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Pelican Technical Article:

911 Cooling Boost

Bob Tindel

Time:

30 minutes30 mins

Tab:

$0

Talent:

*

Tools:

Needle nose pliers

Applicable Models:

Porsche 911 (1984-89)

Parts Required:

Bend existing copper blower switch contact

Performance Gain:

Increase the cooling of your 911's engine

Complementary Modification:

Lift the rear lid
     Beginning with the 1984 Carrera, to provide additional engine cooling, Porsche added a complex control unit for the heater blower located in the engine bay. When the engine oil temperature is high, and the car is stopped, the control unit switches on the heater blower to get some extra cooling by blowing air through the heat exchangers. Because the heater valves are open, this hot air is simply vented into the atmosphere.

     If you have a 911 with manual heater controls and the heater blower in the engine bay, you can make an easy modification to obtain this additional engine cooling. Start by pulling up the rubber handbrake/heater control lever assembly boot, so you can access the blower switch, which is mounted on this assembly. (Figure 1) Using needle-nose pliers or a similar tool (a small hemostat works well), bend the tip of the copper switch contact (right side is easiest to access) toward the front of the car slightly. (Figure 2) Turn the ignition switch on, and operate the heater control lever to see at what point the blower activates. The objective is to have the blower come on when the heater control lever is raised only slightly (3-5mm), so that the blower is activated without moving the heater valve. If necessary, adjust the degree of bend in the contact. Put the boot back in place, and you are done.

     This small modification will allow you to switch the heater blower on manually when you are stuck in stopped traffic or need a little bit more engine cooling. Best of all, it is free!

Thumbnail
Figure 1

Using needle-nose pliers or a similar tool (a small hemostat works well), bend the tip of the copper switch contact (right side is easiest to access) toward the front of the car slightly.

Thumbnail
Figure 2

Turn the ignition switch on, and operate the heater control lever to see at what point the blower activates. The objective is to have the blower come on when the heater control lever is raised only slightly (3-5mm), so that the blower is activated without moving the heater valve. If necessary, adjust the degree of bend in the contact. Put the boot back in place, and you are done.

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Comments and Suggestions:
cary Comments: Just saw the article. I've used this for years. Primarily during July & August autocrosses. Between runs after car gets warm. Lift the rear lid and leave the blower on.
June 28, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
richkay Comments: how about using the air con to cool the air intake to boost power?
June 10, 2011
  Followup from the Pelican Staff: Not sure what your thinking. Like placing the evaporator in the intake ducting? - Nick at Pelican Parts  
Kenny the Carpenter Comments: This is all well and good for a 1984 carrera, but is there a control switch for a 1975 911s. The only switch in that location on my 1975 911s is the parking break on switch on the hand brake. Is there a relay in the engine bay and how do I id it? Is the engine bay blower controlled by the same switch on the dash as the fresh air fan? I'm rally getting confused at this point. Thanks for any help in this
May 5, 2009
  Followup from the Pelican Staff: I believe on the 1975 cars, the switch is actually built-into the handle. I know it was this way on the 914s... - Wayne at Pelican Parts  

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