Citroen c5 2.0i 16v AUTO (al4) brakes!

[thundermaster]

A strange thing:

With a/c on, there is no hydraulic assistance on brakes in slow speeds (20km/h), so I have to hit the brake strongly in order to catch. Brakes are OK when speed is higher. This happens also on reverse.
With a/c off, things looking ok. The car is 2.0i exclusive and it is auto (al4).

Any ideas about this?

Thanks

[GiveMeABreak]

The A/C has nothing to do with the braking circuit, only in that when operating it puts a bigger strain on the engine, so at lower speeds the engine power may reduce slightly which may decrease the vacuum in the braking circuit. Obviously more noticeable at idling or low speed, where the auto gearbox is 'coasting' as it were, when no power is required as is when slowing down.

[thundermaster]

Thanks Givemeabrake!

The car was not used for some time, before I bought it. I think that changing brake fluid is a very good idea and may solve this issue!

[GiveMeABreak]

Ideally the brake fluid should be changed every 2 years. Make sure that you have it done properly as the system needs to be bled on both circuits - the braking system and the ABS/ ESP hydraulic block, so will take 2 people and a diagnostic tool like Lexia / Diagbox to do the Hydraulic block.

I'm not suggesting this will be the fix, but if you suspect the brake fluid is a lot older than 2 years, then it will need doing in any case as a priority.