87 Reliant A/C Evaporator core

[mrfury68]

I need to replace the evap. core in my daughter's K ride. I've looked at a few sites & found 2 different styles & prices. The one was a "serpentine" style core for around $150.00. The other is a "normal" looking core for around $55.00. What is the "OE" style & why are there 2 types available. Of course I'm hoping for the cheaper of the two as I'm replacing the heater core also while I have the heater box out. Any info is appreciated. Thanks

[Pete in NH]

Hi,

If you mean an evaporator core with many U shaped tubes essentally connected in parallel by "normal core" that's the one I would use. The serpentine cores are theoretically less efficient in heat transfer because as the as the refrigerant leaves the expansion device at the input to the evaporator core it is at its coldest temperature. In a serpentine core as it picks up heat along its length the end of the core is working with warmer refrigerant. The parallel core with its many paths minimizes this effect. i'm a bit confused by your pricing as the extruded serpentine core is much less costly to manufacture and should be the less expensive core, in pricing i've seen this is the case. The serpentine core runs around $65 and the OEM style copper and brass parallel core around $125. Almost all evaporator and condenser cores are manufactured off shore today and quality can be an issue. Buy your core from someone you know will back you up warrenty wise if you have problems with it.

Also, if this A/C sytem has been converted over to the newer R134 refrigerant which is less efficient than the original R12 you may not get very good results with the less efficient serpintine core. By the way, the same parallel flow versus serpentine flow issue also applies to the condenser in front of the radiator. Which is why conversions to R134 are often disappointing preformance wise with the old serpentine flow condenser.

Hope this helps and let me know if i can help with any other A/C related questions. I posted some basic A/C systems information last year in this section it might be helpful to you.

[mrfury68]

Pete, thanks for the reply. The system was converted to 134 awhile ago. The condenser was replaced too with one from an Acclaim. It was smaller & lighter than the OE condenser but it mounted in with very little fabricating / modifying needed. I have read that for 134 to work well in an older system, a smaller condenser needs to be used. The A/C was working well until the evap went south. If I read your post correctly, I would be better off with the smaller evap. core. I'll look at your other posts too. Thanks again for your help.

[Pete in NH]

Hi,
Actually, for an R134 system to work as well as a R12 system a larger condenser is needed. R134 is not as efficient as R12 in transfering heat and needs more surface area in the condenser. That is why parallel flow condersers are often used. If you Acclaim conderser can out of an R134 car it is likely a more efficent condenser.

That is why i suggested the OEM style evaporator which is a parallel type design over the cheaper/ less efficient serpentine evaporator. The OEM evaporator has a number of parallel tubes connected between the input and output ports. The less expensive serpentine unit may work well enough , I don't have any experience with them. I've always stayed with the original design units. It's way too much work to dig it out of the heater/evapoartor case if you don't get the cooling you want.

[mrfury68]

Hi Pete, The condenser did come from a 134 equipped Acclaim. I also have a 68 Plymouth Fury III that I am keeping the R12 system. I looked at condensers made to replace the OE style in the older cars & thought they looked smaller, they were thinner. I never paid much attention to the way the coils ran though. Like the K car's OE condenser vs. the replacement from the Acclaim was thinner. Thanks again for your input. I'll keep you posted on how the job goes.

[mrfury68]

I finally did the evaporator core on my daughter's Reliant. While I was at it I also replaced the heater core, heater control valve & the heater hoses. As stated before, the system was already retro-fitted to 134 & had a condenser from an Acclaim that was 134. I vacuumed the system & it held around 26 inches of vacuum. When I recharged the A/C it got down to 42 degrees at idle on max A/C. Oh yeah, the day I charged it the temp was 88 degrees & really humid. Driving down the road the air is nice & cold. My daughter is very grateful & happy, she loves her K-car. Thanks for the input Pete.

[Pete in NH]

Hi,

Thanks for checking back in and letting us know things worked out great. 42 degrees vent temperature is quite good, especially for an R134 conversion. Enjoy the cool air for the summer!