Problem Audi A4 1.9 TDI heating installation glow plugs



I also have a problem with the glow plugs from the heating system, the ones on the part behind the cylinder head. When I start the car, there is no current on them. In 10 seconds, current comes on the middle one, only the middle one. After 20 seconds it it stops the current on the one in the middle and it comes to the ones on the sides, or rather the top and the bottom. When the water reaches 40 degrees, the current on the sides is cut off and only comes to the one in the middle. When the water reaches the at 45 degrees the current is cut off.

Does anyone know what I need to check and especially how it should work exactly?

I could connect them together and regardless of which current comes, they will all be powered. The problem is that up to 50 degrees, the plus is cut, and then it will be difficult to heat up. Up to what temperature are they powered?