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It just so happens I have a spare ECU off my 2001NB. I'm running an adaptronic now, so it won't be going back in anytime soon.

Give me a pm if you want to try it out or want to buy it.

Did the auto electrician check the AC system properly (compressor, fuse, pressure switch etc)? I only ask because if everything is working fine besides the AC and it is because the ECU, it just sounds very far fetched/unlikely. Considered getting a second or third opinion from other auto electricians?

Your best bet for a replacement ECU would be a Mazda wrecker or one of the forum sponsors (MX5 Mania, MX5/Automotive Plus etc). I'm sure you will be able to get one for around 5% the price that you got quoted for the new OEM unit.

Water in the passenger foot well could also be related to a blocked drain hose or faulty evaporator (behind the glove box).

Steps to take:

#1: Make certain it's the ECU that's the problem and not something more simple (as above, seems odd to only affect a/c)

#2: Trace the cause of the water and fix it (A/c drain hose, badly fitted windscreen, rust, etc)

#3: Replace the ECU after all that.



I'd still think it's not the ECU, computers are finicky things, it's rare that if they get wet only one thing stops.
I'd be looking at fuses etc first.

When you say the A/C won't run, what exactly do you mean? (button won't light?, compressor won't kick in?, simply not cold?)

When the A/c button is pressed do the engine revs rise slightly?

You can't simply swap ecus. Mazda's security system requires a matched ecu, key transponder and sender unit.

I'll attach a link when I get home for this (on the bus right now)

Mazda tech manual regarding the MIS (Mazda Immobiliser System):

http://www.mazdabg.com/ftp-uploads/MAZDA%20material%20for%20technician/CT-L1007_en.pdf

See page 01-2

ie. You'll need a matched ECU/PCM, transponder key and Immobiliser Module if you want to swap ECUs.

vilemartin wrote:The pcm of my NB series 2 (2001) has water damage. I'm told this is not unusual due to placement of computer in foot well.

Water damaged PCM/ ECU printed circuit board or the components mounted thereon in an MX5 NA or NB isn't quite as usual as you're being led to believe.

Yes, it can get wet under the carpet for various reasons, but the PCM/ ECU if mounted off the floor as it came from the factory usually only gets water damaged in flood damaged vehicles. That said, it can get wet around the wiring loom PCM/ ECU plug area which is at/ very near floor level. Perhaps check those connections before going to the trouble of having to replace PCM/ ECU, immobiliser & transponder key. Also, if you haven't already, have a look inside the PCM/ ECU to confirm water damage.

Ive had 6 inches of water in the floor of my car and dríven around with it splashing everywhere including obviously all over and inside the ecu before a few times and there has never been an issue.

Dann

I have ECU, key, immobilized box if you need.

Boyracer wrote:I have ECU, key, immobilized box if you need.

Hint: If you don't want to change all your locks and ignition switch over to match the new key, you can simply tape the new key near the coil antenna where you insert the key into the ignition - I believe the coil antenna is only a proximity antenna so it just needs to be close enough.

This will also effectively nullify any benefit of the MIS.

Could do a pnp ecu and a time for much less then the mazda ecu.

Must be some way to fool the ecu surely?

Sent from my GT-I9100 using Tapatalk 2

If there is minor corrosion on the ECU pins or an area on the circuit board, consider using a contact cleaner as well.