Need a lttle heater help please
 

Hi everyone.... Read forums daily, post once every ten years or so !
1980 911 SC Targa. Have owned twice for a total of 28 years.

Original heater blower in engine compartment finally gives it up. Waited a couple of years. Bought a used one on the forum. Worked ok for a year. Then gave it up. During my top end rebuild, flow bench the heads etc... While you are at it, i told mechanic to install new heater blower, which i had from PP. eache time old blowers worked, it would melt the hair off your legs. New blower....nothing. Not one drop of air. Pulled it out yesterday, bench tested. A moderate amount of air blowing, lots of motor whine. Very loud. Air flow but Nothing to brag about, though. While messin' around, i switched polarity with test wires. Holy cow... It blew my hat off literally. I determined that the way it was wired, motor and fan were running backwards. So i cleaned everything up and re installed today. Switched wires in my connector. Made sure flapper valves were working while i was at it. Then ... Almost nothing coming out in cabin. A small trickle. Way disappointed.
I know the heaters are anemic. But is this all i can expect ? Sure...with the engine running the engine fan will move a lot more air ... But did i just pay for a new fan that really does not do much of anything ? Or am i missing something ? Surely, the route the air hoses take cannot scavenge off all of the air flow ?
Your advice will be appreciated. Also, thanks guys. I read this forum at least daily. I still learn so much and get a good laugh once in awhile .....Joe

Hey Joe,

AC is anemic. Heater is the epitome of efficiency. Nasty-ass thing that will warm you in seconds - especially with the supplemental blower.

Something very basic is wrong. Your car is the same as my 81. Cables and such need to work properly in that can-of-worms pocket in front of the trunk "firewall". Find the air-flow bottleneck.

Bob,
Thanks for the reply...Man, I love reading your posts.

Ok...so i have always just pulled up on the red handles between the seats and heat comes out the foot well. I use dash board controls for defrost only. So what is in that"can of worms" pocket that i should check ? On your car.. Engine not running, turn on heater fan in engine compartment...do you get a decent amount of air flow or just a trickle ?
Thanks
Joe

Any chance a mouse has built a nest somewhere blocking the air flow?

That's just great - now Bob's head will swell to proportions rivaling his mamoth hamhocks!!! :D

Once you solve your "base" problem, flow restriction, this can improve flow ~30%

http://forums.pelicanparts.com/uploa...1413252683.jpg

And with this you don't get varying heat level with RPM rise and fall. Plus you're not "stealing" engine cooling airflow.

http://forums.pelicanparts.com/uploa...1413252766.jpg

If you have A/C the cabin heat blower rear be wired to provide addition condenser airflow at time most needed, slow stop and go rush hour traffic.

I had lots of problems with this system last year. In addition to a simply worn out motor,

The leads that feed the motor had a short In the loom. I replaced them back to the 16 (14?) pin connector.
The output and ground leads to my alternator were fried. I replaced them.
I replaced the voltage regulator. In hind sight, I think this was unnecessary.
I replaced one of the footwell blower motors with an AC condensor motor. Output was wimpy, not recommended, except for a mostly unused passenger side blower. I did save quite a few bucks vs a new assembly
Lastly,

I wired the motor backwards and couldn't figure out why I wasnt getting any airflow. I bet this is your problem.

Good luck,
Nathan

By the way, retrofitting a non Porsche blower motor is not worth the effort, imho.