I think the decision is pretty straightforward.
Unless you have major system issues, then simple replacement of the 'faulty' parts will be cheaper than a retrofit.
If you are looking for the vintage air retrofit like Meccles did, then you will be spending a lot of time pulling the entire dash apart and fabricating.
It is not trivial. It offers some advantages and has some packaging disadvantages.
Bottom line?
You need a license to discharge and recover all automotive refrigerant gases in this country. (there are some "exploits" around legality of some alternatives, be aware of this.)
Not only that, if you have an R12 system, then the amount of R12 recovered has to be weighed and recorded. The R134a input into the system also has to be recorded.
R134a is the legally compliant approved refrigerant suitable for automotive applications in this country. Not bang gas or hychill or any other alternative refrigerant.
R12 can be recovered and recycled, but there is a "dodgy" way of getting around pulling the R12 and refilling with R134a that is known in the industry, and it involves "mixed gases". I'm not going to extrapolate on that.
The system has to be checked and found satisfactory (no leaks) before any refrigerant gas can be introduced. That's why fridgies have the need for certification and annual license renewal (money grab beancounters)
If your compressor has failed/siezed, then you will need professional assistance. Noone at home can perform a perform a system flush correctly, without extensive waste of solvents or doing damage to a system. Failing to flush a system after a compressor failure will result in a blockage at the TX valve or in the evap/condensor coil and render the system unstable and dangerous.
So here's a little bit of advice:
Find a licenced professional and leave them to do it properly.
By all means, if you wish to "improve" or "modify" the setup, do so, but also seek professional licensed refrigeration mechanic's advice.
Sizing a system requires a lot of calculation. It's a lesson in fluid dymaics, thermal conductivity and pressures/volumes as much as it is about "new parts".
Some basic issues:
schraeder valves are leaking - most common problem with leaking R12/134a systems. easy fix. low cost. Not always the problem, but often is.
Leaking hoses. often the hoses become permeable over time. most of these are easily replaceable, and in many cases the original metal manifold fittings or vehicle-specific fittings can be retained, and new crimp collars fitted. It's not always the case, but in many cases it is possible to 'repair' rather than 'replace' hoses which have a vehicle-specific fitting on the end of the hose.
Good examples of this are where the compressor has it's own vehicle-specific mounting location and the generic threaded port fittings on the compressor aren't accessible, so a different fitting with pad mount style manifold and "o-ring" are used. German cars are well noted for this as are some japanese cars.
Leaking evaporator core - if the evaporator is stuffed - replace with a new unit. The size and volume is very important here. If fabricating a custom evap, then there are many more modern and efficient units in generic sizes available off the shelf these days, but the gas volume needs to be adjusted for the differences.
If your blower fans stuffed, replace. Consider keeping and rebuilding the old ones - if they are salvageable. keep as spares. If you are going to do water crossings or sink your car into a boghole, you will want to keep these as spares... as experience would suggest.
Condensor - This is most likely the worst performing component in the vehicle, due to age and location - if it's the original. It will be corroded, it will have more bent fins or blocked areas than you would generally care to bother with. The RRC pusher fans are total crap and do nothing.
If the condensor is U/S (generally they are at this age, or they have a very short future on the end of a freshly overhauled system) then there are many newer and more efficient options available, and it would be wise to investigate this - for example, look at the D2a / p38 condensor style just as an indication. How you go about replacing a condensor will also involve how you intend to replace the blower fan(s) on the front. Generally speaking, the less shrouded the better the vehicles cooling system will perform, but also understand the relationship between engine cooling and HVAC operation - because these auxillary fans DO affect the vehicle operating temps when AC is on.
Your condensor fans need to be correctly sized with an appropriate degree of headroom (higher airflow than you need) to ensure that the vehicles engine can cool from an overheat situation.
That's not generally something people take into account, and neither did landrover when they decided to fit AC to the RRC. It's very much a 'slap-on' system with no decent engineered application.
The soft-dash models did get a far better designed system, but it cannot be easily replicated in cab without a complete dash swap.
So the impetus here, is that you can replace the condensor and two fans with a later condensor/fan setup or go for generic condensor or another model vehicle with the modern bar style and sub tank reservoir condensors(very efficient) and generic high flow pusher fans (single or twin speed, depending on requirements, or DIY a pwm fan solution - $$$) whether you want a single fan or two smaller ones - that's a fitment and fabrication issue.
regardless, get rid of those useless standard twin fans. they are the most ineffective pieces of junk on the planet - a real example of LR band-aid solutions.
That laves the little things - TX valve, Rec drier, pressure switches, and thermostat.
Pretty much all of these things should be replaced, period. Reason being is primarily age and efficiency, but also keep in mind that other than the thermostat, these are all parts of a sealed system, and choosing to not replace these will result in a short term before you have to go back, recover gas, replace al the bits you didn't replace and then vac down, regas.
All in all, there is not a lot of expense involved *IF* the major parts of the system are serviceable.
In my experience, the evap cores on RRC's are prone to leaking. So that's lower dash unit out and repair the leak or replace the core (nothing off the shelf for tube and fin core, try natrad) Ideally adapt a newer style unit from another vehicle- may need to change pipe fitting or routing - as well as a lot of cleaning and maintenance on blower fans and duct cleaning etc.
pulling the evap will mean also replacing TX valve, and the opportunity to replace thermostat is perfect.
So that's "job 1" to be aware of.
A regas after several years of inoperability means checking compressor, leaks etc.
It's pertinent to be aware of a couple things at this point.
1. you can do the minimum, or you can do an overhaul.
the minimum would be recover gas, vac test, replace receiver drier and pressure switches, schraeder valves, vac test and regas.
If vac test fails, then it's time for UV dye and function test. isolate leak(s) repair, vac test and regas if no leaks.
It's the second part that many try to skimp on... because "It's summer I need AC now!"
which is to say it'll probably fail halfway through summer on the hottest day of the year and you're going to regret not fixing it when you had the chance, because the grief you get from SWMBO will far exceed any repair bill...
When these things are working efficiently, they do cool the vehicle reasonably well in the front, but in the rear it's not "great". That is to say the ducting is pretty useless really.
When you consider the costs of a full overhaul with replacement parts (other than a failed compressor) versus wrath of SWMBO/kids or a retrofit, then the favourable option is to replace, rather than retrofit.
It really depends on how far you want to go.
Cooldrive and Ashdown ingram have all the generic replacement parts for condensor/evap/TXV/Rec-drier/thermostat/pressure sw. etc. and obviously compressors and hoses/fittings etc.
but without a fridge ticket, you still need a licensed professional to text and fill.
Hychill really is not an option here. It's what's known in the industry as a 'dry' gas, which means it has no lubricative properties. This is another reason compressors fail, but let's not go into the details of gas types or oil specifications and compatibility... it's a minefield, and there are corporations which control these parameters and the licensing authorities are very much aligned.
I haven't even begun to touch the electrical side of things.
You will need to check the blower resistor (replace with fabricated 3 speed resistors or adapt a PWM control) because the resistors are notorious for failing.
relay, pressure switch, thermoswitches etc all need to be checked and replaced as required (out of spec). ac clutch is another obvious one...
It's something that really deserves it's own thread.
So that's a HVAC overhaul 101 for you.
I'll post some images to parts if you want to see generally what is off the shelf.
recdrier2.jpgsandencompressorvbelt.jpgthermostat.jpgtxvalve.jpgrrc-condensor.jpg
I'll add more pics in another post.
Roads?.. Where we're going, we don't need roads...
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