AC Blower Motor speed changes with RPM??? - Team Camaro Tech
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post #1 of 10 (permalink) Old Aug 29th, 14, 08:11 AM Thread Starter
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Jeremy
 
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AC Blower Motor speed changes with RPM???

Hi All,

I have a Classic Auto Air setup in my 69 Camaro. It was a factory Air Car but someone ripped out most of the components and I figured it would be easier to go this route than rebuild the stock system, plus I wanted headers...

Anyway, as the title states the AC fan motor speed increases as the engine RPMs increase.

So I know that for radios when you get the engine whine this is usually due to a bad ground so I made the same assumption here. I added a ground wire straight off the negative terminal on the battery (I hope that's OK) but this has not fixed the problem.

I called Classic Auto Air and they told me that perhaps I needed a heavy duty Alternator :-( . This is a little annoying as I don't remember seeing any prerequisite of a heavy duty alternator when I purchased the system.

So before I go and order one can anyone suggest what I might try and weather or not a heavy duty alternator could be the answer?

thanks
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post #2 of 10 (permalink) Old Aug 29th, 14, 08:53 AM
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Steve
 
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Re: AC Blower Motor speed changes with RPM???

Check the tension on the belt that drives the alternator and if you still have the stock voltage regulator next to the radiator on the driver's side, try replacing that with a new solid state regulator.

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post #3 of 10 (permalink) Old Aug 31st, 14, 06:43 PM
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Re: AC Blower Motor speed changes with RPM???

Steve,
I have a Classic auto air AC system in my 67 and do not have the problem. I have a 100 amp Alt though. I would get a good volt meter and watch what the voltage does at the AC fan motor. I would then go directly to the battery with the same volt meter and see if it follows the voltage reading you got at the AC fan motor. If the wiring to your AC fan motor is large enough you should see no difference in the readings taken at both the battery and the AC fan motor.
If the readings are high at the battery and lower at the AC fan motor then it is in the wiring to the AC system. It could be too small wire size to the 20 amp fuse or wire size too small after the fuse going to the blower motor.
It sounds like your alternator / volt reg is working because it speeds up with engine RPM. Do your head lights do the same thing? Get a lot brighter with engine rpm. If so have your battery load tested at your local auto parts store.
You should see a good 12 volts at the fan motor with the engine not running and the AC on. After you start the car the voltage should be 13.5-14 volts or so.
I suspect something is wrong with the wiring to the AC system where the voltage drops to say 10 volts or so with the engine not running and the AC on.
Let us know what you find out.
When you have the problem try reducing load on your electricial system by having no other heavy load on.(electric fan,head lights, stero system,ect...)
Good luck
John

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post #4 of 10 (permalink) Old Sep 12th, 14, 11:03 AM Thread Starter
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Re: AC Blower Motor speed changes with RPM???

Hey Guys,

I haven't had much time to play with this issue but after talking to CAA directly they suggested that I try a new ground. So I made a new ground wire straight off the battery to the AC Unit so guarenteed good ground.

Same thing is still happening and now on high and sometime medium speed it is blowing fuses. I have tried 20AMP as suggested by CAA and also 25AMP which is what the fuse box indicates. Both blow. I could go to 30 but I really don't want to risk a fire.

Not sure what else to check.
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post #5 of 10 (permalink) Old Sep 12th, 14, 11:40 AM
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Re: AC Blower Motor speed changes with RPM???

Quote:
Originally Posted by jeremywrags View Post
Hey Guys,

I haven't had much time to play with this issue but after talking to CAA directly they suggested that I try a new ground. So I made a new ground wire straight off the battery to the AC Unit so guarenteed good ground.

Same thing is still happening and now on high and sometime medium speed it is blowing fuses. I have tried 20AMP as suggested by CAA and also 25AMP which is what the fuse box indicates. Both blow. I could go to 30 but I really don't want to risk a fire.

Not sure what else to check.
Go straight to the resistor block in the heater/AC control circuit under the dash. I would bet your problem is there! If any of the (3) resistors in the circuit are defective, the fan will not functioning properly and will blow fuses.

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post #6 of 10 (permalink) Old Sep 12th, 14, 06:00 PM Thread Starter
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Re: AC Blower Motor speed changes with RPM???

I don't even know what or where that is but I will check it out, thanks for the tip
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post #7 of 10 (permalink) Old Sep 13th, 14, 05:44 AM
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Re: AC Blower Motor speed changes with RPM???

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Originally Posted by jeremywrags View Post
I don't even know what or where that is but I will check it out, thanks for the tip
Follow the wiring harness to the dash heater box to find this mounted on top. Remove it, then check to see if anything looks melted or burnt and you can also check across the wiring connections with an ohmmeter for proper resistance readings. I don't recall the exact numbers, but, a "000" reading will indicate a short.


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post #8 of 10 (permalink) Old Sep 13th, 14, 09:23 AM
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Re: AC Blower Motor speed changes with RPM???

Karl,
If he has a classic auto air system this part would not be in his car. I beleive that was mounted on the stock heater box. Would that be correct?
Jeremy,
Try and run your system direct to the battery with a 20 amp fuse and see what the blower motor does. If that takes care of your problem at least you know it is in the wiring in the car and not the CAA system.
John

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post #9 of 10 (permalink) Old Sep 13th, 14, 09:50 AM
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Re: AC Blower Motor speed changes with RPM???

Quote:
Originally Posted by Hys67Camaro View Post
Karl,
If he has a classic auto air system this part would not be in his car. I beleive that was mounted on the stock heater box. Would that be correct?
Jeremy,
Try and run your system direct to the battery with a 20 amp fuse and see what the blower motor does. If that takes care of your problem at least you know it is in the wiring in the car and not the CAA system.
John
John,
I was assuming he had the upgrade kit which only contains the under-hood components. If the under-dash components were "ripped" out as well, then, you're correct! The OP said most of the components were missing, but didn't specify.

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post #10 of 10 (permalink) Old Sep 13th, 14, 07:26 PM Thread Starter
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Re: AC Blower Motor speed changes with RPM???

Hey Guys,

Yea when I upgraded I decided to go with a complete system from CAA as I wanted headers and the inside stuff was not in very good shape.

So yea no resistor block... I will try running it straight off the battery with a 20A, if that works I will probably just add a relay that is triggered by the original ac wire but power it through a fuse straight from the battery.

Someday when I save enough money I would like to drop in an LS(x) and at that point will probably rewire the car anyway so a relay will work until then.

thanks for the help guys. If a new wire does not work I will likely have to call the CAA guys and have them troubleshoot further.

thanks again, I love this site...
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