a/c compressor to work on 24v

[dude8383]

bump, anyone ever get this issue 100% resolved?

bumping this up because i too would like to get the idle bumping.

[Good & Tight]

O.k finally got the a/c to work properly.

The DME deff needs the a/c signal to bump up the idle when switched on.

This how I did mine. 84 euro 318i M50TU e36 wiring harness.

Pull the a/c switch out from the dash leaving it plugged in.

Turn the ignition switch on (no need to start the car) leave the a/c button off.

With a voltmeter check the wires one at a time for voltage from the back of the a/c switch, the one with no voltage when off then 12 volts with the switch on is THE wire.
Mine was violet.

Now go to the DME harness and find the violet/gray wire, (I pulled mine right at the DME harness connection) that is pin #64.

You can verify with a MM that the wire does not have any voltage with the car on or off.

Splice a wire from the a/c switch wire that turns on and off to the violet/gray wire on the DME harness. and that's it.

You can verify that the idle bumps up 200rpm higher when turning the a/c on by doing this test.

Connect a MM that reads rpm to pin #1 on the diagnostic port.
Start the car turn the a/c on and remove one end of the sliced wire and the rpm should drop 200rpm, connect it back and it should raise back up.

Stay cool....

[kermugit]

I know that this is an old post, but I wanted to still keep this issue active. I have tried to hook up the voltage imput to pin 64, but it did not work for me. Checked the voltage form the a/c switch and everything ckecks out, but no change in idle. I feel that there is more to this issue than pluging in a input voltage. I know that the old DME had a seperate idle contol box (green). This regulated the idle with different voltage levels going into the idle control valve. So this sparked up a idea about running a fast idle set up kinda like a second ICV? I could regulate the voltage through ICV with a regulator and adjust to the find the right settings. This would be set up to energize when the a/c switch was activated.

[kermugit]

Okay, I have found the solution to the issue.... It is called a/c idle compensator kit! its for carbs, but I feel that this could be used to push open the butterfly just enough to raise the idle artificialy. I figure this is better than that heel toe dance shit I have to do on the street when a/c kicks on and off. I might be deploying soon. So, I will have to get starting on this bitch real quick like. If not I will get back to this when I get back in 18 mths.

[Supadave]

... Anybody got pics, i need pics

[Wishno87]

O.k finally got the a/c to work properly.

The DME deff needs the a/c signal to bump up the idle when switched on.

This how I did mine. 84 euro 318i M50TU e36 wiring harness.

Pull the a/c switch out from the dash leaving it plugged in.

Turn the ignition switch on (no need to start the car) leave the a/c button off.

With a voltmeter check the wires one at a time for voltage from the back of the a/c switch, the one with no voltage when off then 12 volts with the switch on is THE wire.
Mine was violet.

Now go to the DME harness and find the violet/gray wire, (I pulled mine right at the DME harness connection) that is pin #64.

You can verify with a MM that the wire does not have any voltage with the car on or off.

Splice a wire from the a/c switch wire that turns on and off to the violet/gray wire on the DME harness. and that's it.

You can verify that the idle bumps up 200rpm higher when turning the a/c on by doing this test.

Connect a MM that reads rpm to pin #1 on the diagnostic port.
Start the car turn the a/c on and remove one end of the sliced wire and the rpm should drop 200rpm, connect it back and it should raise back up.

Stay cool....

Has anyone else had success with this? Getting my install started right now and trying to compile all the information I need.

[Neil1138]

All,

Setup: 1989 325i. S52 OBD1 w/ red label 413 DME. '94 E36 325i vanos wiring harness (manual), DIY re-pinned/wired.

Swap thread: http://www.r3vlimited.com/board/showthread.php?t=305827

Like many of you, I have gotten the A/C working on my S52 swap. I had custom lines made: used the e30 318is line from the condenser > compressor, and fitted an S52 evaporator > compressor line to the stock e30 line using a #10-#12 straight fitting. Since my e30 has already been R134a converted, I merely replaced the drier, vacuumed the system and charged it up. The A/C blows cold and all is well, except... the idle when A/C is turned on.

My S52 idles perfectly without A/C on. But as soon as I kick on A/C, with the extra load of the compressor, the engine just doesn't know what to do. The idle hunts and hunts, fluctuating from 500-900 RPMs and almost stalling when stopped. I have referenced this other post for how to give the DME a signal to kick up the idle:

A/C Idle bump - Site R3vlimited

However, nothing has worked for me:

• I have tapped the black/violet wire off the back of the A/C switch into pin #64 (gray/violet) into the back of the DME. No effect on the idle.
• I have tapped the original M20 A/C signal wire (black/red) into pin #64 (gray/violet) into the back of the DME. No effect on the idle as well.

Both times, I have verified that the connections are solid. I'm getting +12V at pin #64 on the DME connector. However, this doesn't seem to be doing anything for me. Looks like others are/have been in the same boat as me. How did you guys solve the problem?

Does anyone have any thoughts on this? The hunting idle when A/C is on, is very annoying.

[MC Hammered]

Here is an update and a bunch of test results

Thanks for this detailed reply from pandaboo911 I was finally able to understand the missing piece of the puzzle. You need to ground the AC activation pin the same time you turn the compressor on so the DME does the idle bump.

http://www.r3vlimited.com/board/showpost.php?p=4610626&postcount=327

My DME is a MS41.1
AC activation input is black/grey and is pin 16
AC compressor turn on input is violet/grey and pin 19

Testing results:

1) +12v to pin 19, nothing connected to pin 16. This is where most of us are stuck. We get AC but when we get to a stoplight the idle hunts, rpms drops and we may get some shaking happening. So no idle bump.

