A/C 3 Speed Switch Problem?
 

Hey gang, I searched and couldn't come up with anything.

On my '85, the A/C blower intermittently changes speeds on it's own. Kind of creepy. The low speed works fine, the high speed works fine. The problem is with the middle speed. Occasionally (no pattern to speak of) when set to the middle speed, it will kick up to the high speed for a few seconds then back down to the middle then repeats. This seems to only happen when driving, not while idling.

Anyone experienced this? If it's just the switch, that's simple enough, but I don't want to go to the expense/trouble if it may be something else. I thought I'd ask first.

Thanks for your help!

Todd, I had such a problem once on my 84' Carrera, and it turned out the switch was shorting out internally. It is tricky to replace without damaging the console, as it is glued in at the factory(again, it was a long while ago, and I did the repair in a parking lot far from home in Charlotte, NC with pliers and a screwdriver.) That switch carries a heavy electrical load.

I would love to hear some more input on this. I believe this is what is going on with my car. My speed three will only work occasionally.

There was an article in Excellence about replacing the fan switch with an infinitely variable speed switch. IIRC it had decent instructions on how to remove the old switch.

I saw that. I sure don't like the price of that infinite switch.
I'll have to dig it out to see the step by step on pulling the switches.
Thanks for the reminder.

Look for a previous thread on this subject, titled "Carrera A/C fan switch -- an idea". If discusses an alternative to the expensive switch available from Griffiths.

Brian

Griffith's stuff is pricey but is quality and does work (no affiliation). I've been tempted to get the switch
I think you'll find the article in the 11/05 issue. Let us know what to look for/look out for when you do the replacement.

Tod,
Last summer, I installed a new evaporator fan motor because the old one was sqealing, indicating the shaft bearings were shot. When I got the new fan installed, the speeds changed just like you're describing. A few guys replied to my inquiries, explaining that the new fan motor exposes the next weakest link. The general opinion was that it was the resistor pack that is directly under the passenger floorboard. Basically, this is a 3-speed rehostat. A guy who stripped out his air condtioning for a track car sent me his for cheap. That did it....worked like a charm. There are probably plenty resistor packs available for cheap and it was only a 15 minute job.

Steve

Why is it that a variable speed 120V switch is cheap, but the 12V alternative is crazy expensive? There are plenty of auto/RV/marine applications that call for them -- is there a technical explanation?

Excellent question. I'd love to find a cheaper alternative.

There are 12V dimmers, for marine or low-voltage lighting apps. But my non-electric-guy's brain doesn't know if the amps required for a 12V fan would burn them out.

Here's one.
Here's another (the Skylark Low-Voltage slider).

Any EE types who can tell me if they would work with a blower like this?

How about something like this: http://www.midwestmotion.com/servoamp/25a12v.html

12 volts. 25 amp capacity. Remote-mountable potentiometer. $187. Price break of $151 at 10 units.

I have no pecuniary or other interest in this company...I just found the information with a Google search.

http://forums.pelicanparts.com/uploa...1190008695.jpg

FWIW - I do have the Kuehl variable speed fan control from Griffiths installed in my '89 and I have been satisfied with it In part I was attempting to reduce the noise associated with the AC since position 2 on the stock control wasn't fast enough and position 3 was too fast and too loud. The Kuehl product helped me accomplish this objective. I have no affiliation with Griffiths.

Regards,
David.

Do they sell the switch separately from the replacement motor?

Jack,

Are you asking re. the Kuehl variable fan control? If so - I purchased the fan control by itself.

Regards,
David.

What do they charge for it?

I think the fan control by itself is $300.

How about this one? 12 volts. 30 amps. $24.99 when it becomes available in a couple of weeks.

http://www.bakatronics.com/shop/item.asp?itemid=581

It looks promising. I wonder if it needs to be cooled by a fan?

I'm assuming you will be able to bypass the stock resister pack.