Thread: Loss of power in D2 when aircon switched on?

Hey Mick,

The reason it puts a load on the engine, is that when you turn it on, it engages the clutch on the front of the compressor that is driven by the serpentine belt. This then takes x amount of power to work.

Nanocom is always available!

Rgds
Pete

I would say the aircon is highlighting an underlying engine problem. I had a similar experience in an old tdi D1. In this case the injector pump required recalibration.

I suggest you get it professionally diagnosed.

Cheers

Is it possible the extra current drawn by the A/C is causing a voltage drop and affecting the ECU. Perghaps there is a earthing issue somewhere.

An ac typically draws about 7hp when the compressor is engaged so it could be that, that you are feeling, you cant really notice it in a V8 but I have had nothing to do with the diesel so I cant tell you if it is normal tp be noticable.

Blythe

Hi Mick I am also interested in this because I have what may be a similar problem. There is a definite draw on engine power with a/c on in any car but I have noticed something peculiar on the TD5(DII). If I drive with the a/c on and check engine variables with the Nanocom I notice that although coolant temp is not being affected I am running an air inlet temp at least 10 degC higher with a/c than without. When outside temp is nearer 20 this is not an issue. However on a warm day around 30 deg the air inlet temp gets to 60 degC and there is a considerable difference in engine performance and note. I have got to the stage where I recognise that the high air inlet temperature coincides with poorer performance but I have not got further than that. Any one with any ideas?

Originally Posted by Panya

Hi Mick I am also interested in this because I have what may be a similar problem. There is a definite draw on engine power with a/c on in any car but I have noticed something peculiar on the TD5(DII). If I drive with the a/c on and check engine variables with the Nanocom I notice that although coolant temp is not being affected I am running an air inlet temp at least 10 degC higher with a/c than without. When outside temp is nearer 20 this is not an issue. However on a warm day around 30 deg the air inlet temp gets to 60 degC and there is a considerable difference in engine performance and note. I have got to the stage where I recognise that the high air inlet temperature coincides with poorer performance but I have not got further than that. Any one with any ideas?

Air at 60 degC will be less dense than at 30 deg C so less oxygen so less power. The ecu also looks at the difference between the ambient temperature and the inlet air temperature and will reduce the power output when there's too much difference. As the A/C condensor is in front of the intercooler, the inlet air will always be hotter with the a/c working, especially on hotter days when the a/c is working harder.

I noticed considerably less performance degradation on hot days when a bigger I/C was installed (done pre-chipping), to the extent that it went as well (a/c on) on hot days as cool days.

Thanks for all the replies guys. Adding a bit more info, with my A/C on I also notice an increae in EGT's and exhaust noise as the engine seems to have to work much harder to simply drive. I drive many other cars regularly (including a TD5 90) and do not have this problem on any other car....mine is the only car I you can actually feel the difference in performance and drivability.

Aye, Mick

Originally Posted by MickG

Thanks for all the replies guys. Adding a bit more info, with my A/C on I also notice an increae in EGT's and exhaust noise as the engine seems to have to work much harder to simply drive. I drive many other cars regularly (including a TD5 90) and do not have this problem on any other car....mine is the only car I you can actually feel the difference in performance and drivability.

Aye, Mick

It seems odd that the effect is so noticable. You may want to have the AC running pressures check, typical systems running in your temperature zone would be at about 220 - 250 psi, maybe a little lower.

A high engine draw would indicate to me that maybe the pressure is running much higher than that !

How clean is the condenser ?, are the condenser fans running ? are they running the right way ? (yep I know this sounds silly, but I have seen it more than once).

A quick check, run the car, switch on the AC - observe the conditions, then get a garden hose, and spray cold water on the condenser coil and see if the engine drain seems less, if it does this will indicate high pressures in the system.

High pressures are caused (generally) by

1. Poor condensing, blocked or dirty condenser coil, poor condenser fans
2. Refrigerant overcharge
3. A blocked or semi blocked filter / drier, or a blockage somewhere else in the system.

There are a few other areas that can cause this, like faulty TX valve, but the above are the main ones.