2) nothing to pin 19, ground to pin 16. My standard idle is 850rpm, with pin 16 grounded the idle is around 930rpm. Remove the ground and the rpms drop to 850rpm. HOWEVER, if you permanetly ground pin 16 the car will always run at the higher rpm.

3) +12v to pin 19, ground to pin 16 applied and removed at the same time. Regular idle is 850rpm. When compressor is turned on (+12v on pin 16) and the DME is told AC is activated (ground on pin 19) the idle bump happens and the engine idles at 930rpm. When the AC is turned off (no power to pin 16, ground removed from pin 19) then the idle drops back down to 850rpm.

So while some people with different DME can luck out by permanently grounding the black/grey wire, I am not so lucky. So I need to put together a relay that will ground pin 16 when pin 19 gets +12v and my problems are solved!

[MC Hammered]

So I just got this reply from my tuner (their comments in red) and I wanted to share it to get your thoughts.

It's been a while since your reply to me. I had time to dig around in the car to do testing, fixed the CEL for the catalyst code, and only how I was able to get to the point where I can activate the AC idle bump.

I just wanted to clarify your statement here: "I did verify that the idle RPM for AC is set to 850 in the tune, as is the normal idle."
Idle=850. Idle with AC on=850.


So when the AC is activated is my idle rpm supposed to stay at 850rpm?
Yes

Or is it supposed to be bumped higher?
Stock idle is very low. So is stock idle w/AC, although slightly higher than normal idle. I raise both to a level higher than stock, but keep them the same value.

Here is are some test results to explain what is happening:

My DME is a MS41.1
AC activation input is black/grey and is pin 16
AC compressor turn on input is violet/grey and pin 19
You’re missing parts of your circuit, sir. I’m happy to help but we charge for items like this, as this has nothing to do with your tune and is entirely related to the wiring of your car. We charge $120/hr, so it may or may not be worth it for you.

It is the "You’re missing parts of your circuit" that got my attention.

I know that we are hacking the e36 system to work with the e30, but what other "parts" could we be using other than the pressure switch?

[janithdg]

AC Idle Bump

So I just got this reply from my tuner (their comments in red) and I wanted to share it to get your thoughts.



It is the "You’re missing parts of your circuit" that got my attention.

I know that we are hacking the e36 system to work with the e30, but what other "parts" could we be using other than the pressure switch?

from what i have read following is the way to do it, be separating the E30 Evap circuit to function on its own



Following is what i have come up with



can Anyone confirm this, or would this put too much strain on ecu by running two relays?

need to figure out a way to use the Pressure sensor with X20 Pin no 5 so the Pressure cut-off would work as expected

[MC Hammered]

Well this is the solution I came up with for my setup and have run it for a couple of weeks now. Depending on the mood of the car I may get a tiny RPM stumble when the compressor engages, but it is 90% better than before as you can tell by the videos below.

I am not sure why my compressor cycles on and off in short 7 second intervals, so I will have to get the system pressure checked when I get bored.

So here is the relay diagram to ground the "activate AC" wire, which is black/gray and pin 16 for my DME, when the AC on/off switch is activated





Took me a white to find the black/gray wire in the bundle. Used a Positap to help with the connection as all it does is pierce the wire jacket to make a connection.



Test wired up the relay to the ECU. Red clip is taking 12v from AC on/off switch which is also feeding the signal to the AC on/off wire, which is violet/gray and pin 19 for my DME. Green clip is connected to ground.

Testing in the garage was perfect, no RPM stumble when the compressor cycles on and off. As I stated earlier, how the car acts when the RPMs change while driving was a bit different.



NOTE: DO NOT try cutting anything when you have marginal lighting. I was debating if I wanted to just use the Positap vs. cutting a wire and directly connecting the relay output to the DME.

I needed to snip this one strand of black nylon webbing to open up the sleeve to wrapping the DME wire bundle. After I made the cut I realized it wasn't the webbing I snipped, it was the black/gray wire. Oh well... direct connection it will be!




This is how the idle was before the idle bump solution.

When the compressor is turned on by the switch, the RPM would drop a bit, when the compressor cycles off and on I get a very noticeable stumble which shakes the car.



This is how the idle was after the relay is installed.

The stumble I get now when the compressor cycles is livable, as it doesn't make people think my car is about to stall if I am stopped at a red light.

[janithdg]

idle bump

Thanks MC Hammered,
Idle bump is working now,
something little off the topic
i have a new issue where my tachometer/fuel consumption/temp gauges doesnt show reading properly,
temp gauge never goes above the blue zone, tach and fuel consumption has a mind of there own, i tried changing the instrument cluster, still same issue, i did check the batteries instrument cluster i had read each battery at 2.9v, and the cluster i changed to had 3v on each battery, im still using the m40 coding plug with the e36 m42 swap

any pointers on this
could it be an grounding issue or my ecu is toast because of my experimenting for idle bump?

[MC Hammered]

Can't help you with the cluster as I don't have any knowledge on how it is all wired.

[MC Hammered]

Update to my posted solution.

Short version: it works.

Long version: had my system vacuum tested and it passed, system was short 0.5lb of coolant, had it refilled and the short cycling went away and then it returned. I thought the issue was electrical in nature, but the shop decided to try swapping out the schrader valves as they are suspecting that is where the leak is. Since the system passes a leak test, the only place it can leak is the valves since they are depressed when the machine is attached.

Valves replaced, system evacuated and recharged, been running the AC for a few weeks now and the short cycling issue has not come back.

[E30m52b28]

Does anyone have what relay wiring diagram worked for this? Original pictures no longer available