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post #1 of 5 (permalink) Old 08-23-2014, 06:55 PM Thread Starter
 
 
Join Date: Aug 2014
Location: Spring, Texas
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Not Cool!

Just found this site today and I'm glad to see a site that covers all years. I have a 1975 Impala Custom Coupe which is my daily driver. It has been a great car except for the A/C. Most common problem I have is with the A/C blower switch which I have replaced 3 times. Eventually only 1 speed will work which is low. It's very hot here in Texas and low is just not enough. I met with a guy who has a 74 Impala with the same problem. Anyone know the cause and/or fix?
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post #2 of 5 (permalink) Old 08-23-2014, 07:25 PM
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You have a relay that bumps the voltage to the blower up but only if the signal gets to it. There is also usually a problem with the A/C control switch which is spring loaded and vibrates with the car so that the points often burn out if not fully engaged. It is poorly designed at best and the whole thing could be better served with a less decorative and more functional switch, such as one with detents to hold the switch in place once set.

I won't even mention the quality of off shore parts bought at the corner discount auto parts store where the focus is on maintaining a low price by selling only low quality parts.

You will probably have to check each for continuity and resistance.

Big Dave
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post #3 of 5 (permalink) Old 08-24-2014, 05:52 PM
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one way around the problem would be to get a few relays and wire them up to the switch and fan circuits. The fan switch only deals with the load of the relay on/off (very small) and the relay handles the high load current to the fan. You can buy the relays to be rated well beyond the currents seen by the fan load.



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post #4 of 5 (permalink) Old 08-26-2014, 07:35 PM Thread Starter
 
 
Join Date: Aug 2014
Location: Spring, Texas
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Quote:
Originally Posted by dcairns View Post
one way around the problem would be to get a few relays and wire them up to the switch and fan circuits. The fan switch only deals with the load of the relay on/off (very small) and the relay handles the high load current to the fan. You can buy the relays to be rated well beyond the currents seen by the fan load.
Thanks. I am electrically challenged. How would I wire up the relays?
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post #5 of 5 (permalink) Old 08-26-2014, 07:41 PM Thread Starter
 
 
Join Date: Aug 2014
Location: Spring, Texas
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Quote:
Originally Posted by Big Dave View Post
You have a relay that bumps the voltage to the blower up but only if the signal gets to it. There is also usually a problem with the A/C control switch which is spring loaded and vibrates with the car so that the points often burn out if not fully engaged. It is poorly designed at best and the whole thing could be better served with a less decorative and more functional switch, such as one with detents to hold the switch in place once set.

I won't even mention the quality of off shore parts bought at the corner discount auto parts store where the focus is on maintaining a low price by selling only low quality parts.

You will probably have to check each for continuity and resistance.

Big Dave
Thanks. I've been using OEM replacement switches but they still burn out the points. Should I try to somehow insulate the switch so it doesn't vibrate?
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