81 sc evaporator box ports

[cdaves]

Removed evaporator/motor. Bottom of box has 2 ports. 1 circulates cold air to the car interior. Was told the other(2) port (exit toward the driver side) pulls air from the tunnel--not sure about this. What purpose does the tunnel port serve and can you close it off?

[1982911SCTarga]

Porsche 911 air conditioning operates in a constantly recirculating mode. The "tunnel" port you're referring to is the outlet for cool air leaving the evaporator. The other one is the inlet that draws warm air back in from the cabin and then through the evaporator.

Brian

[cdaves]

thanks for the info-appreciate your time.

[Jim Sims]

"The "tunnel" port you're referring to is the outlet for cool air leaving the evaporator. The other one is the inlet that draws warm air back in from the cabin and then through the evaporator."

The above is incorrect for the factory evaporator housing; warm air is inducted into the evaporator housing through both the trapezoidal shaped opening located behind the passenger side floor board (under the forward part of the carpeting) and from the round opening into the center tunnel at the bottom driver's side of the "smuggler's box". Cooled air exhausts out the nozzle at the top left of the evaporator to a flexible hose and thence to the dash vents. There are sufficient openings into the tunnel that some warm air will return this route from the driver's floor wheel, etc. I'll try and post a photograph tonight.

[1982911SCTarga]

Thanks for the clarification, Jim.

Brian

[Jim Sims]

View of the smuggler's box showing the round tunnel nozzle. In cars without factory A/C, this nozzle is covered by a rubber cap. This image is from a non factory A/C car being prepared for A/C installation. The four holes in the "firewall" between the passenger foot well and the smuggler's box are the start of the trapezoidal warm air inlet hole.







Front, bottom view of evaporator housing; the round hole connecting to the tunnel nozzle is on the right. Note also the condensation drain line molded into the bottom of the housing; this is very commonly broken off by persons removing the evaporator housing that don't understand how the evaporator fits into the "smuggler's" box.








Side, rear bottom view of the evaporator housing. Note the trapezoidal warm air inlet with anti-rodent screen mesh. The round hole that connects to the tunnel nozzle can be seen on the bottom and some of the fan blower wheel vanes are visible through the cold air output nozzle. Also note the foam sealing gaskets which are important to avoid leakage of air (cold air out and warm air in) and resulting inefficiency. In many of the SC and older cars these gaskets are crumbling to dust.

[cdaves]

Jim,thx for info &pic--bought my MGB in Los Alamos.