Can I have everyone weigh in on whether they'd stick with R-12 or convert to 134a?

Voting time already!?

 

12 is completely out of the question other than for existing systems known to be in apple-pie order, or possibly where uber-originalism is desired...this isn't solely out of environmental concern, but for the simple practicality of current/future pricing/availability of 12...older systems simply need to be converted along with fixes, and this has been the case for years now...and it's really a myth that older systems won't cool as well with the new refrigerant- but you do have to make the basic efforts...a system of this age needs refurbishment...there may be one chance in a hundred that you could simply add some more 12 and have it come up working well- much better to plan for reliability and maintainability...

Your system has years of neglect and is likely nearly or completely discharged, which means you won't have to deal with finding a shop to recover the old refrigerant in order to comply with law...you don't by any means have to get every bit of the old oil out, but the more, the better- it's easy to use a squirt bottle of alcohol to load up the evap. and cond. and then flush through with air from each direction...although now that i'm thinking about it, with the TX still on there, it might be trickier with the evap...a new TX couldn't hurt, and may be more optimized for 134a...the compressor really just needs to be drained...new hoses could be considered, but may not be essential...

New drier is a must in any case and will also be 134-compatible...Charging w/o first vacuuming will not work because the air in the system will prevent cooling...

 

Yeah that makes sense. It does make sense to go ahead with 134a conversion as it's currently inoperable and that's a good starting point.

Where would the drier be located? I'm looking to putting the heater core and dash back together so I have a functioning truck.

I'm thinking it's in the engine bay next to the confessor but want to double-check before I start buttoning up stuff. anything on that box that I'd need to go back to? I see some hoses attached to it; should I crack open those hoses and check for O rings?

Also, I read that some members run a line of silicone sealant along the heater core pan where gaps are noticeable. Is this advisable or frowned upon as if fluid starts leaking it'd just be trapped in the box?

 

So I went ahead and dropped the box cause I should be thorough. I took the evaporator and removed its cover and rinsed it off. Is it OK to keep using? Should I be worried about the bent fins? Should I run a vaccuum on it to see if it's leaks?

I couldn't crack the nut loose on the connector so I loosened at the compressor and fed the tubing through the firewall.

I circled where I think the old thermostat tube used to rest but can't be certain. What's the routing to run the thermostat tubing to the evaporator?

Is the brass chamber the orafice or the expansion valve? I'm thinking expansion valve and don't find replacement parts for an orafice so I'm starting to think that wasn't around back then or at least not on the truck. I've realized the drier is the black tube on top of the condensor in front of the radiator.

Sorry for the noob questions, it's been awhile since I messed with AC.

 

I wouldn't worry about a few bent fins. You can check the core with vacuum just to be sure it doesn't leak. Be careful loosening the nut on the end of the hose,don't twist the tube.As for the thermostat control,use one like I listed in # 19. It has the correct wiring connections. If you look at the top of the evaporator case(right under the glovebox),there should be a small hole in it. That is where the thermostat tube goes. Yes, that brass thing is the expansion valve,there is no orifice tube. And since you have the unit out, replace both hoses.The connections at the evaporator ,and most likely the compressor,are flare fittings.I put a thin coat of leak-lock sealant on the tapered part of the fittings to prevent leaks.(R134 molecules are smaller than R-12 and will leak through flare fittings). All the parts you need are available from nostalgicac.com .They also have instruction guides with pics and diagrams of the installation of their systems, which are similar to ours.

 

What kind of fittings would I need to connect the compressor? They just have these tubes. Looking at the nostalgic AC website, nothing pops out at me and I'd rather just build what I can instead of buying an $80 kit.

 

there should be no reason the evap core should have any leakage unless you can see corrosion or damage....easy test is to dunk in water and put air press. on to look for bubbling....simply straighten any excessive fin bending as you would with a radiator....

with it out like that, you could look into whether a different expansion valve (TX) would work better w/134a....I've only done the conversion with newer orifice-valve systems....

the drier (or, drier-receiver) on newer systems is typically located at firewall next to the evap inlet, but on your system it's likely to be somewhere in-line with the smallest hose, coming from the outlet of the cond and going to the TX....it could be on the fender apron, or connected directly to the cond outlet....
taljust for reference, here's the refrig. cycle, starting from comp: the comp receives low-press warm gas from the evap, sends high-press temp-raised gas to cond, which cools the high-press/high-temp gas to precipitate and condense into a high-press neutral-temp liquid, which then goes through the drier to the TX (or orifice tube) which is a line restriction that only allows a controlled amount of the liquid into the evap, causing it to lose pressure and 'evaporate' from low-press liquid to low-press gas which absorbs heat (observed as 'cold', though scientifically there is no cold, just varying levels of heat)....this low-press gas which has absorbed heat and will now be neutral or warm is routed to comp inlet to repeat cycle....

the drier on newer systems is likely to be placed after the orifice tube, whereas on TX systems it's likely to be placed before the TX....

on an operating system, you should feel greatest heat on line coming out of comp/going into cond, then neutral heat on line out of cond, then least heat (cold) after the controlled restriction (at evap), then neutral heat once again going back into the comp- 4 stages....overcharged systems will not show as sharp a difference in temps and may send liquid into the comp, which is bad

 

Glad you mentioned this; I picked up an expansion valve from the parts store but looks different.

The unit that's on there has a capsule at the end of it's copper line where the new unit I picked up has a coiled pigtail. Would this still work or should I find something similar with a capsule?

 

I noticed today after running the engine for a bit that the top radiator hose appears swollen or is ballooning. I squeeze it and don't feel any relief.

I was thinking I should probably check out the thermostat or just replace it to be pro-active and maybe replace the hose.

After searching though, I'm unsure what the standard would be for a 1973 F100 302; I'm thinking 180 based off what I've been reading.

Any input?

 

normal for top hose to collapse when gripped cold and to rapidly become pressurized/warm and firm to grip as thermostat opens after engine is run for a few minutes...if hose is visibly expanding, replace it...thermostat sounds good, but if of unknown age it never hurts to replace...remember about possibly looking at the timing chain....

on the new TX, the coiled end serves exactly the same function as the bulb-end of the old one, to expose its internal gas charge to the varying heat of the expanding (gasifying) refrigerant, so that it can regulate how much to let through so that the system doesn't freeze up- just attach to line in same way...I see on the specs it says it's for either R12 or 134a- this sounds like it's just the old-spec R12 valve, which will generally work with 134, but is not optimum, as 134 has a greater net heat-absorption and thus less of it is desired to be going through the restriction, either the TX OR the orifice tube on newer applications...there are 134-optimized TX's as well as orifice tubes available online...

also, that black stuff holding the end of the tx sensor to the line and generally insulating things is called "mastic"; you'll want to pick some up