How much does the ac affect your subie

on my 2.2 when the ac is on i get a rough idle and quite a noticeable reduction in power when the a/c kicks in and out. I believe this to be related with outside temperature (only a hunch) so when its warmer out the ac takes more power out and a rough idle leads me to believe ac pressure excessive when its hot?

all service items have been done including iridium plugs and msd coil and NGK leads

no difference before or after service

ive cleaned the MAF sensor but not the IAC valve yet

any help will be appreciated thanks

On my 96 L I noticed the AC kick on and the power was greatly affected. With my 99 LGT it isn't as bad but still noticeable. They are probably the worst with power loss in any car/truck I've ever owned and I've owned a lot of different cars throughout the years.

Also on my 96 L when I would be at a stop light I would get a weird vibration and it was worse with the AC on. I don't feel that vibration on my 99lgt but being an auto mechanic and working on many Legacys the earlier second gens seemed to all have that weird vibration while at stop lights. They also have this shutter in the steering wheel when going up or down approaches, it was something to do with the power steering hose being an inadequate size as per a TSB Subaru released.

It does drop the idle a bit in mine. It really does seem to put quite a load on the engine. I tend to turn the A/C off when climbing steep hills or pulling into traffic because it makes that big of a difference.

This thread got me interested so I got a little data on it from my car and a diagnostic tool. This info is from a stock 98 LGT with the 2.5. All measurements were taken at idle and AC measurements were taken when the compressor was running.

 

RPM:

687 RPM - NONE

862 RPM - AC

175 RPM - CHANGE (25%)

 

Horsepower:

5.00 HP - NONE

5.25 HP - AC

0.25 HP - CHANGE (5%)

 

Fuel consumption (gallons per hour):

0.32 GPH - NONE

0.48 GPH - AC

0.16 GPH - CHANGE (50%)

Yeah, the AC is a hog, especially on the L model. Sometimes, as stated above, I'll turn it off if I need extra power. Most of the time I don't worry about the power loss .. I'd rather have the cool air.

Hello;

When the A/C is turned on the idle should automatically bump up a bit to help with the load on the engine. Besides the pump working, alternator is turning harder to keep up with the current demands of the interior fan, A/C fan, and clutch. If you have a friend with HVAC gauges, have him check the low/high side pressure. Sounds to me that your system is overcharged, causing the pump to work harder. Steven.

Would the A/C compresser come on wither there's a/c in the system or not?????

Would the A/C compresser come on wither there's a/c in the system or not?????

 

Yup, even if it's cold it will turn on. A/C also dries out the air in the car so sometimes it's needed when it's cold out so you can defog your windows.

Hmm it sounds like my problem maybe normal although i think the idle is a problem it is quite violent at times. Yea ill get the ac pressures checked out and ill clean the IAC valve because i get no increase in idle speed with the ac on in gear it seems to go lower than normal but when its in park the idle seems to increase with the ac on.

Would the A/C compresser come on wither there's a/c in the system or not?????

 

Yup, even if it's cold it will turn on. A/C also dries out the air in the car so sometimes it's needed when it's cold out so you can defog your windows.

 

Uh what? That answer had nothing to do with that question...

 

I'm pretty sure that DGR was asking if the A/C compressor still activates if there is no Freon in the system.

 

The answer is no. There is a pressure switch that cuts the A/C system electrical circuit when there isn't enough pressure to operate safely.

Uh what? That answer had nothing to do with that question...

 

I'm pretty sure that DGR was asking if the A/C compressor still activates if there is no Freon in the system.

 

The answer is no. There is a pressure switch that cuts the A/C system electrical circuit when there isn't enough pressure to operate safely.

 

 

 

So if I put in the Freon it should work correct????

Uh what? That answer had nothing to do with that question...

 

I'm pretty sure that DGR was asking if the A/C compressor still activates if there is no Freon in the system.

 

The answer is no. There is a pressure switch that cuts the A/C system electrical circuit when there isn't enough pressure to operate safely.

 

Wow, I can't read good lol. For some reason I read "would the a/c system come on in the winter"

 

Disregard my post

So if I put in the Freon it should work correct????

 

As long as the rest of the electrics are good, and the switch works, and there are no leaks, etc...

 

I would fill it up and see if it works. If it does, take it a to a shop so that they can fill it properly. There needs to be a certain amount in the system and the moisture in it needs to be removed if it was empty and/or exposed to the outside air.

^ I was thinking the same thing as what Kenny wrote.

 

I would add that you should make sure that the freon has a dye in it in case you need to locate leaks.

I used my AC for the first time today and I was surprised how much power I lost. On all of my previous vehicles (Oldsmobile, Pontiac, VW, Toyota) I barely noticed it.

Would the A/C compresser come on wither there's a/c in the system or not?????

 

if you mean coolant in the system, i dont think it will. most cars are fitted with low pressure sensors that will lock out the compressor.

I ripped out the a/c pump and whole system minus electrical controls and when I hit the a/c button (that does nothing) it still kicks it into high idle.

 

The a/c button has now been deemed "vtec mode" ha

I ripped out the a/c pump and whole system minus electrical controls and when I hit the a/c button (that does nothing) it still kicks it into high idle.

 

The a/c button has now been deemed "vtec mode" ha

 

Haha I like my air con way too much to remove mine

Mine never worked

With a/c off my car gets -20.2in/hg vacuum. On its around -17.5in/hg. So it is definitely taking some of the engine power away.

 

If your car has lower compression or anything else wrong with it turning a/c on exaggerates the problem.

 

 

You can change every serviceable item but will never really know if your engine is in tip top shape until you compression test it. I personally will never buy a car without testing it.