Lotus Elise w/K24 swap AC wiring questions

K-Series Programmable ECU installation questions / support issues
DEEZEL
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Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

Mods, please disregard or delete the post above. I was making sure the image link would work.. now I can't edit it!

I don't have my ECU SN, version or cal as I'm not with the car right now, but I'll post it up tonight. I am running Kpro4.

Just about finished up with a K24 swap into a 2005 lotus elise. The last thing to get functioning is the air conditioning, and we're getting hung up on the wiring. We checked the compressor, line pressures etc and can get it to cycle on by jumping the compressor to the battery but we can't get the normal functionality (compressor to cycle on and off, cooling fan sequencing, activation with the dash switch etc) working.

I know there is an option in kpro to use the VTP sensor to bypass the normal "multiplexor" but I'd like to keep the stock lotus wiring and functionality in tact if possible. Searching some other threads here on this forum it sounds like this may be possible (see link below.) If not, we'll need help getting the VTP sensor option working..

http://www.hondata.com/forum/viewtopic. ... tus#p95569

Here are the lotus wiring schematics. Obviously all of the ecu connections have been removed, so we need to figure out how to make these connections to the Honda ECU (or elsewhere.) Each of these connections is color coded below:

line 370: blue
line 377: orange
line 362: red
line 364: green
line 363: pink

I have a friend who is much better at this than I am helping me out. He may post some more specific questions later. I know we weren't quite sure how the VTP sensor worked to cycle the AC if we need to go that route.

Any help is greatly appreciated! If there are any other schematics needed or questions that need to be answered let me know!

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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

Here is the switch pack module schematic (and edited AC schematic) just in case.. all of the wiring in the switch pack module is still in place.

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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

Here are the lotus ECU pinouts:

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Hondata
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Hondata »

With the Lotus the actual behavior of the switch pack module is not the same as what is shows in the diagram. In the diagram it shows relays but in reality it is solid state. The AC button is momentary and the switch pack handles the logic to toggle the AC state (up to but not including anything useful like remembering the AC switch between key cycles).
The ECU just wants a signal to switch on the AC compressor, so the bit in between you'll have to bypass the switch pack module and wire up yourself. On my Lotus I changed the momentary switch for a on-off switch (the same style are available online). My trinary switch and temperature switch were both non functional so essentially the AC switch was directly wired to the ECU input, but I would recommend the use of the trinary switch and temperature switch.
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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

Hondata wrote: Wed Apr 18, 2018 2:04 pm With the Lotus the actual behavior of the switch pack module is not the same as what is shows in the diagram. In the diagram it shows relays but in reality it is solid state. The AC button is momentary and the switch pack handles the logic to toggle the AC state (up to but not including anything useful like remembering the AC switch between key cycles).
The ECU just wants a signal to switch on the AC compressor, so the bit in between you'll have to bypass the switch pack module and wire up yourself. On my Lotus I changed the momentary switch for a on-off switch (the same style are available online). My trinary switch and temperature switch were both non functional so essentially the AC switch was directly wired to the ECU input, but I would recommend the use of the trinary switch and temperature switch.
Thanks for the reply. It sounds like that's pretty much the conclusion we'd come to also. We started to dig into the switch pack, but that sucker is buried into a place that isn't easy to access without surely breaking something (typical Lotus lol.)

Looks like we'll have some time to work on it some more tonight, so I'll post up some more specific questions about getting the VTP sensor to work for the compressor signal etc.

With the setup on your car, were you able to get the cooling fans to sequence properly? Or just run both of them when the AC is on? That seems to be one of our main problems.
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Hondata
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Hondata »

I removed the switch pack and have everything wired into normal relays (ECU, O2, starter, fuel). Only have one fan & different radiator too. The fan runs full speed when on, and does not run half speed like the stock application. ECU switches on fan when AC comes on. So things are much simpler with my vehicle.
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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

So we tested the wires coming from the Trinary switch and Lotus ECU 56 provides a ground once the A/C button on the dash is pushed. Our thought is we can wire this to pin B9 on the ECU to ground the VTP. This should also turn on both fans if they are wired to pin 7 on C101.

Now comes the weird part. With VTP as A/C input checked in Kpro we are seeing ACSW and FANC switch on which seems correct. But we are not seeing ACCL switch to on. It looks like pin E18 should be 12v with the AC off and 0V with the AC on. We tried multiple multiplexer settings (disabled, normal, and Lotus 2005) with no change as well as tried disabling VTEC oil pressure. Any ideas?
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Hondata
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Hondata »

Did you change the AC switch from momentary to on-off?
Are you using a PRB or PRA calibration / ECU?
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DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

We haven't changed the AC button yet, but we are thinking we may not need to as we may still be able to use the Lotus switch pack. I believe I have a PRB ECU (02 US RSX, with wideband 02) but I'll confirm.

We found out the ACCL output will only come on when the engine is running. Originally we were checking this with just the key/acc power on. There must be some ECU logic that controls this.I know the lotus ecu would check for AC line pressure and coolant temp before switching on the compressor. This also makes sense though when comparing some of my other vehicles, the ac compressor clutch won't engage if you just turn the key and don't start the vehicle. It will engage shortly after start up. I'm assuming this might make the vehicle more difficult to start if the clutch is engaged.

Thanks again for the help. I will update this thread when we figure out if we have to replace the AC button.
DEEZEL
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by DEEZEL »

Little update. We got the stock AC button and switch pack to work!

We just wired both of the stock cooling fans together, instead of worrying about the low/high phasing. I figure if it's hot enough to use the AC (which I use rarely) then it's hot enough to run both fans.

I'll post up a marked up schematic for anyone else looking to get this to work, hopefully this weekend.
MIK33B
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by MIK33B »

Hi all
I am going through this at the moment.
What was the end conclusion on how to wire the ac up using the original switch and switch pack?
Reezer22
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Reezer22 »

I am also dealing with similar issues and would love to know what you decided to do?

Thanks
Kr4nG
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Kr4nG »

Can someone explain the B9 function? From my understanding in kpro you will use that as the alternative A/C function. So does that mean you will supply 12 volts to pin B9 and then Pin E18 will output a signal. Will pin E18 give you a ground output or a 12V output?
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Spunkster
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Re: Lotus Elise w/K24 swap AC wiring questions

Post by Spunkster »

You can use B9 as the AC switch input and then E18 is used as the output for the AC clutch. It is just using the VTP input instead of an AC switch input as that is normally multiplexed on the RSX ECU.
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