AC Idle bump

[RenaissanceMan]

Reviving a post from the dead! Any chance someone would be able to put up a picture of how they wired the relay?

I assume it ran as follows:
- Terminal 87 = Black/Gray A/C Pressure Switch (Needing Grounding)
- Terminal 86 = Violet/Gray A/C On (Needing 12V)
- Terminal 30 & 85 = Any Brown Ground Wire

Does this seem right?

Thanks,
John

Hey did you ever get this figured out? I can't find the pics either...

[jjc034]

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.

Reviving a post from the dead! Any chance someone would be able to put up a picture of how they wired the relay?

I assume it ran as follows:
- Terminal 87 = Black/Gray A/C Pressure Switch (Needing Grounding)
- Terminal 86 = Violet/Gray A/C On (Needing 12V)
- Terminal 30 & 85 = Any Brown Ground Wire

Does this seem right?

Thanks,
John

[E30m52b28]

I know it's a long shot but the pictures for the diagram are no longer available. Does anyone have the wiring diagram? Sent from my ONEPLUS A6013 using Tapatalk

[pazi88]

Why don't you just use the built in A/C compensation in ms41 (obdII)? There is A/C on pin in dme connector.

[MC Hammered]

Good to hear. Been keeping tabs on this thread as AC is one of my 'winter' projects this year.

Is your car OBDI or OBDII?

I am OBD2

[pandaboo911]

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.

Had the same problem here. Leak test showed nothing. Replaced shrader valves ($10) and its holding refridgerant. You can test if your valves are good by getting a cap (with an oring) and threading them on tightly with some grease. Run the AC for a couple days, If you hear a pop when you take off the cap, the valves are leaking.


Sent from my iPhone using Tapatalk

[b-rad]

I like this thread also, winter project maybe... my ac works for the most part, I would say 95%... if at idol and you turn on, works fine... it's like if I drive around and I let the RPM get to low, like from 3rd coasting to stop.

[BlackSpeed66]

Good to hear. Been keeping tabs on this thread as AC is one of my 'winter' projects this year.

Is your car OBDI or OBDII?

[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.

[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.

[Mwishlist]

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?

There is a Compressor Control Relay on the e36 cars, K19. It's on page 269 of my ETK (1998 e36). Maybe that is what they refer to as being missing? It looks like Abie199 basically recreated this relay for the E30.

From the ETK:
The pressure switch drives the grounding on Pin 16 of the ECU (Activate AC) through Pin 5 on the X20.
The Automatic Climate Control drives the +12v on Pin 19 of the ECU (AC ON Signal) through Pin 6 in the X20.
Then the K19 relay is driven by Pin 74 of the ECU (Activate ECU Compressor) through Pin 4 of the X20 (I think if I am reading this right?).

This troubleshooting post from Bavauto seems to confirm.

http://blog.bavauto.com/6932/bmw-e36-3-series-air-conditioning-compressor-inoperative-ac-not-turning-on/

Anyway, I think implementing the relay like Abi199 did by triggering it off the AC switch not the ECU is the final answer. Although I am not that great at relays. I'm getting ready to hook up my AC in the next few weeks so I will see if I need to figure this out.

[Mwishlist]

Nevermind, I just realized the answer.

[pandaboo911]

AC Idle bump

Wait so they said it didn't work? Why wouldn't they tell you what's missing lol

We need someone with stock idle to test this damnit

Sent from my iPhone using Tapatalk

[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?

[Sh3rpak!ng]

Nice work guys and perfect timing. I've got all the parts waiting for install.