Resolved 2G - A/C Control Unit ECU

[MarkAngelo05]

Hi..

My a/c was just working, I do not know why it stopped. Here are the symptoms,

-A/C turned on, idle raises, but compressor does not come on. The passenger side fan blips on and off the whole time, until I reach 210 then it comes on to cool the car down.
The drivers side fan never comes on now.

I tried to fill the a/c system up, but the LOW side port was just way too pressurized, so it would not let me insert any more freon, it pretty much kept most of the freon in the can.

I tried emptying the system to lower pressure, then used a new can of freon, slowly let it pressurize the system, but the a/c compressor does not kick in, nor the drivers side fan. I made sure the green A/C Light was on the whole time.

What could be the problem??? IT used to work, now I'm stuck!

Thanks!

Mark

IS the Driver's side fan supposed to come on even if the compressor clutch doesn't kick in while the GREEN LIGHT A/C Indicator is on??

Also, I'd really like to know if anybody else has experienced the passenger side fan blipping on and off.. fast small blips of power, and it moves slowly.. until the engine gets to around normal 210 degrees then it turns on.

Thanks!

Mark

------I "JUMPED" The a/c compressor clutch and got the compressor to 'kick in' BUT, the Drivers side fan still does not come on... My passenger side fan comes on when it reaches the appropriate temp to kick on....


What could be the problem??? IT used to work, now I'm stuck! Can it be the ECU? Doesn't the ECU control both fans and also controls the drivers side fan when the A/C is button is turned on and the green light is on? It also controls the a/c compressor clutch, correct???

Hi, I'm trying to diagnose my ac problem. Someone please tell me where the lowside a/c pressure switch is located. I cannot find any info in this stupid Chilton's manual.!

Thanks!

Mark Padilla

 

[rkmillerjr]

Yes, that would be great if you could find one. Let me know if and when you might be able to get a hold of the item!

 

[rkmillerjr]

The pull and save yard here has a few DSM's... if you want I can find you one next time im there (this week) and mail it... ill only charge for what ther junkyard charges plus shipping... im not makin any money--- anything to help a fellow DSMer

I sent you an email. Reply that you got it and I'll reply the .pdf as an attachment. Thanks for your help!

 

[fhudsonjr]

RK, you said your A/C was not working? What exactly was it not doing? Was A/C clutch not energizing e.g. you could not hear it click?

My A/C was not blowing cold air. The A/C switch on my 93 would work-light comes on when you push the button, but I could not hear the A/C compressor click. I trouble shot it as best as I could. I found I had 12v to the A/C relay contact that provides 12v to the clutch. I did not have any signal to the relay coil that would close the contacts. I am not sure if that comes from the ECU or the A/C ECU.

I found that if I induced 12v to the A/C clutch the clutch would energize. I held it there long enough to get some cool air coming out. Since I did not know why the A/C relay was not working I wired in a switch to the clutch and flip on the switch when I want cold air. An inconvenience for sure, but at least I get clod air( I also converted it ti r134.

I also have the problem of the car dying with the A/C clutch on and I put in the clutch. I have not figured that one out either.

Let us know if that ECU fixes your problem. I might see if aceofriches can scare one up for me, if I can't find one here.

 

[rkmillerjr]

Thanks for the info. I'll be back on the forum once I get the part for the repair.

 

[fhudsonjr]

RK, did you get it fixed? If so, what was it?

 

[rkmillerjr]

Your timing is good! I just got it working this week! I acquired an A/C ECU (A/C control unit) off of a fellow DSM Tuner forum participant who is from the mid-west and installed it. I seems to have solved my problem! It's great having this forum to make these type of contacts!
Dick

 

[Misterio]

I'm also looking for one of these control units, anybody know where I can get my hands on one? Or I can try to visit some junk yards, but i dont know what it looks like or where its located, can you all post a picture?

thanks

 

[rkmillerjr]

Here is what I got from the dealership to help locate mine. Let me know if the .pdf file came through OK. Feel free to email me if you don't get it!

 

[roni-wan]

MR227707 is that the part number?

