I have an 86 base with an AC system that was converted to R410A, however the compressor is leaking and needs replaced. I don't know anything about A/C systems. Do I need a specific type of compressor or will OEM work? If so, what should I be looking for?

 

never actually heard of anyone running R410a in a car, R410a is a household air conditioner refrigerant used in fully sealed systems that have no seals or o-rings that can degrade so finding info about compatible seals is nonexistent for it.

R134a is easily obtainable and has seals and oils suitable for use in automotive applications, it only performs slightly less efficiently.

There is no specific compressor suitable for use with R410 for any car, closest you can come is one built to run R134a pressures since they are somewhat similar but R410 uses even higher static pressures than R134a because it can benefit from the ability to use that fully brazed/sealed hardline system. i have seen R410a systems run up to 300psi on the hotside, R134a only runs about half that pressure. if you're overcharging the system to suit the R410a it would explain why the seals are not holding, surprisingly if the compressor can even tolerate running those pressures, as none were designed to do it.

I'm not an expert in household air conditioning, i have however charged my system and know the pressures can be radically different between auto and home systems so i can easily see where this would cause some issues like this. you won't find many specialists who have experience in both home and auto systems either because though fundamentally similar they are equally different systems.

now the real question, how could someone even charge the system with R410a? specific gauge sets don't have adapters for automotive charge and evacuation ports.

 

Oh I got it backwards. It was converted to R134A, not R410A lol

 

ah ok, well most reconditioned or rebuilt air conditioner compressors now that fit the car already use seals compatible with R134a, i have used older R12 units on R134a and they worked just fine as well even though R12 has the lowest working pressures of all auto air conditioning refrigerants. most any compressor can handle the job, as long as it matches your line configurations as there was a few different manufacturers and line sets: Sanden and Nippondenso, there was at least 3 that i'm aware of(1 Nippondenso and 2 versions of Sanden compressors). a Sanden unit won't bolt to a Nippondenso mount bracket for example, nor will the lines fit. Nippondenso were generally S4 units and then they switched to Sandens on the S5 and later models(long as my memory is correct, its been many years now).

condensor units also tend to be suited for the type of refrigerant, all FCs used R12 and the condensors are made for it, however you can run R134a without a big loss to efficiency.

Basically just find the compressor that fits your application. There should be some markings on your compressor to indicate Sanden or Denso, the port configuration should also tell you which it is for and then you can match up a replacement with that info.

https://lh4.googleusercontent.com/pr...8Mrae55cDqmHGg

top one should be a Denso, bottom is a Sanden used on some later model S4 and most S5. The Denso are rather unmistakable with the large threaded fittings to connect the lines.

and a link for a little more info on compressors:

What a/c compressor do i have?? - RX7Club.com - Mazda RX7 Forum

Being you have an 86 it likely has a Nippondenso unit, which unfortunately are rather hard to source as they were only used for a couple years on the RX7 and reman companies never put much into keeping them on the shelves as recons. Most companies default to the Sanden unit for all years of FC3S, which is BS, because they won't fit. See the linked thread for info for retrofitting a newer compressor to an older S4 model though. The retrofit isn't completely straightforward, it requires a newer S5 mount bracket and adapter lines for the A/C suction and discharge lines.

This compressor visually looks like an 86-87 FC Denso but the application sais it does not fit, it is the closest i have seen to a replacement in a while though so i cannot guarantee it fits or even looks like the picture:


if it is a close fit for olders S4 cars, it might be worth looking into rather than dealing with making a Sanden fit an older model FC. It may require drilling and rethreading the a/c mount bracket, if the threaded holes aren't fit for an FC, however it may in fact be a mislabeled unit for our cars, since it apparently doesn't fit the toyotas which supposedly have vertical mount holes based on the reviews. in short it could be a hidden mine of Denso FC compressors. I almost feel like picking one up to verify it is this configuration, if so it's quite possibly a feasible replacement(i have a Denso unit car but i took out my A/C many years ago) but i wouldn't know for sure it would work for a while.

To me it seems like the aftermarkets were never even made aware that there was a Nippondenso unit for the early S4 FC, figuring out where they all went is the issue.

