Emerald + A/C unit

My car has been playing up and having the 5,500 stutter and thus I am think of binning the ECU and replacing it with an Emerald which although my be a little overkill should sort the problem.

However, does anyone know if the AC would still run and if not why not? I have spoken to Emerald and they have said that it would not work but I cannot not understand why this would be the case. (My A/C is not too good anyway as the plastic box at the front is cracked)

Many thanks


Easy answer it’s because the air-con is controlled by the Lotus ECU

Well the only reason I could think is that it’s powered by a switched earth to the ECU… But not having AirCon I would have no idea…

You could alway try getting your dealer to reprogram you ECU with the revised / recall map. This will cure the 5.5k stutter…

However if you get a misfire / wheel speed sensor goes foobar then it’ll limit you to 5.5k rpm tops

I am flippin useless with electrics, but I do know that the air-con is “linked” to the ECU. When the aircon is switched on, the ECU increases the revs at tickover.

Well most the Emerald ECU (therefore lotus ECU) connections are switched earths, i.e. the [insert sender / sensor / electrical gizmo here] has a live feed going to it all the time and the earth running to the ECU. When the ecu needs to activate the [gizmod] it will switch the earth on and thereby power up the [doohicky]…

The A/C solinoid “may” have a switched earth to the ECU… I’m sure you may be able to fudge it with an Emerald (there’s a fair few spare bits, mostly for turbo’s, boost control and what not) but there’s no “native” support…

Does that make sense???

If you want air-con to work as before but with an Emerald ECU then you will need to make your own control box to…

raise idle revs when its switched on.
monitor temp and switch on the half speed cooling fan but switching to full speed if required.
monitor temp and switch on the heat-soak pump after the engine is switched off.
disengage air-con if full throttle is applied for more than a few seconds.

Certainly not impossible, i designed a circuit for the heat-soak system but i ended up taking the pump off instead !!

Phil, in all honesty I think that is fairly impossible for me.

Blimey…I was always wondering why it is not working anymore since I left the island…
it’s flipping hot on the continent at the moment…over 30 celsius…

It’s much hotter than that in NY! Thankfully the A/c works well over here.


Alan Betts from http://www.abmotosport.com/ sells this a/c control unit for M3DK.