I think I have problems with the inside heating-cooling unit.

In winter, it's OK for about 10 minutes, and then the heater kicks off - the air inside the car is really hot.

In summer, cold air blows for about 10 minutes too, and after that, warmer and warmer air starts to blow...

What do You think is the problem? Or is this common for a Felicia?

Can I somehow regulate the heater (apart from the button on the board inside)?

If the heater valve works the same way the Favorit one does I guess the seals in the control valve have gone or the valve itself is broken. The other possible cause is that the heat control inside the car has at some point become detached from the valve on the heater, try get someone to move it left to right while you look under the bonnet from the right hand side of the car where the heater matrix is at the back.

Is the heater matrix on a Felicia ever isolated from the cooling system? When I replaced the matrix on my 1.3 it didn't seem to have a valve. I got the impression it was just the air flow that was closed off with a baffle. When it started to leak I had to bypass it until I could get a new one as it never closed off even with the heater on cold. Sounds odd so maybe I'm wrong.

It was easy to bypass the matrix by unplugging the hose ends and connecting them with a short length of hose. This could be a short term fix to get you through the summer.

So, is bypassing the matrix an easy task? Will some liquid spill out when I take the hoses, or... ?

As I remember, I used a piece of plastic hose, the type with nylon brading inside. This was a snug fit in the hose and rigid enough to tighten a jubilee clip onto. I can't remember how long or if I bent it into a U or used the flex in the heater hoses instead. Both the in and out hose ends face the same way so somehow they have to turn. They are easy to see and get to though.

It was a while back now and just to tide me over until the new matrix was delivered (turned out to be a few weeks).

If you've got the hose cut ready to go in and you're quick you won't lose too much coolant as you're quite high up in the system but you'll need a top up bottle.

Does anyone else know if there is actually a tap in the circuit to save you the hassle? I never found one but someone else may know.