Gunpilot

Found this little gem on Craigslist for $260.00! Complete car with a spun bearing.


Started to gut it and harvest the AC system


My LS car sure has a rats nest to deal with!


Here is engine bay before:


I'll post more as I deal with the wiring.........

Gunpilot

Its nice to have a car side by side to compare things to. I'm working on getting the harness all back on the same mounts and along the same path. New components dropped in nice after some wire redirection. Need to figure out best mounting for computer and fuses now. Looks like passenger foot well will be best option.

Gunpilot

Used factory Miata lines and cleaned up engine bay. Had to bend them around headers a bit.

Attached condenser to radiator. I hope those puller fans draw some serious air.


I was surprised to see that the GTO crank pulley uses the same 4 rib pulley that the Miata compressor uses. I tried to come up with a way to get it to work, but since it is on the opposite side of the motor, fittings were not working well. Gonna hook up a GTO compressor and find a shop that can finalize the connections for me.

Gunpilot

Just bought this little gem off e-bay. Plugs into the GTO LS2 ac compressor and turns the fittings 90 degrees and coverts them to standard AC threaded fittings. This should make fabricating lines to attach the Miata hard lines to the compressor easy (hopefully). Next steps: double check fitment of compressor and figure out electrical. I figure all I need is to connect power button on AC controller to the compressor? I believe in the 1996 model, the AC power was connected to the computer which in turn sent a signal to the compressor. All other controls are direct connected to the components (fan speed, temp control, and duct select).

charchri4

Loving this thread! I'd really like to get mine working too but can't get hoses made anywhere around here. Big surprise in a town of 1200 in the tundra.

On the wiring you have to put a relay in it because Mazda uses ground to close the AC relay and GM uses hot. So the button on the dash closes the relay using the ground side to switch it and sends B+ to the computer telling it you want AC. The other way you can do it is to tap into the signal from the little blue AC light in the dash and just jumper that off to the ECM. You have to take the controls apart a little but that's the way Shannon did his and it's still working. I used the relay method and but with no hoses have no idea if it works.

Side note a lot of swaps just bypass the computer and let it be manual control via the Mazda wiring that kicks on the fans and compressor.

So how would you feel about having your AC shop whip up a 2nd set of hoses that match yours and drop them in the mail to me?

Gunpilot

Unfortunately, compressor adapter won't be here till after weekend so I won't be able to get lines done then. I will do wiring though. Think I will direct wire button to compressor. Push button, send power to compressor. If I need a relay in there, I will ad it. If I figure out AC line issue, I'll let you know.

charchri4

You still have to have a relay in there because you don't want that little blue light circuit powering the compressor but Mazda already has one on the pass shock tower by the overflow bottle. It's in a bracket next to the 2nd fan relay.

The stock F body compressor manifold worked fine in mine but it is tight in there. LS2 could be different though.

No hurry for me they would not go in till next year anyway. I just thought if you wouldn't mind it would be a handy way to get them made and know they will work. Without driving to Omaha or Kansas City that is. I should have had Shannon do it when he did his but at the time it didn't dawn on me that custom AC lines would be as hard to get made here as snow plows are in Houston!

mazdaspeedmiata

holy cheap ....for a complete car too !!??
u can get your $$ back in like 1 hr

i am here for the AC, following

Gunpilot

Right! Keeping the donor around for a bit as I rob parts off of it to bring the LS car back to how it should be. I find I'm missing small brackets, fasteners, etc. This makes it real easy to make things right. PO changed out the 1996 dash with a 1990 dash to make it look clean with no airbag lines. Found he was missing a few fasteners. Not anymore! Should have wiring done this weekend and Ill let everyone know what my compressor connection plan ends up being and how it works out and cost of custom lines.

V8MiataMike

I think the advantage to having the engine computer in the mix is that it knows the A/C has been turned on and compensates for the additional load the compressor puts on the engine. When I cold start the engine for example with the A/C already on the EEC actually delays the clutch engagement a few seconds. It also turns off the A/C clutch at wide open throttle, etc. The EEC "manages" the clutch engagement based on the environment so to speak.

Gunpilot

I've been researching using the GTO LS2 PCM, but the pinout is confusing. I found on connector 3 pin 51 sends signal to compressor relay, but can not find out what connector and pin receives the signal from HVAC controls (push the blue button). Also, I will not be running high and low psi switches, so I need to figure out how to send those a signal to let the compressor turn on. More to follow when I get a few beers in me and study the papers all over the shop! LOL. It will all make sense.

Gunpilot

Ok, after a couple hours research, found out LS1 and LS2 PCMs are different. My LS2 gets AC request signal through a BCM, which I don't use in this swap. So I'm gonna use a relay to send signal direct to compressor from Miata HVAC controls. Done

charchri4

So that's why guys by pass the computer for it! Makes sense to me.

ToySnakePMC

I'm tuned into this thread as well. When I can find the time this Fall, I plan to take the same path as Gunpilot. LOVE the white NA purchase. You, sir, are certifiable Miata aholic now. Great buy.

