So I tore apart the interior and found an air line disconnected under passenger side rear floor. I reconnected it and pump runs but wouldn’t build pressure. I disconnected the vacuum return line from pump and noticed I couldn’t suck air from that line. When I leave it disconnected the pump runs and now builds pressure and seats work. I assume I shouldn’t leave the line disconnected but any ideas why it would be blocked? “Can’t suck or blow air in that line.

the picture below is the line that was disconnected under the floor inside car. Which I believe is the vacuum return line

 

I'm going to leave this right here. https://w220.wiki/Pneumatic_System_Equipment_(PSE)

Not sure if it's going to help resolve your issue but may help with a better understanding of the system.

This will help understanding the routing if the link works

https://nemigaparts.com/cat_spares/e...220174/66t/80/

 

Thanks that definitely helps. I’m thinking one of the vacuum switches must be set to pull vacuum and it can’t or shouldn’t be. I have unplugged the pump several times but never the fuse yet. I would think the vacuum return line has to be able to switch between vacuum when needed and being able to sucking fresh air somehow or the pump could never build pressure.

or maybe I’m still missing something

 

If you're up to pulling your PSE pump, aka central locking vacuum pump, it may be worth a look inside. Untreated vacuum leaks can lead to overheating the motor inside and melting the plastic manifold within that contains the flow paths to your lines. There are also solenoids coils, a couple circuit boards and a lot of solder points inside that can fail as well. This quickly turns into how far do you want to go down the rabbit hole if you don't have SDS at your disposal to troubleshoot malfunctions.

If the pump itself is a problem, you can try to repair it in some cases, gamble on buying used ($200-ish) or buy new ($600-ish). From what I've read , I believe these need to be reprogrammed when replaced as well. This weekend I'll be replacing a pump motor with a new one ($60) and utilizing a used manifold from a bad ebay deal. The key to success is mitigating any vacuum leaks in your system to prevent excessive pump run time, prior to replacing the pump. I believe you can also adjust your pump run time and it's explained in the W220 wiki PSE section. If my repair doesn't go as planned, I'll suck it up and buy new and just chalk it up as a learning opportunity.

My trunk release actuator had a massive leak, the line to my dynamic seat pump had a split (which also had a burned out motor) and my central locking pump manifold was melted with a failing motor. So FWIW, you may have several issues that you haven't diagnosed yet.

I'll try to document what I do in case its of use to anyone. I'm sure this topic has probable already been beaten to death over the past 20 years.