 

[b00stedtalon2]

I removed all my A/C stuff a while ago. I have one laying around if I didn't throw it away already. I'll check tomorrow.

 

[rkmillerjr]

Yes, the part number is MR227707, but the Mits dealer indicated they are no longer available, so you need to salvage one.

 

[squeak104]

And as a reference there are two boxes down by the passenger kick panel, one gray one black. The one for the A/C is black.

 

[krummel21]

Can you get to all of these parts with out taking the dash apart?

 

[luizdiefenbach]

I have a 2G GST made on december/1994 and the AUTO COMP CONTROLLER is the MB946485, when I searched on jnztuning parts catalog shows that MB946485 was superceeded by the MR227707 $62.88 (Hvac - Controls - Blower motor - Control module
Control module, eclipse, 2.0l, w/turbo 1995)

Heres some pictures of the controller:

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My board has few main components:
IC1 and IC2: NJM2904 Dual Op Amp http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=5938
TR2, TR3, TR5: 603 41E transitors?
TR4: A1244 transistors?
E (near IC2): N14 13Z voltage regulator?

The rest are diodes, resistors and some capacitors

I will desolder the ICs to test them, and try to find what are the 603 41E, A1244, and N14 13Z parts.

 

[project95gsx]

Bump for the most useful air conditioning thread on the net. ever. thanks to gary and the wiring diagram i found, i was able to fix my a/c. my problem was the compressor wouldn't kick on - i could jump the contacts side of the relay and it would, and i got cold a/c in the car & my sight glass was swirling with liquid. i followed gary's steps and troubleshot all the way to the dual pressure switch (which was closed- like it's supposed to be), but from there it goes to the a/c refrigerant temperature switch which i couldn't find. i located a service manual & found the switch to be on top of the a/c compressor. the connector had popped off of the switch. so for anyone else who's a/c isn't working... here's some pictures.

here's the a/c refrigerant temp switch. i moved the connector out of the way for pictures, when i found it, it was resting on the 2 poles of the compressor, looking connected.

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here's what my a/c control module looked like. i checked it to ensure there were no burned chips or traces. mine was attached to the bottom of the blower assembly, near the door on the passenger side foot well. no need to drop the glove box like some people have said.

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P.S. while i was jumping the a/c comp relay, i checked the charge on the system and it was right at 45 pounds, where it's supposed to be. Also, when you aren't running the compressor, the pressures equalize on the high and low side. so get your low pressure gauge off the port before the gauge/refill pops.

 

[idt512]

My AC stopped working and ive verified that the AC control unit is not supplying the + output that its supposed to when the AC switch is on. Im having problems locating a replacement (both new or used), so my question is.. Is it ok to temporarily rig a + through a switch and feed it into the pressure switch? It sure would be nice to have AC until I locate the part.

My other question is... what conditions must be met for the control unit to send out a +, im wondering if its depending on another input 1st in order to provide the +?

 

[96eclipzGsT]

Have you checked to make sure you are not low on freon? The pressure switch is made to cut out the a/c when pressure gets too high at a stop light or too low while driving. If it is constantly running you are going to put major stress on the compressor with the high psi and could blow seals out of it or blow a line off.

 

[idt512]

Yes I know how the pressure switch works and it is not my problem, Ive got no output from the AC control module. If I rig my own + through a switch and hook it up to the pressure switch, then the pressure switch and the regrigerant temp switch will still be part of the circuit, im not planning on bypassing those switches. I just want to know if its safe to do so. And im trying to get in-depth info on the ACCU itself and what its functions are in finer detail.

 

[96eclipzGsT]

Do you have a pic of what you are talking about then? Where is it located?

 

[Spades]

So has anyone dissected the AC control unit yet? is it just the transistor that fails? if so does anyone know what type of transistor it is and where to purchase it?

 

[97gst_spyder]

I need to replace the ACCU on my car. Can I just cut the yellow wires and re-solder them to the replacement ACCU?

