vacuum reservoir
 

Still trying to resolve a "no heat on highway" issue"
Checking vacuum. Reading the climate control manual says to test the valve before the 3 way connector then to test the red vacuum line with the gray stripe. The valve holds vacuum. However, the red/gray line will hold no pressure at all. From what I've read this line goes to the vacuum reservoir. It seems on older models the vacuum reservoir was located in the passenger side front fender. I see nothing that looks like the examples of vac reservoirs on either fender. The red/gray line is only 6-8 inches long in the driver's side of the engine compartment and then it goes thru the firewall. Doesn't seem to make sense to me that the line would go thru the firewall then back out to get to the passenger side. Does anyone know where this reservoir is on an 83' 500sl euro? (probably the same as an 83' 380sl). My guess would be it must be under the dash on the drivers side as I've had the glove box out several times and not seen anything. Thought I'd ask before I have to become a contortionist to get under there and look.
Thanks
Marc

Never had to access it and don't know of anyone that has. Access has to be through the left side panel where the brake pedal and hood release are (LHD) I can show you where it is but that is not much help. Second picture is looking down through the hole in the first one.

Perfect! That was exactly what I was looking for.
Thank you

whats its purpose?