I have a 1987 244 that doesn't have working air conditioning. As far as I can tell it still takes r12 which is a problem. I'm also looking for parts cars to get a couple of trim pieces, etc, but I had a thought. If I could find a parts car that had been converted to r134a (or did any years have it from the factory?) then I could just take what I needed for a lot cheaper than getting it professionally done. What are some thoughts on this idea, what parts would need to be swapped, and is it even a viable idea to try and do?

 

The factory conversion kit included -

High side hose - new hose is double layer, r 134 molecules are smaller than r12, so leaks out slower
receiver/drier - r12 desiccant is not compatible with r-134
charging t fitting attached at the drier, on the high side
expansion valve - need to modulate r134 pressures
evaporator - original 240 evap had the outer pipes exposed, r134 evap is enclosed and sealed on the edges - since a 240 is a suck through design - air is pulled around the sides and not cooled
pag oil - drain mineral oil from the compressor since it does not mix chemically with r134
stickers to let people know the system has been converted

I've converted many, many 240 systems to 134 (years ago with the factory kit) - and even with the factory kit the system would blow about 5 degrees warmer than a r12 system. You could lower that a couple of degrees with a aftermarket electric fan in front of the condenser - but most of my customers that had that done were just satisfied, not happy, just satisfied.

And then since r134 pressures are higher than r12 - what's the condition of the x year old compressor, and the low side hose that gets fried by the exhaust manifold? Many times after completing a conversion - you charge the system and something else blows up - that's a hard one to explain - but it happened frequently.

Looking at parts cars - 01 -03 had the more modern system/evap/condensor - and used an accumulator/expansion tube instead of a expansion valve/receiver-drier. The 01-02 systems converted really well, the 03 was r134 from the factory. Be careful the r134 factory systems use different threads on all the fittings (you can't put a 02 hose on a 03)

 

are you suggesting looking at a 2001-03 for AC parts? and ideally i would find used parts that all still have life left in them but realistically i might need to buy a couple of new things.

 

No, and realistically don't expect the AC to work again.

Sorry I misspoke - the 1991-1993 cars not 01-03 cars.

91-92's convert easily and will blow cold. 1976-90 do not convert easily, a lot of stuff goes wrong during the process, and when completed after spending $$$$ still don't blow cold. So I don't recommend trying - unless you have PLENTY of extra money to spend on a frustrating project. You could take the entire system from a 91-92, but removal of major stuff would be required - to get the evaporator pipes out requires removal of the dash and part of the firewall. So this is not something you would do to a daily driver.

 

that’s too bad, thank you though

 

I would find out what is wrong with your present system. To me the most important part of the system is the evaporator. If that is in good condition all of the other parts can be replaced. I had converted my 89 740 years ago and through time have replaced everything but the evap. It blows at 38-40* with 134 so it had been sufficient for me. All was well until 2 weeks ago when I lost pressure. Being fall is setting in I'll take my time and find the problem and fix it. If it's the evap I'll have someone replace it but other then that I'll trouble shoot and replace the parts. Cost isn't a problem even though the car has 390K on it.

 

I agree - a 89 740 will convert well to r134 and easily blow 40 degrees. They use an accumulator and an expansion tube. The evaporator is a larger blow through design, and the evaporator tubes are completely enclosed. There is a blend door to keep the heat from the heater core completely out of the vent system. The system is plumbed with mostly aluminum pipes other than two short hoses. There is also an electric aux cooling fan in front of the radiator.

However a 93-95 940 that uses the same basic ac system as yours except is 134 from the factory - uses a larger more efficient condenser (and radiator) and uses a smaller pulley on the compressor so it turns faster to cool the 134 better at lower speeds.

A 87 240 uses an expansion valve and receiver drier. The evaporator is a suck through design (the fan is between the vents and the evap/heater core rather than before), and the evaporator tubes are open on the ends, so it only sucks through 85% of the available tube area. There is no blend door on a 240 - so any heat leakage from the heater core with it's prone to not shutting off all the way heater valve warms the cold air coming from the evaporator. A 240 also uses all hoses, that are more likely to leak and sometimes explode under the increased pressure from r134. A converted 76-89 240 will blow 45 degrees if perfect - that's after a few minutes on the expressway at 2500 rpms or so, fan speed 2 with recirculate on. It will blow 50-70 degrees driving on a hot day in stop and go traffic. A 87 240 does not have an electric aux fan in front of the radiator to help with stop and go traffic - you can add an aftermarket one and get a few degrees colder than 70.

 

i would assume i have r12 still (how can i tell?) also any suggestions on finding out what's wrong with my current system?

 

R12 has hookup valves similar to tire valves to attach gauges to, only on the back of the compressor originally. (they are not easy to get to, and there is a factory quick fill adapter near the drier that is NOT a 134 port) - R134 uses a different larger connection - if you have a r134 valve anywhere on the system, it's been converted to something. On a 240 you could find a r134 adapter valve most commonly on the low side of the compressor. The factory conversion valve is installed on the high side near the receiver drier replacing the factory fill valve. So, search for a 134 valve near the receiver, on the low side of the compressor, or some people splice them into the low side hose over the top of the engine. If there's not a funny looking charging valve anywhere it's still r12 - maybe. There have been other aftermarket solutions/refrigerants over the years that are no longer available.

To figure out what's wrong with your system - start with - is power going to one of the green wires at the low pressure switch on the drier? But - you already posted about the shredded wiring going to the low pressure switch on the drier - and seemed to not have an understanding about how that worked - So check the green wire near the compressor under the intake manifold. There is a delay relay, so you have to start the engine (the alternator has to be charging) and wait for ~10 seconds before the relay sends power to the green wire going to the compressor.
After that you will need at set of ac gauges - if you get far - the board can help.