MRM331

Once you have a length let me know. The fittings you'll have are not the same as a Ford compressor which means I could have a custom set of lines made for you. I'll have them done at cost so I can make up a kit for the LS using that adapter.

-Jason

Gunpilot

Jason- for sure. The adapter creates a 3/4-16 and 7/8-14 threaded nipple. Im hoping I can somehow use a mix of the few lines laying around to work, but most likely will need custom lines.

It's strange the LS1 PCM has an AC request signal in the wiring diagram, but LS2 does not. It was frustrating me until I came across an article about the LS2 BCM (body control module) that integrates with the PCM on a CAN bus. For AC, the signal from the car control goes to the BCM first, then to the PCMwhich sends out a compressor on signal. Without BCM, you can't trigger the compressor on signal. Only option is to use a relay to send 12v to compressor. From swaps I read about, a manual tranny car has no issues with change in engine load. Auto cars do have issues. Anyway, only way to know is DO IT!

MRM331

Originally I would just wire up the AC systems as "dumb" systems where I would just jump the wire that came from the HVAC controls to the original ECU to the wire that left the original ECU and ran to the rest of the AC system. I would then just swap out the Miata AC compressor plug with a Ford one and be done with it. On a 1990-93 car the stock Fan relay was tripped by the thermo switch or the AC system so they actually needed no further mods to work. On a 1994+ car I had to jump an additional wire at the old ECU plug to trip the AC fan relay.
While this caused a slight drop in RPMs it was not enough to stall the car and was not that big of a deal. If it did become a problem I planned to wire a canister purge valve into the compressor trigger wire and then plumb it to the manifold to create a controlled vacuum leak whenever the AC compressor cycled on. I experimented with this and found that a standard vacuum hose diameter leak was just enough to bump the idle just under 500 rpms.

I now include AC control in my harnesses that allow the A9L to detect compressor activity and bump the idle accordingly as well as shut the compressor off during WOT and cranking. I'm still running a system like described above since a MegaSquirt 2 does not have the outputs to wire in a AC shut off relay. When I build my MS3 harness and ECU I'll probably use an input and output to mimic the A9L function.

The point of my long-winded reply is that you should be able to trip the compressor completely independent of the GM ECU without to much of an idle drop. If you do get one then creating a controlled vacuum leak (I guess "dedicated Idle Air Bypass" sounds better) should take care of it.

-Jason

charchri4

Don't you have AC on yours Pat?

+1 on the NA buy! Gunpilot has knack for finding the deals out there!

charchri4

I have a feeling you could sell a bunch of these Jason. If there is an LS car close to you it wouldn't be hard to measure one up. I have a bunch of photos of Shannons lines somewhere and I'm sure he would be glad to measure or take photos whatever for us.

After hauling around a compressor that does nothing for 3 years and 18,000 miles I'm really excited about the possibility of having working AC! Thanks for posting this Rawn!

charchri4

A couple shots of Shannons

Gunpilot

Just picked up a LS2 compressor and was disappointed to find it was way too large for the space. Pulley was hitting the radiator hose and outlets were too close to frame to accept adapter I bought.




I did not want to rework the radiator mounting, so I went back to the Miata compressor. Using parts off the donor, I was able to do this:




Everything is not fully tightened down yet, but with some slight shimming I was able to mount up the Miata bracket and Miata compressor in line with the LS2 crank. There is no tensioner, so I will have to install the belt, and then the compressor to the bracket. Hopefully the LS motor does not over rev the Miata compressor! Im sure it will take a few trials in shimming to ensure the belt is straight, but looks good with naked eye. Best part is, I should be able to use Miata connections. Putting kids to bed now, and back in Garage I go.

charchri4

Wow didn't see that one coming. I wish I would have looked at that before I sold my Miata compressor! Red line on the 1.8 is higher than the LS so if the crank pulley is about the same size you should be fine.

Anyone want swap an LS1 compressor with 49,000 miles on it for an NA one?

Gunpilot

Lol. Well, it's on the opposite side of the motor and upside down in the LS, so there is still some fabrication ahead. I'll keep you posted.

charchri4

Ahhh you might not be able to run that puppy upside down. I'm not sure about radial ones but the old piston compressors had an oil reservoir in them and had to be reasonably level.

Gunpilot

Way to rain on my parade! lol. Did some research, and you appear to be correct. Max "clocking" recommended seems to be 90 degrees. It is recommended discharge line be on top. Back to the drawing board. Seems like I have 3 options now:

1. Find an AC compressor that will fit in that space with correct line placement
2. Move radiator forward so pulley clears hose
3. Switch to a Sanden compressor and bracket to move it up higher on the engine. This is assuming I would still have hood clearance.

I heard rumors that an early LS1 compressor has the AC line fittings coming out of the back instead of the side. I'll look into that today.

At least I got all the controls installed and the fans working as advertised. JUST NEED A COMPRESSOR THAT WORKS!!