1987 Rx7 with S5 Turbo II. I've always had some sort of AC problem with this car. I converted it to a r134 system and then realized two things: A: it didnt do jack sh*t in Florida and B: if you brought it up to r134 spec pressure the single bolt holding the lines down would burst out of the compressor and create a huge mess so I went back to the classic R12 system and it is WORKING! sorta.... BUT definitely better than the r134 conversion ever did!
It seems to pick and choose when it wants to work but there are some common factors:
Cold start in my garage
early in the morning
late at night
these are when it works perfectly fine even in the hot summer Florida heat, even when at operating temps. However If I come back to the car after its been sitting in the parking lot of my school, nothing, even after driving it for a few minutes, the AC barely works.
For reference, my car does not overheat, the hottest it gets is 94 and maybe 96C when im not looking and that's when I'm at max throttle on the freeway (I run a Microteach ECU and these are water temps from my laptop). I read a comment from a thread saying normal operating temps for a turbo is anywhere from 82-98C so I think im well within the clear. (but correct me if I'm wrong!)
So here is my question: what mods can I add to make my AC system more effective? Should I heat shield the AC line that goes past the exhaust side of the engine? what do I need to do? The FL summer heat is killing me but GOD I want to drive my car so much!

 

do you have a condenser fan? some FC's did, some didn't it depended on the model it started with. the relay and wiring are all there though

if you don't, find a fan to fit the condenser, and then wire a relay into the wire that goes to the compressor, so the fan runs when the compressor is on, it helps a bunch

 

What j9fd3s said is good advice if you don't have the fan. IIRC, the aux. E-fan only came with turbo or AT equipped FCs in series 4, and maybe all of them in series 5.

Another thing to consider since you said you switched from R12 to R134 and then back to R12 again - Did you replace the dryer with a new one during that last switch to R12? If not, it could explain why the system isn't working as well as it should. AC systems work like crap if ANY moisture is in the system with the refrigerant. Anytime you have the system opened up to the atmosphere like that to overhaul it and switch refrigerants, you really should replace the dryer with a new one. Reason is the desiccant inside a used dryer has already absorbed a bunch of moisture from the air & old system refrigerant, and won't be able to hold much/any more.

 

Thats a good point, I don't. But I think Ill need a larger alternator for that, right? the S4 alternator on my car is struggling as it is (I've been told the s4 alternators aren't that great -_-). I get I need to push air through the condenser, will that really make all the diffrence? also my rx7 is a GXL with a turbo swap so im not sure if someone just removed the fan when I bought the car or if it never came with it.

 

It works perfectly.... under the right conditions as i stated. but we did make sure the AC system was as close to stock as it was before we did the swap so I think I'm good on that one but correct me if I'm wrong. also we barely used the R134 system. It worked for all of about 5 minutes before blowing the bolt out of the AC compressor......

 

Did you blow up your compressor?

R12 and R134 are not compatible with the same oils. There's a massive AC thread on here for converting your R12 system over to R152 (air duster). Give it a good study. Switching over to the duster means using a modern PAG oil instead of mineral oil for R12. However, duster is significantly cheaper than an R12 fill up.

 

Kind figured someone was gonna ask this. No my AC compressor is working fine because the AC is working. If the compressor wassn't working, it wouldnt be blowing cold at all. the 2nd time the Bolt popped out of the compressor I replaced it with a new rebuilt compressor and put the r12 oil in before a friend helped me charge it. as for r152, not sure how much cheaper your talking about but i was able to get 6 cans of R12 off ebay for 80 bucks, and I only need to use 3.

 

Not saying it's your compressor but I had similar symptoms in my 2013 Altima. It's a/c compressor was on a slow decline until it popped. Maybe check the pressures on the a/c system when it's working and when is not.

 

you mean the Ac compressor exploded? Ok ill give it a check and come back when I do.

 

^Think about those conditions for a bit. The one thing they all have in common when it works is they are times when the interior of the car is at its coolest, requiring the AC system to do the least amount of work to shed the heat.

Yup, but I think you missed the point I was trying to make regarding replacing the dryer.... Your AC system was opened multiple times in hot & humid FL, and used different refrigerants. It's highly likely that if you're using the same dryer you had before that its desiccant is fully saturated and won't be able to absorb moisture any further. A saturated dryer will allow trapped moisture to escape back into the system when there's enough of a pressure differential across it. Even if you evacuated the system correctly and pulled a deep enough vacuum when you did so on the last go around, if you were using a used & saturated dryer, you're going to have problems. The AC might function OK under the easy conditions you're seeing, but add more heat loading and then the moisture that should stay trapped inside the dryer starts moving around the system and doing unwanted things - like freezing up in the expansion valve orifices, making it block correct flow of refrigerant thru the evaporator core.

You can get 4 cans of duster/R152 at Walmart or just about anywhere else for about $12, only need 2 cans to charge the FC A/C system. I ended up using R152 after my FC's compressor finally failed and I fully restored the system. Works great, as good as it was with R12, though I do seem to have a very slow leak somewhere that I had no luck finding with the dyes/UV light approach. If I evacuate & recharge at the beginning of the AC season, it will get me thru the summer here (MD), but I'll need to do that drill again in the spring when it starts getting hot again.

 

[pulls pants up] you kids and your damn alternators!

the automatic and turbo would have had the fan, but not the manual. car was setup to have that fan with that alternator, so it should be fine, although that kind of assumes the rest of the car is stock and working perfectly. there is a splice in the charging harness that goes bad, i think its where the battery power is branched, and if that is no good it acts like the alternator isn't big enough

 

thanks for the help! Ill look into a new dryer then. And is there anything I need to change to replace the refrigerant with R152?

 

Whats odd is this is the S5 Turbo II motor with the S4 alternator that it came with. So at the very least should I upgrade to an s5 alternator?

 

you certainly could. back in the day i had a t2, and everything was a little dim, so i did the S5 upgrade and it helped, but when i pulled it apart to do the 20B, i found that the charging harness was bad (there is a staple in it), and once i fixed that i found that even the S4 Alternator was fine.

 

There's a long thread on the R152 conversion here in the 2nd gen section, started by a guy who knows his stuff on AC - just search for "R152", it will be one of the first (and longest) threads that pops up. The key conversion points are changing out to a new dryer, drain/flush the old oil and switch to an Ester based lube, which is compatible with R12, R134 and R152 refrigerants. To give myself an instruction cheat sheet for when I did my AC restoration/conversion, I cut & pasted the useful tidbits from that long thread into a single document, and made some notes on how I did a few things differently - see attached PDF file for reference.

Since my compressor seized before I did the restoration & conversion to R152, I went all in OCD style and flushed every part that I reused (lines, hoses, condenser, evaporator core), and I replaced the dryer, expansion valve and every O-ring in the system with new O-rings, using the green HBNR rings which supposedly seal better with the R134 & R152 refrigerants. The green O-rings are also fine for R12. And obviously I got a rebuilt compressor for the job. My intention was to use the R152 first to see if the system would remain leak free and basically work OK enough to get thru the summer, and then evacuate & charge with R12 the next year. The R152 performed much better than I had expected, so after the 1st summer with R152 was done, I figured why bother switching back to R12.

 

Nicely done on the write up! Thank you