Hi guys. I'm trying to coax a 75 Monza 262 back to life. Its fairly complete and I'm hopping from system to system as I wait for my parts orders to come in.
The topic today factory air - which seems to be unique in the 75 model year as many things are. The system is physically complete. My car is a 262 V8, auto with Power steering and I presume factory installed air.
At first glance the system is telling me its close to working. On first check it was holding a couple of pounds of residual pressure of presumably R12, so I'm optimistic there wasn't a lot of moisture in the system, etc. I saved whatever gas that was and did a vacuum check on the system, but the system only holds about 10 pounds of vacuum. I'm hoping that the O rings and seals just got tired so the first step is to replace the schrader valves and all the O rings and see what I have. The compressor turns and the clutch pulls in when jumped - good signs. Things appear to be working in the air box, and the fan works on all speeds except full.
The valves went in last nite, they weren't a major source of the leak, O rings are next when the kit comes in. While the system is cracked open though its time to understand what else to deal with.
It appears that on the 75, the dryer uses a desiccant bag? I've never dealt with this before. Is it wise to wise crack this thing open and replace the desiccant bag? there has got to be a huge seal involved with opening the chamber up and I don't see that as available. Can anyone shed any light on what's going on here?
At the same time, I'm used to systems that use an accumulator style receiver/dryer. With an accumulator there is a pressurized bladder that provides constant pressure inside the vessel for the the orifice tube. If I'm just opening up a dryer to replace a desiccant bag, is there no accumulator function? I'm suspicious further because the orifice valve available for Monza online starts with the 76 model year, so I'm wondering if the configuration here is exotic, unsupported, or underwhelming?
At this point I'm generally happy with keeping the car fairly stock. I'm not going full resto-mod on this car, just don't have the funds or time - but if I'm going to enjoy the car in Los Angeles the air needs to work. Is my best path forward to try to bring it back to 1975 spec, or bring it forward to a 75/76 hybrid of some type?
Should I be trying to put in a 1975 style desiccant pack at all?, or is there a different receiver/dryer to go to? What's the full king in that case as I presume I'll need to switch over high pressure and low pressure switches etc.
And thoughts on the orifice valve? I know its going to be tied to above - but if I'm going to crack the system open it makes sense to put in a new orifice valve. The thing is - it doesn't seem to be available. It doesn't appear to be the same as the 76 valve which is readily available. Can I put in a generic VOV instead? Part number?
I'm thinking I'll probably continue to run R12, or eventually run R12. I have a small supply. I may run R12A for a while while I wait to see if the system is stable. My expectations are that even with the best of intentions the AC isn't going to blow me away in this car even running R12, and taking another 5-15% cooling hit converting to R134a would only make matters worse.
Any other tips on the refrigeration side of things appreciated.
As far as the fan not running on high, my manuals should finally arrive in a few days. My fuses look good, and I assume the resistor pack isn't an issue for full speed, so its probably the switch in the dash? Does full speed use a relay? Rock Auto does show a relay available but I assume that would operate all speeds?
If this does turn into a larger job, are there cross reference parts in general to other years or applications that have worked out well?
I've completely rebuilt auto AC systems before from air boxes to every other component and have the equipment to charge and monitor everything, I'm just looking at a 45 year information gap on the parts and options on what I can do with this stuff to get cold to come out.
As always - any help appreciated.
Tom