I have a C-3 w/air conditiong. The system works fine and blows cold air. All vents, ducts and air doors work as per factory specs. I installed a new blower motor and checked that all speeds work correctly. Evaporartor coil is not blocked with debris. New blower motor was installed and is running up to speed. The interior of the car has been removed and space age insulation installed. A/C works good enough on an 80 degree day with no sun. As soon as the temps rise to the mid 80's to 90's on a sunny day I don't get enough air flow through the interior ducts. I understand that this a problem with the C-3's. Does anyone know of a cure for this problem? Thanks, John
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Re: 75 A/C
Hi John, One thing you might want to check is the water shut-off valve that is supposed to cut off the hot water to the heater core when you are in the high a/c mode. A easy way to do this is to wrap a rag around the heater hose (so it won't be damaged] and mash it close with a clamp, pliers,vice grips etc. If the temp. goes down and air is colder, the water temp valve is defected and needs to be replaced. Hope is helps. Page Campbell #2299 -
Re: 75 A/C
Another dos centavos. Cabin air flow is meant to work under two scenarios: (1) Max and (2) Recirc. Both involve the use of mechanical 'flip/flop' doors that are vac actuated. In both situations one door, say cabin intake, is open while the opposite, exterior/cowl inlet, is closed. If either is defective (bad vac line, bad vac motor, worn or stuck door), you can have outside (ambient) air mixing with make-up air (cooled) and loosing A/C efficiency (worse with forced convection effects of driving vs. standing).
The other 'centavo'. Are you sure compressor is working properly and R-12 at evap core is the temp it's supposed to be? Most modern A/C shops have infra-red 'spot' guns than can be aimed at a point for isolated temp readings....
Next, the Harrison 'box' hanging from the fire wall in the engine compartment has R-12 inlet/outlet lines feeding the evap core. They run through a cutout in the box's fiberglass that's SUPPOSED to be plugged with a foam stuffer to prevent underhood engine ambient from finding it's way into the mixer box. Sometimes these seals are 'bye bye' from time/rot and/or prior repair work. Since the seal was installed by Harrison into the original assy, it's not called out in the AIM and frequently overlooked.
Last, in '72 era, blower fan changed from metal squirrel cage to lighter/lower inertia nylon cage. Prior repair work may have replaced the fan motor as an assy (motor and squirrel cage) so you've accidentally got a high inertia fan blade there that's reducing your forced convection rate modestly.
On the few days, I've had the opportunity to run my '71 SB system under 80-90F ambient it was MORE than comfortable at both crusing as well as standing situations (doesn't get that hot that often 1/2 mile above Denver!). But, the 'bane' of this system is stop & go driving....
Since the hot water cutoff valve actuates (closes) with the engine running (vac source active), you will experience inefficiency. Run car, OK. Stop, vac bleeds off, engine temp rises, heater shut-off valve opens due to lack of vac, heater core heats due to water jacket conduction & convection. You return to car after a brief stop and it runs 'marginally' until you put on enough miles to close the heater core shut off valve and suck the residual heat out of the core that built up during engine shut down....Comment
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Re: 75 A/C
'75 A/C cars do not have hot water shut-off valves. Non-A/C cars have them, but not A/C cars.Comment
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Re: 75 A/C
HI Guys, Thanks for all of the info. I have gone over the entire system with a fine tooth comb. I didn't mention I have universal certification from the EPA in refrigeration. I have been researching a cure for this problem not only for myself but for all else to use when I find it( 2 years now). The problem isn't a lack of cold air (44 degrees at the duct outlet). It is lack of enough air(volume). I have even purchased some of the books out on this subject pertaining to the C-3. None offer better advise than the your advise. My hat is off to all of you. The books do specify that the C-3 flows about 160cfm and a typical GM vehicle flows about 300cfm. I have been told that the duct work is oversized for the vehicle and very restrictive with all the 90 degree bends invovled. All this adds up to low airflow. Anyone have any ideas from this standpoint? Thanks again, JohnComment
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