I have a 71, and live in south Geo., so...I need A/C soon. I just got through redoing my A/C...new liquid line, drier, expansion valve, manifold hose assembly, vacuumed and recharged with R-134A. It blows cold air.
My question has to do with the volumn of air it blows. I have no other old vette's to compare mine with so, as a comparison, I'll use my 98 F-150 (or any modern vehicle). The F-150 A/C, set on max-air, and the fan speed on high, would be a 5 on a scale of 1 to 5, 5 being the highest volumn of air coming out of the vents. My vette, on the other hand, set on max A/C, with the fan speed on high is about a 2 or 3 on the same scale. Is that about right? or should it be blowing a higher volumn of air? If it should be, any ideas on what to work on?
Thanks. :confused:

 

The new GM replacement blower motor will push a lot more air than the old original one due to design. I replaced my 69 with a new delco and it made about 20% improvement. Mine is using R134a and blows nice and cold. I really can't complain... It is not quite as good as a new modern vehicle but hey it's 35 years old... :thumbs:

 

Thanks, blue. Will look into putting one on.

 

Also check your blower motor wiring and the relay mounted on the evap housing. Mine had some corrosion and the voltage at the motor was just 10V with the switch on high. Cleaning off the contacts increased it to over 12V and the blower was going noticably faster.

 

Thanks, zwede, I hadn't thought about the votage, but that makes a lot of sense...I'll check that out tomorrow.

 

Also make sure all your seams are sealed. You can lose a lot of air under the dash and not realize it. Make sure all the air doors in the box are open or closed as noted in the service manual (not stuck part way).

 

Mark...explain this to me: "Make sure all the air doors in the box are open or closed as noted in the service manual "

What box? :confused:

Thanks. :)

 

If you have a factory shop manual it explains where vacuum should be at each position on the control ****. You can verify that you have vacuum to the proper vacuum actuator on the A/C box under the dash. You can verify that the actuator is working and that none of the doors are stuck part way open or closed. The doors send air to defrost/floor/ducts and regulate how much air passes the evaporator and heater core. If the doors are not in proper position, air can go to where you don't need it.

 

Make sure there are no obstructions on the air inlet side of the evaporator. The pathway from the cowl has virtually nothing to stop leaves and debris from entering the evaporator compartment. When I took mine apart I found the evaporator to be 5/6 blocked off. That will shut down the cooling and the air flow.

 

Thanks, Mark, and NF....I'm making a list, and will check all these things this weekend...it is already 80 degrees here today! :smash:

Lots of good help on this forum.

 

It is a huge help to have a Digital Volt Meter, and take readings over the wiring....from engine ground to blower motor frame when on high...should see no more than .2 that's 2 tenths of a volt differance...anything higher and the wiring has failed.....I used a 8-10 ga wire from the blower frame connected to an el mondo connector under the screws to a bolt on my intake manifold.....that ground also included the windshield wiper and the high speed relay....on the a/c blower box just above the exhaust manifold where the wiring gets baked really well, .....

another thing is the overall voltage drop on the + side, going through the hi speed relay and so forth....gotta have about .4 volt drop MAX at the motor itself, as across the alternator output....meaning nearly no voltage drop....

the leaves in the pressure side of the blower are obvious....ME, I tied off and sealed shut the outside/inside air doors, removing the inside one.....so mine is in constant recirculation mode...doing 2 things....increasing airflow, and also cooling power....especially since the thing can't pick up any trash/leaves from outside anymore...to block the evap at the a/c coils...

OK, having said all that, there is a mod, greatly discussed last year...of using a C4 blower and motor assy.....available from Auto zone for about 40 bux or less....and making a 3/4 inch thick spacer, and mounting in position...this is good for about a 20% OR GREATER airlfow increase.....good mod...

of course I have been all through my system from A-Z and so know everything is ok...and modded and improved....finally getting with the C4 blower to the point the a/c will/can run ME outta the car on a 100f day with humidity 100% also.....now the thing is....

I gota convertible...which leaks so much air anyway...don't they ALL???....

that I do not miss having and outside air ingested into the a/c system..recirc as a permanent thing is not so bad....

top up or down....

GENE

 

Great help, Gene. Thanks. Will do all you suggest this weekend, except the C4 mod...that may be next weekend.
We have the 100degree/100humidity here all summer...I've been so hot before my ties have run all over my shirt! :lol:

 

bluevette...by 'new' GM replacement motor did you mean the one for a C4? or does GM make a replacement for the C3. The reason I ask is I haven't been able to find a Delco or GM replacement motor...I've found other brands...Factory Air, and Simmons, but not Delco or GM.
Any ideas would be appreciated.
Thanks