Max A/C versus Normal A/C Question on a '73

[Steve's73]

Can anyone tell me what the difference is between MAX A/C and NORM A/C. My assumption is that when on MAX it should blow stronger. In my case all 3 blower speeds work fine but there is no difference between MAX and NORM. Any thoughts on where the problem could be? An switch or relay - I have checked the relay on the fender well - it's okay, checked the blower resistor in the Evaporator box - it's okay. Is this possibally a vacuum function???

Any information would be appreciated.

 

[69MyWay]

The difference is, that MAX recirculates the air in the car, while normal pulls it in from the outside and then cools it.

There is no difference in blower speed. However, in most cars MAX a/c sounds like the fan is kicking into higher gear only because the flapper door in the cowl is closing and giving you internal recirculation.

This will usually yield colder air as it keeps on cooling the air it already cooled. However, in a hot car on a hot summer day, putting it on max right away can actually take a little longer to cool the car down unless you open the windows and purge the sealed up hot air from the car.

 

[Steve's73]

Thanks, I thought everything checked out okay, I will verify the tempurature difference with the thermometer, any idea what the temp. difference could be?

 

[69MyWay]

The temp difference is all going to depend on the base temp of the recycled air going back into the blower.

I am sure there is a specific answer out there, but I don't know it, sorry.

 

[Steve's73]

I am more curious than any thing else. I am just happy to have A/C. I think I will reseal all the ducts for a little more effiency and air flow.

 

[vigman]

You can pick up efficency by doing the following

Chris is correct about Max VS Norm
It's just a re direct of where the intake of air comes from.


1) Remove the fan motor and give it a good lube.
2) While the motor is out, reach into the evap housingand pull out the 29 years of collected debris coating the fins there.
3)On the outside of the air box ( when everythings put back together) run the fan on max ( engine off ) and feel around where the pipes& blower resistor enter the air box. You can take some window caulking and get a better seal around these items.
4) Do you have a HEAVY DUTY fan ( 7 blade) & clutch? The more air you move through the condenser.. the lower the discharge temp of the air.

Just some thoughts.

Mike

 

[Corvettes White]

There is a door inside behind the passenger kick panel (that you can see if you look for it) that opens on MAX and another outside in the cowl plenum (that you can’t see unless you have hit a guardrail) that closes on MAX.

George

 

[Steve's73]

Thanks for all the help, got it straight now.