Revs Dropping With Air Con Activated

[AnthonyP]

Hi all,

I have just joined to ask this really as we have never had a problem with the RAV for nearly 7 years of motoring! Incredible cars.

It's a 2003 2.0 vvti auto and when the air con is turned on the revs drop drastically and it almost dies. Then it changes and the revs return to normal. We opened the bonnet and heard a clicking noise when the rev drop starts. It seems in some way related to the fan that activates to keep it cool during air con use. Is this a known fault to anybody?

As I said we have never had a problem with the RAV so we don't have a workshop manual for it or anything like that. I run a 1987 Mini myself so am no stranger to working on cars, so if it is a small problem I might be able to do it myself.

Thanks for reading.

Kind regards,

Anthony.

[Davrav]

Hi all,

I have just joined to ask this really as we have never had a problem with the RAV for nearly 7 years of motoring! Incredible cars.

It's a 2003 2.0 vvti auto and when the air con is turned on the revs drop drastically and it almost dies. Then it changes and the revs return to normal. We opened the bonnet and heard a clicking noise when the rev drop starts. It seems in some way related to the fan that activates to keep it cool during air con use. Is this a known fault to anybody?

As I said we have never had a problem with the RAV so we don't have a workshop manual for it or anything like that. I run a 1987 Mini myself so am no stranger to working on cars, so if it is a small problem I might be able to do it myself.

Thanks for reading.

Kind regards,

Anthony.

Welcome to the club Anthony.

I have no idea if this is related but there was a similar issue raised here recently:

LINK

Hope you get it sorted.

David

[anchorman]

Welcome to the club Anthony.

I think this is perhaps a bit different than the one that Dave has compared it to in that this one you get the problem at idle and is specific to the A/C.

The noise you hear is the compressor clutch operating and is normal. If you look down at the compressor while the engine is running you will see that the pulley is stationary but if you get somebody to switch on the A/C or just let it cycle you will see that the clutch engages and the pulley begins to turn. However, the load on the engine when the compressor kicks in is significant and is quite capable as you say of nearly stalling the engine and this is catered for by a function called "idle up". Some of the heavier loads on the engine send a signal to the engine ECU that causes it to counter the load by increasing the idle speed. You may have noticed in the past that if the A/C was switched on and the engine was idling you would hear a click of the clutch engage combined with a slight revving of the engine.

It seems that this function isn't working on yours. If you look at the manual fault finding chart here you will see it at the bottom of the first page;

m_ac_0003.pdf

I am assuming that your 2003 model is with manual A/C and the control it refers to is simply the switch. You will see at the other end of the scale is the engine ECU and you don't really want to start playing with that unless you really have to. So! If I were you I would first try to identify if "idle up" was working and the easiest way to do that is by standing the vehicle on the road side with the engine idling and now activate idle up with the power steering. It may work just by easing to one side with the steering wheel with just enough effort to move the road wheel slightly but not actually turning. If the engine doesn't pick up (watch the rev counter) move the vehicle so the road wheel is close to the kirb then turn the steering wheel so it turns up to the kirb and then resists you doing it any more. If "idle up" isn't working it will slow the engine down to near stall speed again like with the A/C. In that case I would say it is the ECU as you are signalling it from a seperate source but if it does pick up and doesn't attempt to stall you are in the clear!

The next easiest thing to check is the A/C switch itself. If you remove the switch panel you might be able to fix it by just giving it a good squirt with some electrical contact cleaner or at worst substituting another switch (do you know someone with another Toyota that will oblige just to take it out of the equation? - other Toyotas may have the same switch). If not you can probably get one from a breaker or our resident parts man Kingo will sell you one at a discounted rate and post it to you.

Next thing is the A/C amplifier which amongst other things has to relay the idle up signal from the switch to the ECU. Again I would go for a scrappy or "Findapart" as that could be expensive.

Here is the info for locating and removing the parts so if you are used to fiddling with Mini's (I had loads of them when I first started driving and so am used to what a fiddle they can be) you should be able to get to the bottom of this errant A/C!

Good luck.

ac_amp.pdf

ac_panel.pdf

components_ac.pdf

[igormus]

Hi all,

I have just joined to ask this really as we have never had a problem with the RAV for nearly 7 years of motoring! Incredible cars.

It's a 2003 2.0 vvti auto and when the air con is turned on the revs drop drastically and it almost dies. Then it changes and the revs return to normal. We opened the bonnet and heard a clicking noise when the rev drop starts. It seems in some way related to the fan that activates to keep it cool during air con use. Is this a known fault to anybody?

As I said we have never had a problem with the RAV so we don't have a workshop manual for it or anything like that. I run a 1987 Mini myself so am no stranger to working on cars, so if it is a small problem I might be able to do it myself.

Thanks for reading.

Kind regards,

Anthony.

Hello Anthony

The topic you criated is very interesting.

All my trials were for nothing to get cross section drawing of the compressor. This could reply all questions.

As for the disigned construction, and as was investigated by me -- this compressor is normally idle rotated driven by a belt without any electro magnetic coupling (it is not available)

The 134a gas is not transfered/pumped unless you push the ON buttom on the climate control panel. Once pushed the el signal gooes to solenoid valve mounted in the compressor body -- resulting this valve closes small circuit (comressor to compressor) and opens a big one (compressor --> condenser--> thermo expansion valve --->evaporator ---> compressor). The one of the reasons might be with this solenoid valve faullt (?) There might be a blocade before throttle valve in case there are water vapours in the system -- resulting the compressor can not compress this gas endless. There might be another problems - wait for posts from forum.

Cheers/Igor

[AnthonyP]

Fantastic replies guys! Very interesting stuff. I'll try what you suggested and post the findings.

Many thanks,

Anthony.

[igormus]

Fantastic replies guys! I'll try what you suggested and post the findings.

Many thanks,

Anthony.

yes , Anthony

onething else -- as far as i understand the thermo expansion valve gets special el signal from ECU as to what 134a gas boiling temperature must be in evaporator. This is understood deppends on both outside temp and saloon temp (differential signal). The another problem might be with this throttle valve that is either faulty or gets a wron sygnal. You have to examinate it, as well.

Cheers/Igor

[AnthonyP]

anchorman, on the first pdf you provided it refers to a page AC-32, but it does not have this page included. Do you have this page available?

Many thanks,

Anthony

[anchorman]

Well yes but it doesn't tell you a lot.......

m_ac_0032.pdf

Let me know if you think anything else would help