Learn me: A/C fan switch / electrical

[Driven97]

Originally Posted by kuehl

We tried one, it lasted less than 12 hours running continuously at 3/4 load.
If you buy a box full of them, you should be OK.

Fuuuu. Guess I'll just buy an OEM switch. Looks like the part has been updated.

[pavegeno]

Griff's variable fan speed controller has been working well for me for the last five years.

Griffiths supplies a range of air conditioning components for your Porsche 911,911s,911t,911 turbo, and 930, such as: Porsche air conditioning upgrades, Porsche air conditioning improvements and updates: Porsche barrier hoses and hose sets, Porsche c

It costs much more than $20. It is plug and play. It works, and works, and works, and works, and works, and works, and works...well, you get the picture.

[Driven97]

FWIW, it's in with a reasonable amount of fuss.

A PO had a large blue switch between the knobs that didn't do anything, but judging by a wire tap back there at one point it was to switch the AC circuit off and on. Seemed like a good idea, so I got a fresh switch and did the same. Now I can run the dash vents without AC at all if I choose. If the PWM holds up, I'll adapt the OE knob so that it'll look close to factory.

I ran it for about an hour yesterday, the PWM barely got warm. I have high hopes. Also of note: My fan at full blast was drawing only about 10A, the AC circuit alone was drawing about 4A.

Not bad for $25.

[Algernon]

Originally Posted by Driven97

Ok - thanks for the replies.
I'll at least fuse the front fan, and probably swap to a relay control. In the photo is a 7.5A, but the linked thread says 10A gives more headroom for startup - so 10A?

I'm confused - my front condenser fan run at about 3.7A, no-where near the 7.5A or 10A talked about here and other threads. Mine works, it runs happily without getting anything hot, but I imagine it's not very effective as a condenser! Any thoughts??

[Driven97]

Originally Posted by Algernon

I'm confused - my front condenser fan run at about 3.7A, no-where near the 7.5A or 10A talked about here and other threads. Mine works, it runs happily without getting anything hot, but I imagine it's not very effective as a condenser! Any thoughts??

I didn't check the run current for mine, but I'm going to go out on a limb and guess that the inrush current is much higher than the run current. A brushed motor at startup is basically shorted with only winding resistance until it starts turning.

tl;dr Basically it might reach 7A for the first split second then level off to 3.7A.

[Algernon]

Originally Posted by Driven97

I didn't check the run current for mine, but I'm going to go out on a limb and guess that the inrush current is much higher than the run current. A brushed motor at startup is basically shorted with only winding resistance until it starts turning.

tl;dr Basically it might reach 7A for the first split second then level off to 3.7A.

Yes, that's what I'm guessing, but the low run current was what surprised me.
I'm hoping for confirmation of the expected run current, and comparison with other blower motors run current, to see if it is worth replacing it.
Thanks.

[MConn]

I think the running current of the blower motor on mine was less than 5 amps, but I agree with Driven97 - the current of a starting motor can be 2 to 3 times the running current. I also used foam to seal around the front condenser to body, which would put more load on the motor.

Mike

[86 911 Targa]

^^^^^
As measured on our '86.