72 Coupe Blower Question W. A/c

[Edward J.]

Looking for someone that can tell me if the blower on the first setting can feel the air flow through the vents, ive looked at the blower its moving but at a slow speed the next 3 speeds you can few the air flow, thank Ed.

[Terry M.]

[Edward J.]

Re: 72 Coupe Blower Question W. A/c

Terry Good Idea, Thanks Ed

[Jim T.]

Re: 72 Coupe Blower Question W. A/c

Edward your A/C 72 should function like my 70. Anytime the thumb wheel selector wheel is turned to a function where the air conditioner compressor is activated and the blower/fan switch is all the way to the left, the fan will operate at a low speed automatically.
If you move the thumb wheel selector to any position that does not use the compressor and the blower/fan switch is all the way to the left the fan will not operate until you move the blower/fan switch to positons other than the left.

[Edward J.]

Re: 72 Coupe Blower Question W. A/c

Jim, the blower when low speed is selected the air flow cannot be felt the the vents or def., I can put the wiper door up and can peak in and see the blower motor cage moving but slowly, can you tell me if you cars the same as far as feeling air flow at the first setting ,maybe try the paper trick.the other 3 settings are perfect,I did as terry said with the paper system was on defrost and put the paper over the duct no paper movement.
I did use a volt meter and measured the voltage at the resistor at each setting low speed was about 3.5 volts, second was 6.5, third was 10.5 volts high speed the normal battery voltage 12.6( key on engine not running).

[Terry M.]

Re: 72 Coupe Blower Question W. A/c

Try the paper "trick" with the engine running. Sorry, I forgot to mention that is how I tested it on PV. The speed will be slower -- voltage lower -- with the engine not running. Battery voltage should get to 13 to 14 with engine (alternator) working. All the other voltages will be incrementally higher also.

One should also check windshield wiper operation ONLY with the engine running. Adjust the sweep with the engine off, and you will have to do it all over again when the engine fires up.

If the speed is still slow check the battery voltage with engine running. See if it gets to 14 or more volts. Your voltage regulator (inside the alternator) may be defective. Also you may have corrosion on some of the wiring connections. Checking and correcting that will be a slow painstaking process.

[Jack H.]

Re: 72 Coupe Blower Question W. A/c

Adding on to the above, the function of various controls is pretty clearly defined in the Chassis Service Manual, Section 14, Air Conditioning. You'll be somewhat surprised to find there are differences (quirks) between different cars in Chevy's lineup as to what does what specifically when it comes to heater/AC fan control. Also, there were minor differences in operation between '70, '71 and '72 cars in this area...

Next, the typical Corvette fan control switch doesn't have an OFF legend associated with its lowest position setting. That's because that position of the switch is NOT a fan off setting! It's actually the fan's 'lowest' speed setting.

As mentioned above, you have to rotate the Selector thumbwheel (A/C, Bi-Level, Vent, Htr, De-Ice) to its OFF position to actually kill power to the fan... It appears designers decided that IF the driver selected a climate function (any function), then he/she intended for the blower fan to run. So, checking/verifying fan function does have an aspect of 'cockpit' knowledge associated with it!

[John H.]

Re: 72 Coupe Blower Question W. A/c

It appears designers decided that IF the driver selected a climate function (any function), then he/she intended for the blower fan to run. So, checking/verifying fan function does have an aspect of 'cockpit' knowledge associated with it!

Jack -

I remember when that feature was added on most Chevy models - it was called "full-time low blower"; the legal guys got involved as a result of several carbon monoxide asphyxiation lawsuits (CO entry from the exhaust into the body through poorly-sealed joints), and the thought was that the full-time low blower would pressurize the cabin at all times, preventing CO entry.

[Dave S.]

Re: 72 Coupe Blower Question W. A/c

Jim, the blower when low speed is selected the air flow cannot be felt the the vents or def., I can put the wiper door up and can peak in and see the blower motor cage moving but slowly, can you tell me if you cars the same as far as feeling air flow at the first setting ,maybe try the paper trick.the other 3 settings are perfect,I did as terry said with the paper system was on defrost and put the paper over the duct no paper movement.
I did use a volt meter and measured the voltage at the resistor at each setting low speed was about 3.5 volts, second was 6.5, third was 10.5 volts high speed the normal battery voltage 12.6( key on engine not running).

I haven't had a chance to check my 71 A/C car but I went through this when I was PV'ing my non A/C 70 and 71 cars. Page 31 of the 68-72 Operations manual states "The blower should not operate with the left hand thumb wheel in the off position." What really happens is the blower does operate but no air blows due to damper being closed.
If I'm following this thread correctly that also seems to be the case w/ the A/C car.

[Pat M.]

Re: 72 Coupe Blower Question W. A/c

What really happens is the blower does operate but no air blows due to damper being closed.

That's exactly how my system operates on my non-AC 70 that passed PV.

[Terry M.]

Re: 72 Coupe Blower Question W. A/c

As I understand it Ed's issue is he believes the low blower speed is too slow, even in the "DE-ICE" mode. He hasn't said anything about the blower in the "OFF" position.

For purposes of updating the Operations & PV manual it will be handy to know how the w/C60 cars work in the "OFF" position, however.

[Jack H.]

Re: 72 Coupe Blower Question W. A/c

Interesting, John! I was kind of surprised when I first read the CSM (Chassis Service Manual) to find the number of discrete differences in blower fan operation across the Chevy lineup... It seems Camaro was almost always an exception to the 'rule' for whatever reason.

[Edward J.]

Re: 72 Coupe Blower Question W. A/c

I find it strange that the blower speed barely operates on low speed . The second speed does operate so the paper does move on de-ice, and seems to be properly blowing all other speeds, the blower resister seems to be working correctly but I think that if someone could check to see if there C60 works the same way that would help. if I had my guess I would say that if the car was in motion there may be air flow through the ducts, being the car has astro ventilation.whats do you think guys? by the way started car and ran no difference.

[Dave S.]

Re: 72 Coupe Blower Question W. A/c

I find it strange that the blower speed barely operates on low speed . The second speed does operate so the paper does move on de-ice, and seems to be properly blowing all other speeds, the blower resister seems to be working correctly but I think that if someone could check to see if there C60 works the same way that would help. if I had my guess I would say that if the car was in motion there may be air flow through the ducts, being the car has astro ventilation.whats do you think guys? by the way started car and ran no difference.

According to the 68-72 Oerations manual it says that for A/C equiped cars "the system is totally inoperative" when the left thumbwheel is in the off position. "If the control is moved to the MAX, NORM, or BI-LEVEL position, the compressor will operate, providing the ambient air is above 33-degreesF and the blower will automatically be on "low" speed."
Does that clarify anything.

[Edward J.]

Re: 72 Coupe Blower Question W. A/c

I hate to beat a dead horse,I took my car for a ride turned on the defroster mode and selected the lowest fan setting, now the airflow can be felt through the defrost duct while the cars in motion,this low setting on the fan puzzles me,.as I believe that its almost seems normal,Im getting the operations ready for next years reg. meet.
Theres no flow felt when car is sitting and running only when in motion. thanks for those of you have answered my questions. and would like to find someone with that 72 c60 car that can check there operation of the fan in the low setting. thanks Ed.