A/C Compressor

[SileNceR]

Hi,

The other night, the engine bay of my NB8B started emitting a strange rattling/clanking noise, which seems to mostly go away under load, and reminded me of the sound Air Con compressor clutches make on falcons/commodores when switching on.

I've pulled off the power steering/AC belt after ascertaining that this area is where the sound is coming from and i'm almost 100% sure that it is the A/C Compressor that is making the noise. Spinning the P/S pump pulley seems smooth and makes no noise, however spinning the A/C pulley makes (albeit slower) a noise very similar to what I was hearing with the engine running.

Is it likely that the A/C compressor will be servicable in this aspect or am I better off trying to find a replacement (new or second hand) compressor?

Also has anyone pulled the a/c compressor off as i'd rather do this myself to save some labour but would appreciate if anyone can recommend easiest way - I have a pit so can pull of the splash panel and work from the bottom, or am I better to pull p/s pump and work from the top?

[Mr Morlock]

Just go to an aircond service centre. Ask for advice- get a quote and if removing the unit is of use get that factored in.

[SileNceR]

Will do.

Mania can supply a new compressor for $250 so i'll take that into account also.

My brother is a refrigeration mechanic so getting it regassed if I replace it myself is no worries, he can get me new o-rings for it as well.

[SileNceR]

Decided to have a go myself, and since I couldn't find any info on it and can type fairly quickly I decided to do a DIY writeup for anyone else with what would appear to be bearing noise from their A/C compressor:



Removing Aircon – Mazda MX-5/Miata NB8B (2001-)

To remove the airconditioning compressor in the Mazda MX5 (NB8B model) is actually quite a simple task.

You can get the aircon gas emptied before you do this by a professional, this will save the environment however you may be advised not to drive without gas in the compressor as the gas contains fridge oil which lubricates the compressor and prevents damage.

You will need (maybe not all, but they all help make it easier!) –

• Large Phillips Head Screwdriver
• Small Phillips Head Screwdriver
• 12mm Spanner (Combination open/ring)
• 12mm Socket
• 10mm Socket
• Ratchet Handle
• 12mm Ratchet Spanner
• (Air ratchet would be excellent!)
• Medium flat-head screwdriver
• Jack/Stands
• Hammer & block of wood (maybe)

First, using the large screwdriver, undo the hose clamps holding the induction piping running from the airbox to the throttle body.

Remove the induction piping, unclip the PCV rubber hose from the U clip on the rocker cover and place on top of the engine out of the way, don’t bother unplugging PCV hose etc as it will not get in your way and just means more things to reconnect later.

Next, remove the power-steering/aircon belt. If you have done this before, this will be straight forward. I also suggest you check the condition of the belt at this time so you can replace it if need be. If you have not removed this before, you need to back off the 12mm bolt on the swivel mount at the front of the power steering pump. Then the pump needs to be rotated LHS (of car) down – I used a block of wood on the top line’s banjo bolt and a hammer to tap the pump down, rather than loosening and re-torquing the bracket, however suit yourself with this step. Remove the belt.

Remove airbox lid by unclipping, remove air filter and store on a clean surface. Remove 1 nut and 1 bolt holding airbox in place (12mm) and 1 10mm bolt holding pre-filter induction piping, lift airbox and piping away from car.

Remove bolts holding metal airbox locating bracket and lift away bracket, placing with airbox and airbox lid.

Unplug 1x red wire (single connector) which is attached to the loom for the Airflow Meter – this is the A/C clutch trigger (grounds via the motor, hence only one wire)

Sit Airbox lid out of the way (in front of the rocker cover worked for me)

Undo 2x 12mm bolts holding A/C lines to A/C compressor. You can move the power steering lines fairly easily for this as they are soft rubber and have a little extra length so are not a tight fit. If you had your gas professionally emptied, you will not have any gas released at this point. If not, be ready for a loud whoosh as the gas escapes into the air. I might suggest if taking this approach you work outdoors or in a well ventilated area – R134A which is used in these cars is not as harmful as older refrigerant gasses, but it’s still not oxygen so probably unwise to breath it in if you can help it.

Push the rearward line down below the compressor and out of the way.

Flex the frontward line and pull it up and sit it out of the way where the airbox bracket normally mounts. Be dilligent in collecting the O-ring from both of these, in my case the rearward hose’ o-ring fell onto the splash tray, and the front stayed in the compressor – I used a screwdriver to collect these. Place the bolts and o-rings together so you do not forget to reinstall the o-rings.