 

[red_devil]

Quick question about a/c. Since that the 12V goes in series to the dual pressure switch then the driver's side fan relay and then to the A/C refrig temp switch. If the pressure switch sees nothing it will not trigger the fan or the ECU to up the rpm? I replaced my compressor and tried filling it just to see if the clutch would engage and im getting nothing, no fans no change in rpm and no clutch engagement. I probably should get the system evacuated and charged but I wanted to do it with a dyi can for now.

 

[Enraged78]

I've also been wrestling with the MB946485 controller for a few days now. I hope this helps someone else out. After pouring over the wiring diagrams for the controller for a while and playing with a multimeter for a few hours, we now know the following:

1. MB946485 is a controller for DSM air conditioners that were manufactured with the two-step econ/regular button. I don't believe DSM's with the one step use this controller, as they use the newer type controller instead. (If anyone has ever seen otherwise let me know). The MB946485 has two inputs (blue, and blue/black wire), one for economy A/C, and one for regular. One wire is set to +12v for economy mode, and both are +12 for normal mode.

2. The adjustable dial on the MB946485 seems to control the temperature differential between regular and economy modes. (Based on my limited understanding of reading circuits) See: 2g Eclipse Tech Info Manual Pages 7-36 and 7-38

3. MB946485 has TWO temperature sensor inputs, one for air temperature, and one for fin temperature. The fin temperature test from the shop manual works, but I cannot find one for the air temperature sensor. They do output separate readings, and are quite a bit off. The tech manual is the only proper documentation that I can find on this. My car has both sensors, and they both lead into the cooling unit, and are sealed with RTV.

4. The four yellow wires on the left hand side of the harness represent the two temperature sensors. The two wires that are closes together represent one sensor.

5. There are two grounds on the harness (black wires)

6. The red wire on the harness provides power to the unit.

7. The green wire with the orange stripe is for output of both the A/C fan relay, and the loop that goes in the following order: Dual Pressure Switch > A/C Temp Sensor (compressor) > ECU. If you have a sensor that is not reading ON, then the A/C clutch will not engage. The A/C clutch binary value in DSMLink will be set to 0. With this controller, however, the A/C fan relay will be turned on regardless of whether the A/C clutch is engaging.

8. If you wish to test the circuit without the MB946485, simply unplug the harness and take a paper clip and plug it into the red and green/orange wires. The two temperature sensors will be bypassed and allow you to check out other sensors.

9. The MB946485 is a STURDY animal. Mine was acting a little strange, so I pulled the casing apart and found some corrosion between two of the solder pads. I cleaned the traced and pads up with acetone, and the controller ran like it was brand new.


I've now tested everything in my A/C loop with the exception of the compressor temperature sensor. Anyone have any good ideas on how to test or replace that sensor that doesn't involve taking half my car apart? I'm about to drop my t-case and look at it from the bottom, as there isn't much room in the upper part of my engine bay.

Good luck!
Matt

 

[97gst_spyder]

For the compressor temp switch, I do not think its replaceable. Now I've had the connector be loose and that cause no ac or intermitten ac. Also for the 95-96 ac buttons vs the 97-99 ones. They are not backwards compatible. If you use a 97+ one in a 95-96 you will only get Econ mode.

 

[Dyesuperman]

I found I had 12v to the A/C relay contact that provides 12v to the clutch. I did not have any signal to the relay coil that would close the contacts. I am not sure if that comes from the ECU or the A/C ECU.

I found that if I induced 12v to the A/C clutch the clutch would energize. I held it there long enough to get some cool air coming out. Since I did not know why the A/C relay was not working I wired in a switch to the clutch and flip on the switch when I want cold air. An inconvenience for sure, but at least I get clod air( I also converted it ti r134.

Bringing this back from the dead. Before I test voltage on the ACCU, does anyone know the answer to this question?

I have power to one pin on the relay connector, but not on any of the others to turn the compressor on. If we jump the connector the compressor kicks on and blows cold air. I have thought of just wiring in a switch like above but would much rather fix it correctly. Any ideas before I start testing the things stated in this thread? Somewhere I should start perhaps?