Holeshot Posted December 13, 2009 Share Posted December 13, 2009 Does anyone know how to avoid the air con unit raising the revs? They tend to go up and down periodically when it's turned on, I don't know if thats normal or not! Quote Link to comment Share on other sites More sharing options...
kjgreen3 Posted December 13, 2009 Share Posted December 13, 2009 Should be normal as long as the revs dont go above say 1500-1600 rpm. When under extra load the ECU will increase the revs to match demand and to prevent stalling. When your car is warm see what it idles at, turn your full beams on and you should notice a slight increase in revs as the alternator has to work harder to power these accessories. This is the same for the air-con when its switched on although it saps a lot more hp when its working hard. Anyway this time of year you shouldn't be having it on lots its freezing out! You only need to switch it on for 20mins once a week or so to stop the seals drying out. Quote Link to comment Share on other sites More sharing options...
Holeshot Posted December 13, 2009 Author Share Posted December 13, 2009 I find I need to keep it on most of the time to avoid the screen fogging up, of course I can just keep the window open. From what you've said about it being alternator related, perhaps an upgraded alternator would mean that it doesn't need to increase the revs? It doesn't go particularly high I just don't like it jumping up suddenly when I'm sat at traffic lights etc. Quote Link to comment Share on other sites More sharing options...
kjgreen3 Posted December 13, 2009 Share Posted December 13, 2009 Sorry I wasn't very clear when I last posted. The air con unit is a separate entity, its about the same sort of size as the alternator but its on the right hand side at the front of the engine (as you look at it). I was using the alternator as a reference to the fact that the engine revs up when you increase the 'load' upon it. The alternator drives all the electrical accessories and keeps the battery charged up it has nothing to do with the air conditioning (except powering the fan/blower motor). Its the actual air-con pump that causes the revs to rise when you turn the air-con on. You could turn the air-con off when driving and turn the heater onto cool/warm/hot air and use that to keep the windows demisted. Also you will see an increase in fuel economy as the air-con saps engine power so you burn more fuel whilst idling and driving about it may be a couple of miles to the gallon, but don't quote me on that. I sometimes use the air-con to fast demist the interior windows when I first start the car on a cold morning but when the engine warms up I switch to the standard heater blower. This would stop the erratic revving as the heater doesn't cause anywhere near the same loading on the engine as the air-con does. Quote Link to comment Share on other sites More sharing options...
devan Posted December 13, 2009 Share Posted December 13, 2009 Air-con only revs about 300rpm more than usual doesn't it? Cant understand why its an issue, its just the car doing its job lol. Quote Link to comment Share on other sites More sharing options...
Dave17 Posted December 13, 2009 Share Posted December 13, 2009 Air-con only revs about 300rpm more than usual doesn't it? Cant understand why its an issue, its just the car doing its job lol. Exactly! It's not like it's going to cause you to surge forward in to the car infront. If you don't like it don't use aircon. Quote Link to comment Share on other sites More sharing options...
Holeshot Posted December 13, 2009 Author Share Posted December 13, 2009 It's not a major issue... If I could of got rid of it then it would have been a minor improvement in an otherwise happy drive. The Supra's not quiet and I wonder what it sounds like from the outside when you're sat at the lights and suddenly the revs go up, then down, then up etc. Thanks for the effort on the detailed response kj. Quote Link to comment Share on other sites More sharing options...
devan Posted December 13, 2009 Share Posted December 13, 2009 Its a sound described as ..... sweet Quote Link to comment Share on other sites More sharing options...
Konrad Posted December 14, 2009 Share Posted December 14, 2009 I find I need to keep it on most of the time to avoid the screen fogging up, of course I can just keep the window open. If you need to switch on AC to keep your windscreen from fogging, your air circulation is set up to internal one. Set it up to external and switch on fan to full power - screen will defog in no time without AC help, then lower fan rpms. Quote Link to comment Share on other sites More sharing options...
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