[SileNceR]

Those with smaller hands will be at an advantage here, but considering the limited space this isn’t as difficult a task as it seems. You can remove the four bolts holding the A/C compressor to the bracket in any order you see fit. In my case I left the hardest (bottom rear) till last however it would make more sense to start with the bottom bolts and do the top two last. You should be able to remove the bolts when undone, even the bottom ones as there is room to get them free. Do this as it will save you from dropping the bolts and having more trouble finding them. Note that you may be able to remove the bottom bolts through the lower radiator pipe access hole or by removing the splash pan – that’s up to you.

After removing the four bolts you can remove the compressor from the car. Unless you have have removed the splash pan or radiator for some other task, the best way to get the pump out is through the lower radiator hose access panel, which Mazda conveniently sized just large enough to fit the A/C compressor through with a little persuasion. Undo 1x small phillips head screw holding the panel shut and flex it down to remove the pump. If it grabs, rotate or apply a little force – the plastic of the splash tray has some give so this shouldn’t be a problem.


Removing bearing from A/C Compressor Pump

Extra Tools Required:

• 14mm socket
• Circlip Pliers (Medium?)

To remove the bearing from the pump, first remove the front clutch plate by placing it in a vice and removing the 14mm nut. Try not to place outer edges of the round plate in the vice as you could bend it. There are two flat faces adjacent to each other which you can place in the vice – no need to do it up too tight as the nut is not super-tight, you’re only stopping the clutch from rotating while you remove the nut.

The clutch will lift off, remove the clutch and place it and the nut aside on a clean work-area. There is also a washer under the clutch plate on the spline of the compressor shaft, remove this and place with clutch so you do not forget to reinstall.

Remove the circlip using the circlip pliers and lift the bearing assembly free.


That's all i've done so far, will complete when I have a set of circlip pliers (the last step is how easy i'm hoping this will be!)

[SileNceR]

Photos relating to the above:

Remove this piping as well as the airbox:


Airbox locater bracket


The power steering lines in the area you have to work on


How to place clutch in vice:


A/C Clutch, Removed


A/C compressor with clutch removed


A/C compressor front on showing bearings

[Okibi]

Can I edit this thread and place it in the tech archive?

[SileNceR]

Sure, I don't think there is much more to it. I haven't got circlip pliers yet so I haven't refitted mine but it's as per usual - installation is the reverse of removal.

[SileNceR]

N.b. Here's a link to a guide with a good exploded diagram also:
http://forums.audiworld.com/a6100/msgs/83988.phtml


Further to mine, it appears the electromagnet that operates the clutch is damaged on mine, not the bearing.

How it's supposed to sit:



The top section is not supposed to be freely removable, on mine it just lifted off:


Leaving behind the bottom section:


Note the wire also. There is another circlip to needs to be removed to remove the magnet assembly:


Then the compressor should look like such (note i've loosened the screw and removed the wire leading to the magnet assembly prior to taking this photo):


I've cleaned up and repaired the wire, now I just need to take it to an engine reconditioner or similar who can do very fine welding to repair the welds.

[Mr Morlock]

SileNceR - very nice write up- really useful and an effort that others can benefit from.

[SileNceR]

Thanks

I'll just add a note that the only reason i'm even considering getting this welded is that this part does not rotate with the compressor drive - if it did I would not bother, so if you have one that is broken on one of the rotating parts, not a good idea - it will likely be unbalanced and shake itself to bits!

[SileNceR]

I have had the electromagnet re-welded, and have re-assembled the compressor. Tests all ok giving it 12v, clutch operates as it should - very cool Problem is it looks like some sort of fuse somewhere in the MX5 is blown?

A/C fuse under the dash seems ok, A/C light in car turns on, but a 12v test light running on the A/C Clutch wire does not light up, and the A/C thermofan (i'm pretty certain, as per a lot of other cars, the second thermofan on the radiator turns on/off with the aircon compressor?) doesn't turn on.

I've looked at the fuses in the engine bay (on the driver side) and all look ok, I have only looked at the a/c fuse under the dash - does anyone know if any other fuse under the dash is used for the a/c clutch lockup?

[SileNceR]

Got it figured thanks to miata.net; the MX5 system (unlike aussie falcons and commodores) actually has a pressure switch which disables the aircon clutch from switching on if there is insufficient refrigerant gas in the system.

You have to vac with engine off, charge to around 30psi (on the LOW pipe!) then turn on engine and a/c, then a/c (and second thermofan) should engage and you can complete filling (should take around 14.2oz of gas according to miata.net) I don't know for sure as my a/c sticker was not replaced when my bonnet was replaced due to hitting a wallaby - can anyone confirm that 14.2oz is correct (or in grams either way) who has an NB8B with factory Mazda A/C fitted?