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A/C tuneup


mikeringland

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Hey guys,

 

I wasn't sure which forum to post an A/C question, so I figured electrical was good enough for this one. I recently changed my A/C compressor and clutch and had a local shop vacuum out and recharge my system. It comes out cold, but the air flow seems weak, even on high speed. Granted, my daily driver is a '13 Tacoma in which the A/C is strong and ice cold, so it's hard to compare the two. The guy at the shop said my blower motor could be tired or my evaporator could be clogged with debris though too.

 

My plan is to inspect and most likely change the blower motor and maybe even the blower motor resistor. My belief is that these parts may be original. The original owner kept decent records of what he did and don't see these ever being replaced.

 

I would also like to clean the evaporator while I'm there. What's the best method to do that? Can I remove the black plastic evaporator case to get at the evaporator to clean it? Is there a certain cleaner to use to clean the evaporator? Can I accomplish all of this without having to empty out my refridgerant again?

 

I am a novice when it comes to air conditioning, so any advice would be greatly appreciated, thanks

 

Mike 

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I didn't order A/C for my 71 so I don't have it.

My first question is, do all 4 of the different speeds work? Do you hear the fan trying to go faster after each speed change.

I believe there is a special relay for the highest speed but I think if it was bad, when the highest speed is selected, the fan would just go off.

I believe there is a vacuum operated door that allows outside air into the plenum to be cooled or heated. If that door is not opening, there would be less air flow. Not sure of your year but the federal government mandated if there is a failure in a vehicle heat / A/C system, the air flow is diverted to the defroster.

That's all I can say, good luck.

Bruce

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I believe all 4 speeds work. I think it goes slightly faster as you increase the speed switch. It does work on high, so I believe the relay is good. I also believe that vacuum door is operating correctly. When I turn on the A.C. I can hear the door open and i can hear it close when I turn off the A.C.

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Can you change where the air comes out properly?

Perhaps one of the air hoses is off and all the air flow is going inside your dash area under the pad.

I don't believe the motor would be the problem. If it was not working correctly, it would not work at all or would start smoking or be noisy, IMO.

Big mouse nest blocking air flow????????

Good luck,

Bruce

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I can't answer all your questions Mike but, I recently had my factory A/C repaired by a local repair shop that included a upgraded POA Valve, Expansion Valve, High Speed Relay and Blower Motor.  

I don't have the knowledge to investigate how to determine if a blower motor is weak and not spinning needed RPM's or what those revolutions should be.  However, I did have my mechanic perform a RPM test on the blower motor and checked it against a 65 Chev with factory A/C and the 65 Chev's motor ran at a higher RPM.  Based on that, I replaced the blower motor in my 72 with the correct replacement for my application and the performance increase was very noticeable.  If competent, you can also measure current flowing from/to blower motor and High Speed Fan Relay and compare with factory specs if you can get them.  

The other option on fan velocity thru vents might be the material that seals around all those under dash outlets may be deteriorated to the point your A/C is escaping prematurely.

Bruce is correct.  If the door isn't opening for A/C, you will get that air thru the defrost vents in the dash pad instead of thru A/C vents.

PS - Just as a precaution, I replaced my High Speed Relay and the volume of air did not increase, so that was not the problem.

 

Wished I had a manual that spelled out all the performance specs as it would make it much easier to diagnose these issues. 

Best of Luck.................

 

Doug

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