Well I finally got chance to fix the heater flap diaphram today.
To recap when my car was remapped it was identified that the varioram system was not activating. The failure was due to a faulty part of the heating system ie there is a vacuum system which operates both the varioram and a a rear heating flap. The rear heating flap is activated by a solenoid which when triggered opens to allow the vacuum to operate a flap via a diaphram. I had a faulty diaphram. This would not normally cause total failure of the varioram as the solenoid would isolate any leaks on the heater side until it was activated but to compound matters my solenoid was also faulty (effectively always open). This meant that the vacuum system effectively had a permanent leak and so the varioram part of the system could not get enough pressure to activate when needed. It is possible that the solenoid failed first and this caused the diaphram failure but I believe the diaphram is a common part to fail.
The heating flaps default position means that air is drawn into the heating system via the engine (ie warm) as and when needed. However there are two reasons why the solenoid may be activated to open the flap to bring in air from outside (via the engine grill) rather than from the engine:
- Used when engine air gets too hot and cooler air is needed.
- When reverse gear is selected. ie the grill intake is higher reducing the chance of exhaust gases being drawn into the heating system.
Neither of these functions are critical and this part of the system can be removed meaning that air is only ever drawn in from the engine (ie a different intake tube can be fitted without the flap etc....)
Therefore as a temporary fix the solenoid was replaced with a replacement part (FOC as they had one spare at the garage on the day of the remap) and the electical connection was disconnected to prevent the solenoid from opening and causing a pressure leak via the faulty diaphram ie meaning that the varioram system worked for the remap.
So down to replacing the faulty diaphram.
Here is the part. I can't remember the exact price as I bought it some time ago now but it was c£50.
The first thing that I noticed was a change in design to the old part ie the activating rod with ball joint is a fixed length. On the original it is two piece allowing the length to be varied. This did not cause any problems as the set length was fine when fitted.
Here is the original in place (spot my winter job to clean the engine now that I have fixed the spoiler wall)....
It is a simple yet fiddly job to remove and replace. There are two hex bolts that need to be unscrewed. However they are accessed via the side and certainly if you have varioram and air con pipes they get in the way. You need a small hex key (or cut an old/cheap one down). You need to feel the key into place blind to undue the bolts (nb putting them back seemed much easier). Tip: place a cloth under the part as its so easy to drop either the hex key or bolts down into the engine and they are a nightmare to get out (ask me how I know!).
Once these two bolts are removed its simply a matter of removing the top vacuum hose and cracking the ball joint at the bottom of the lever.
Here are the parts exposed and you can clearly see the lever that operates the flap in the heater inlet tube to divert airflow from engine to grill intake....
Fitting is the reverse and seemed a lot easier / less fiddly. Job done.
Here is a video of the fresh air flap now working properly. The test is carried out using my Bosch "Hammer" diagnostic tool. The ignition is on which primes the vacuum system and you can use the "Hammer" to switch the flap to the two positions on command. You can actually hear the flap flip over and then see the push rod moving....
ps you could do the same by getting someone to sit in the car and switch from 1st to reverse gears :wink:
click on pic for video link