This ebay listing tends to reinforce my findings of this being the correct compressor, finally. 10P15C being the correct build for Nippondenso early S4 a/c compressors:

A/C Compressor-10p15c Compressor Assembly UAC CO 10437C | eBay

as you can see by their application list, it only shows 1991 compatability which is completely wrong, zero S5s that i recall ever had Nippondenso units. Sorry for being long winded response but the S4 Nippondenso unit disappearance has been a mystery for a long while that i never bothered to look into solving. being a 10P15C does not guarantee the mounting holes are correct, it just means the base compressor(so the images are correct) is the same one for our cars, so mileage may vary as to whether this is exactly our compressor.

 

i ordered one of the compressors and i have my mount bracket sitting on the shelf as well as my old original Nippondenso unit from 1987 there as well to test this all with. I doubt my compressor seals are good anymore so i figure i better test this theory before these all disappear. Plus at that price, why the F not? can't find anything for these cars new/rebuilt for a hundred bucks these days anymore.

 

I just checked, I have a Sanden. Previous owner must have converted it when he did the R134A conversion. Does anything need to be done before bolting on the new compressor? Never done anything with A/C systems before

 

The rest of the system O-rings should be updated to HNBR(light green) seals, there are kits for the retrofit. Most rebuilt compressors already use the new compatible seal compound for R134a.

 

It actually looks like rockauto has a rebuilt Sanden compatible with R134a, the rest of the system was already converted so I think that's all I should need (unless I am missing something)

 

then you should be fine. you will want to pull a vacuum on the system, especially if it has sat open to the atmosphere for more than even just a few hours. Pulling a vacuum on the system serves 2 purposes, it gets rid of moisture in the system which corrodes components from the inside of the system/reduces a/c efficiency and also removes the void of air in the system prior to charging it with refrigerant. a system full of air can mean roughly 20% of the system is air and it will not blow as cold with it there.

most people neglect evacuating the system and pulling a vacuum on it while doing major service work, and that is why they have premature failures and lackluster air conditioning function. even a basic vacuum pump that you can run off an air compressor will pull a vacuum of ~25"Hg. something like this:

Vacuum Pump - AC Vacuum Pump w/ R134A & R12 Connectors

or you can take the car to a auto service shop and have them pull it into a vacuum, or you can purchase an electric pump for ~$125 and get a better vacuum on the system. ~30"HG is ideal, the stronger the vacuum pump is the better.

read whether your new compressor is full or empty to determine how much oil you need to add to the system, generally i add about 2 ounces of PAG oil even for a prefilled compressor because there will be some oil loss no matter what. most instructions will tell you to empty the compressor and measure how much oil it has to determine how much to re-add to the system.

when pulling a vacuum let the system sit for 5 minutes and see if the vacuum level drops, indicating a leak in the system, there should be no drop in vacuum whatsoever after 5 minutes.

r134a requires less to charge the system as compared to R12, the FC should be just over 1lb (check the underhood label for capacity, they do vary a little depending on which of the 3 systems you have), most of the cans you can get at the store are 12ounces, technically 1 can should be enough, but just over 1 can would be ok. rule of thumb is to use 80% of the original R12 charge amount when converting to r134a, never more than 90%.

always get basic R134a, don't get that "super freeze", "super seal, leak sealer" or "full system service" crap, most refrigerants that have any additives at all do more harm than good, if they even work at all. for example leak sealant they add can destroy your evaporator and actually cause leaks instead of seal them.

 

https://jp3motorsports.com/blogs/new...-fc-rx7-ac-kit

 

HI everyone,
I just installed a new A/C compressor, I am surprised that the original part is still available!

This is what I have come across, the new connector on the compressor is too large to fit into the old connector on the harness!

It seems that my old connector has shrunk over 37 years.Go figure, anything to stop my restore!

So, I will have to sand down the new connector so that it fits.
I have selected two finger nail metal files to reduce the size of the new connector so that it fits.

Before I attach them, can I use my grease that conducts electricity into the connection?
It is a single spade connection, I will clean any grease on the outside of the connector.
I have been using this grease on all my ground connections.

Let me know what you think of my fix?