CIS Blower testing

75-911S · 10-06-2005, 08:10 AM

Being electrical circuit challenged, could someone tell me which wires to connect to the + and - sides of a battery to test the blower that sits next to the CIS air box if it is off the car? My blower wires are brown and yellow with black stripes.
Thanks.

Jack

safe · safe's Garage

Meassure in the contact with a tester.

I'll make a wild guess and say it´s toast

wilke3169 · 10-06-2005, 09:03 AM

http://www.pelicanparts.com/911/911_Parts/911_electrical_diagrams.htm

These diagrams will help. My suggestion as a fellow SC resident is to throw it away and backdate. Plenty of heat for our winter here.

safe · safe's Garage

Yeah, throw that crap away.
I made a T piece and connected the hoses to. I will get the proper parts later.

75-911S · 10-06-2005, 10:25 AM

Thanks for the link to the wiring diagrams. But they are Greek to me. I still need to know if the brown or the yellow wire is the "hot" one. If the blower is still good I don't want to damage it.

Jack

wilke3169 · 10-06-2005, 10:40 AM

I'm betting brown goes to negative terminal. I don't think it would hurt anything if connected backwards. Should be a path through either way according to the diagram, unless the motor is shorted to ground. I will check when I get home I do believe I have an old removed motor in the garage somewhere.

75-911S · 10-06-2005, 11:20 AM

Thanks Kevin. I appreciate your help.

Jack

safe · safe's Garage

It´s a dc motor it will just go the other way. brown is negative in the diagram from Haynes.

75-911S · 10-06-2005, 12:18 PM

Thanks guys. I gave it a shot of juice and it looks like Safe is right - it appears to be toast.

Jack

safe · safe's Garage

The blower motor is always on when the engine is on a 75.
In 76 porsche (they noticed that the blower didnt live very long...) added a switch so its only on when you have pulled up the heater levers.
Check out this site.
Heater system

75-911S · 10-07-2005, 05:24 AM

Great info Safe. Lots of other tech articles on that same site.

I guess I must have made it through last winter without the blower and didn't realize it. Now I have to decide if I want to try to find another one and add an off/on switch - or get the hoses and couplers to backdate to the pre-blower setup.

Jack

safe · safe's Garage

Glad I could be of help

The only difference between the blower and pre-blower setup is that the pre-blower don´t give you so much heat on lower rpms, you need to keep the engine above 3000 rpm.
But it looks way nicer without the hoses and you save a bit of weight where it counts

RoninLB · 10-07-2005, 06:40 AM

I back dated mine.

ianc · 10-07-2005, 03:25 PM

You'll need the blower if you spend time in traffic with the engine at low speed or near idle. If your motor is toast, forget about fixing it; I tried forever and gave up. New Porsche motors are extremely expensive, but you can adapt an inexpensive Grainger motor to work. See here:

The Wavey heater blower motor fix

ianc