhp more than yours.

[SteveW]

What car is it on? With my current car (Zafira 1.8, 140 BHP model) and my previous one (Focus 1.8 TDCi) the air-con switching in and out was noticeable as a blip in revs while idling, but unnoticeable when driving. I can't remember whether it is more obvious in my wife's car, with a smaller engine and lighter car, (Matiz 1.0) - and as the air-con in that failed years ago, I can't check.

[Scott]

It's a NIssan MIcra (1.2 litre), now 14 years old. When I push the AC switch I can feel some of the power being sucked away from the engine. There is a specialist near here with the diagnostic machine that sucks out the fluid, checks for any leaks and returns the right amount of fluid. Should I be paying a visit?

[SteveW]

If the A/C is producing nice cold air, I'd leave it alone.

[Dave Plowman (News]

The AC doesn't 'run' all year round. It cycles on and off depending on the temperature it is cooling and achieving. So in general, it will work harder on a hot day and use more fuel.

[alan_m]

That is the standard machine for topping up an air con. Before you go down this route check how much the extra top up gas costs. The machine will take out all the gas and register the amount BUT on refill it will put back the manufactures recommended amount which usually be more than that recovered. It could be expensive. If you AC is working satisfactory then probably leave it alone.

[mm0fmf]

No. You have a car that hardly had enough power to pull a greasy stick out of a dog's arse when new and is now quite old. It sounds like it is behaving just as a 14yr old gutless car with AC would perform.

[Scott]

Nice troll.

[Paul]

My first car only had 87HP on the engine. Then the engine, later in life, decided to have low compression in one cylinder. This is why it lacked power, and seemingly insignificant loads would upset it.

As far as AC maintenance goes, I believe in symptom based maintenance.

1) AC air no longer gets cold ? Get a recharge. 2) Check that electric fan on AC radiator is turning. It tends to run more continuously than the fan on the rad for the engine. An AC equipped car can have two rads and two fans. 3) AC rad has fins and air passes through. There can be impact damage and bent fins. If there was too much damage to the rad, it could no longer dump the waste heat. 4) Visually inspect compressor belt. It's one of the more long lasting belts. If it was frayed or it snapped completely, your compressor could be cooked, a bearing could have failed on the compressor, could be an issue with the compressor clutch. So compressor belt issue --> service.

But if you're getting cool air, I would not be visiting the specialist.

Any time you recharge a system, there is a small possibility of doing some damage or degrading the compressor while doing the work. The compressor is actually running, and working, while they fill.

When you recharge a system, a new dryer cannister should be fitted as well. The gas loop has the dryer cannister, so residual moisture that does not get vacuumed out during the refill, does not create "acid" inside the loop and corrode the metals in there. And it would be normal to change the dryer, when refilling.

When you get new AC equipment, and it is fully charged and the tech says it is ready, have a look where the "frost line" is. For example, when my central air was new, the line anywhere between the outdoor machine and the house wall, could have frost on it. This indicates the machine is operating properly. Most of the frosty line, has foam insulation on it to prevent losses, but three inches of surface is still visible for frost line check.

As of today, if I go outdoors, there is no frost on that line. Even when it was cool in the spring, there was no frost buildup during a test run. This indicates it's only half full of gas.

When the A-coil freezes up, now it's really getting low on gas. Ice on an A-coil is normal, but a large large buildup of ice is not normal.

So without using any "fancy gauge", or without screwing the dual gauge to the system, the owner/operator can have some idea of the relative state of the thing. My central air is not "broken", but it's "ripe" :-)

In a car, the moisture condenses on the element next to the cabin circulation fan. There will be a drain line from there, which just drips water onto the road. If you see liquid dripping from the car, and you've been using the AC, this is normal. If the car is dripping and you haven't been using the AC within the last few days, then it's time to do a fluid levels check on your chariot.

If the air in the car has an unpleasant smell, this can be caused by the same moisture that dripped on the road, plus any kind of air filter the car might have in that path. Some car designs seem to be worse than others, for this sort of thing.

Paul

[Tim+]

Just like a broken clock telling the right time twice a day, just occasionally a Troll speaks the truth. ;-)

Tim

[Jim Stewart ...]

fmf is an arshole not a troll...

[Jim Stewart ...]

no he is just an arseholl trolls can be nice

[Paul]

On a fancy car, the car comes with a "climate control system". The best scheme would be "climate control system with multiple zones", where the front seat can be cooled to 27C and the back seat cooled to 25C. And the AC will cycle on and off, while maintaining the two temperatures selected by the (multiple) users.

On a cheap four-banger, there is no climate control. Just a fan knob. If the fan knob is on, and the AC button (blue status light) is on, then the AC runs continuously. If you switch the fan back to off, the AC goes off.

The one dispensation a four-banger will have, is there is a thermistor to check for "dangerous operating condition". The car will not allow the compressor to run, if there is a chance liquid refrigerant will enter the compressor. If the cabin temperature is low enough, the attempt to start the compressor will be gated off by the car. This is why, for most of the winter, I cannot attempt to "lubricate the seals" on the AC. I would need to be in a heated garage to complete the procedure for that.

The nice thing about the four-banger, is the control is visceral, there is no attempt to hide how it works, and the user has a very good idea whether energy is being wasted or not. If the AC button with the blue status light is off, then the AC will not be engaging. And if you want a more iron-clad deal than that, you could pull the fuse for the AC relay in the panel. And then the car can no longer operate the clutch on the compressor, and the clutch remains disengaged. If you suspect the compressor bearing is shot, then having someone remove the AC belt would be in order. If you wanted to decommission an AC, that might be the easiest step (as then it cannot interfere with vehicle operation).

Paul

[Paul]

Is your secret weapon a turbocharger ?

Paul

[Scott]

Well ... I have learned from the thread. There are other threads that are of no interest to me but I don't object to their presence.

[alan_m]

Not always true. I've had Ford Focus where when you select the option to direct the fanned air to the windscreen the AC automatically comes on to dry the air for demisting purposes. The AC light does not come on in this situation. Both my Focuses have had heated windscreens so this fan blower setting is rarely used.

[alan_m]

It does have a turbo

[Rob Morley]

No need, it's exhibiting normal behaviour as long as the aircon cools the car. We had a 1.0 Micra, a useful little town car but it wasn't happy on motorways, and up hills you had to drop a gear and thrash it to maintain A road speeds.

[John Rumm]

Much depends on the aircon in question. Not all have the same power input requirement, the same aircon performance, or the same cabin space to cool for that matter.

First car I had aircon in was a 2L injected engine, but the aircon sucked about 10HP - that was enough you could feel a small difference in performance - and it was enough to introduce a slight "jolt" as it cycled on and off when creeping along in a traffic jam.

Sprog 1's car is a 1.3 Micra n-Tec, and the aircon on that draws significantly less power - so the effect on performance is not particularly noticeable. Its also a small light car with a fairly small cabin area to cool.

My current car has a fairly powerful aircon, but you don't notice it at all. (combination of being an auto with a torque converter, so a slight "smoothing" of the drive, and enough power that 10hp here or there is not going to be felt!)

[Andrew]

I didn't use the aircon on my 1998 Astra F for years. Previously when pressing the aircon button there was a clunk from the magnetic clutch and the engine idling note changed as the engine worked harder.

When I pressed the aircon button having not used it for many years the engine almost stalled, then there was a loud bang from somewhere near this pulley and the aircon never worked again !.