A/C - NA vs. NB

[Rogue]

Now where's that pic Meesh just posted.....

Aw come on Sammy, I'm just funning ya!

[sammm]

Aw come on Sammy, I'm just funning ya!

I noes it....I keep telling you to drink the NC Kool-Aid!

[brandonmpace]

The condenser on mine is beat to hell. After straightening a section of fins on it, it cools better. Too much work for that so I'll be replacing the whole thing soon and using synthetic a/c booster. No hardtop so I need everything I can get.
Shortly after, I hope to get a nice grille to protect it.

[Jiggerachi]

Have you thought about a difference in top material? I'm sure 20 year old equipment probably contributes more, but an old top may be also a part. I know in my car the AC used to really suck, getting a new top helped immensely, then I peeled the tinting off and i'm back where I started. I used to think the AC was going out until I stopped under a bridge and immediately was like, ahhh... I know my single layer canvas top still lets a lot of heat in, but it's not near as bad as the old ratty top it replaced.

Don't the later NBs have extra headliner material as well?

[Jiggerachi]

^+1 to what the other Brandon said . The condenser fins, if original have to be in awful shape for any car this low to the ground. I tried straightening mine out once, but gave up halfway.

[POS Racing]

Have you thought about a difference in top material? I'm sure 20 year old equipment probably contributes more, but an old top may be also a part. I know in my car the AC used to really suck, getting a new top helped immensely, then I peeled the tinting off and i'm back where I started. I used to think the AC was going out until I stopped under a bridge and immediately was like, ahhh... I know my single layer canvas top still lets a lot of heat in, but it's not near as bad as the old ratty top it replaced.

Don't the later NBs have extra headliner material as well?

Top on the '94 is actually newer than the one on the '02.

Top in the '02 is single layer with no window tint on the car. One thing that helps the '02 is the tan top and interior. But running same route with similar temps the '02 is cooling down faster then the '94. I need to get some vent temps to see what the difference is between the two.

[jrj512]

It might be easier just to make the '02 AC work like the '94 AC. Just tell the owner, NMC.

[POS Racing]

It might be easier just to make the '02 AC work like the '94 AC. Just tell the owner, NMC.

There is some question at the "Casa de POS" on who is the owner of the NB. All I know is I appear to be the owner of the '94.....

[OZMDD]

I wonder if Mazda used designed-for-134 compressors and such when they first made the switch, or if they just retrofitted existing hardware at the factory.

BTW - I keep having to turn off the recirc mode in my Triple Black NC since it gets too chilly if its under 105 outside!

[POS Racing]

FWIW, the AC in the NC is the cat's ass!

BTW - I keep having to turn off the recirc mode in my Triple Black NC since it gets too chilly if its under 105 outside!

The voices are getting louder! Get out of my head!!

[EricJ]

Easy to check the Freon in a R134a. Fixed my kids BMW, my wife's Toyota and topped off my Miata and checked the Blue Miata (94) before selling.
1. Go to Walmart, buy the reusable A/C gauge/hose ($15), buy a can of Freon w/ the leak sealer ($12?), a can of oil ($5) and a can of Freon without sealer ($9). (total=$41)
2. Put on some heavy gloves and goggles.
3. Fire the car up with A/C on max for 3 minutes.
4. Screw the can of oil on the gauge.
5. Plug in the hose to the low side. It only fits on the correct fitting.
6. Put in the can of oil.
7. Screw on the Freon w/ sealer and add until the pressure is between 25 and 45. When you are adding it, pull the trigger for 5-10 seconds, then let it run for 10-20 seconds.
8. Use the 2nd can of Freon if you need it. Don't go over 45.

The trip to Walmart is the longest part of the process.

[OZMDD]

I have an R134 pressure gauge/freon hose you are welcome to borrow. Let me know and I'll bring it Sunday.

[POS Racing]

Well I cleaned out the condenser best I could and it does appear to be cooling better.

I have one of these in the vent to get an idea of what the A/C is doing. Yesterday running down the freeway from TMS we getting 50 degress showing and it was cooling me and Evil KK down nicely!



Guess this week will put it to some real world testing.

[SirHustlerEsq]

Well I cleaned out the condenser best I could and it does appear to be cooling better.

I have one of these in the vent to get an idea of what the A/C is doing. Yesterday running down the freeway from TMS we getting 50 degress showing and it was cooling me and Evil KK down nicely!



Guess this week will put it to some real world testing.

After cleaning that condensor, clean the evaporator, then measure temperature again. 50*f is not acceptable, you should blow <=40*f on high with recirc, ~35-37*f on the lowest fan setting.

How low was the low side? If it's too low or been "garage-filled" a few times you have enough oxygen and nitrogen in the system that it will never cool properly. Never never ever ever use refrigerant with a sealant because it effectively lowers efficiency of the heat exchangers by coating them with sealant/insurlator, narrows the passages, and can't be removed (replace heat exchangers and hoses).

Consider getting a manifold from Harbor Freight for $50 to measure the high and low sides so you can check this:

I have a manifold if you want to come by and test it, I do hot have a vacuum pump yet.

There is really good news in all of this, Miata AC systems are awesome, the hardest part of servicing them is getting to the AC compressor. The evap/expansion valve can come out by removing only the dash (dash removal and steering column extraction on the Cherokee, must destroy the AC box to remove the evaperator) , there are only 2 o-rings in the system (GF's Jeep has 11), and you can get an expansion valve/evaperator for $75.

[Davidss]

A few psi of difference in pressure can make a bid difference in AC performance. Most service manuals or generic charts give you a pretty big spread, but with some intuition, and experimentation you can usually find the sweet spot. Talk to me in person at an event if you want more info.

Another thing that causes poor AC performance is leaky heater core valves. This is actually a very common problem. I always check this when doing AC work and find almost 10% of cars have issues. The easiest way to test this is to just use a vice clamp to pinch one of the hoses going to the heater core then go drive the car. If the AC suddenly starts working better you have a leaky heater core valve.

[Rogue]

too bad Miata's don't have them.......

[SirHustlerEsq]

too bad Miata's don't have them.......

We do have the old "flapper" twist mod to fully close the divider door.

[motorollow]

Gabkwong bought some cleaner that you spray on the condenser. He has not used it yet, so I am anxious to see if it helps. Also I saw some spray foam cleaner for the evaporator. It claimed to help get rid of the musty AC spell too.

[Rob®]

I always used a hose from behind (pointing toward the front of the car). Back-washed the radiator and condensor that way (would try to get between the two as much as possible too). You'd be shocked how much crap will come out.

[SirHustlerEsq]

I use old enema bottles.