PSA Climate Control Op-Amp

[addo]

This is an interesting one; I don't know how far the issue spreads but probably across all '90s PSA cars with the electronic temperature mixer.

Paris the 405 had developed the inevitable "bumblebee in a matchbox" or stripped gear in the mixer flap motor. I traced the root cause to an ill-fitting flap in the heater box, and rectified. The stripped gear was replaced in the motor housing.

On a hunch I checked out the climate ECU. This is one of the more ordinary ones; incoming air temp, dash level air temp, evaporator core temp are its sensory inputs and the only mech drive is its temperature flap. In attempts to power this mixer flap, the op-amp had cooked pretty well - six of its eight legs were dry in their eyelets or barely surrounded by gritty solder. An adjacent resistor had felt the heat too, with its closest end being dry jointed.

Luckily for us, the L272M op-amp is still common enough and cheap - if one believes the internet. I'm hoping the combination strategy will resolve some of these niggles for a good while.

[addo]

One for the overclockers among us:



(Yes, the mod is real... )

I also inserted a little slip of closed cell foam sheet into the case rear, to stop the PCB rattling.

Anyhow, the points of order are:

1. If your flap motor strips a gear, it's working too hard. Dismantle heater box and fix the obstruction.
2. If you persist without relieving this extra friction, it will cook the driving circuitry to some extent.
3. If you roger the climate module, the Bitron fan controller will not work as required in regards to the aircon.