garrett376

Bill G has a great article on doing the heater motor bypass - thanks for the tips Bill!

Using his info, I ordered up the same specification of resistors: a 15W 50ohm 1% tolerance resistor to bypass the motor (the cool looking one with the yellow heat sink encasing it) and a 2W 18K ohm resistor to keep the NTC sensor from triggering the blower motor to activate when the engine air gets super hot.

It was quite a fun installation if you like soldering...

garrett376

I wanted to preserve all of the plugs in case I ever went back, so I disassembled the plug, then cut the wires for both the NTC and the blower motor plug.

garrett376

I used an aluminum plate (left over from my cut-off switch installation) to mount the heat-sinked resistor, and mount the other blower motor resistor/circuit breaker. The little 2W resistor is zip tied to the wire harness.

I mounted my little plate to one of the existing mounting studs that the blower motor used to attach to...

garrett376

And here's what gets removed - about 5 pounds of heavy-duty air blowing hardware! If I owned a scale, I'd weigh it... maybe I'll see if the neighbor has a scale

MA7008O

May by a sptudip question but, now, how do you preseerve the engine from it's air gets super hot?

bhensarl

Nice work, Garrett! Your installs just get cleaner and more professional every time. Now just powder coat that aluminum mounting plate black so it looks like it came from the factory that way. (Spraypaint would be easier, but you know how crazy we all are about powdercoating)
Brian

garrett376

Thanks Brian

I just drove it this morning and the heat works just as good as before when the engine is at speed. When stopped, it's a little less powerful than before, but the front blowers alone seem to keep hot air coming out even at a standstill.

MA7008O - That is a good question becaues Porsche obviously invested engineering dollars into designing the heater blower to activate if the air temps get high, by means of the NTC sensor. I don't think the engine will have any trouble, though, if this never activates - all previous engine iterations didn't have this feature. The rear heater blower only blows air over the header tubes - if that air is not blowing when the engine is off, I don't think it makes any difference. I think that if the rear engine underside cover were on, it might (but doubtful) help keep the engine from baking itself, but since my engine under tray is off on this car, the heat can just radiate out from below. Additionally, the rear blower does not always come on after driving when the car is standing still... So I don't think there will be any issue, either way - undertray or sans, functioning rear blower or not. But only those Porsche engineers really know the secret! If the Cup Cars can get away with it, then so can I!

JasonAndreas

The rear blower also sucks air from the top of the nearly sealed motor that would normally just sit there cooking everything?

garrett376

True as well (I never thought about that... but that is probably its primary function - thanks for the insight!), but I bet a lot of the intake air comes from the fan opening, too.

I still think the engine doesn't care if it sits there all toasty... watch me start pulling/breaking head studs like the hot running 74-77 911s!!!

Red rooster

I always thought that the fan was there to reglate the airflow through the heat exchangers .Motor idle -fan wins , Motor hi rpm - fan limits the flow.Not that it matters.Just out of interest why not put the NTC in the new pipe .The only "fan" being switched on is the 50ohm resistor?
Geoff

garrett376

Good point and that's an option if one wanted to drill the special slot for the NTC sensor, but with a low capacity battery, I'd rather just limit the NTC with a 32 cent resistor than let the resistor get toasty for no reason

You could also install the circuit breaker/resistor in the tube as well like it was in stock form... but again, grinding the new tube (which is fiber) didn't seem as easy as my little plate (which I already had)

garrett376

I decided a relocation of my plate was in order - I don't think moisture would cause trouble, but I didn't want to test it out. The original location would have probably gotten wet when I washed the car, or if it rained. So, thank goodness there is another mounting bolt from the blower motor, which is also further back, out of the reach of water

Jeff Curtis

garrett, where'd you find that gold resistor??

I've been searching with little luck so far, but figured you might have a link handy.

OK, I found 'em:

http://www.mouser.com/Search/Product...Gc3Bnpjw%3d%3d