Kimreeder

New user here and please forgive me if this is a duplicate post. I've searched the site and I think some of this is repetitive and some is not. I'll try to give you the whole scoop at once so the issues are clear.

So, here ya go...

I own an '03 Civic 1.7 SOHC. Recently my A/C went out. The control on the dash worked (or seemed to), because there was no change visually. The yellow/orange light for interior circulation still came on, and the green light to activate the compressor still came on, but the compressor would not engage. So, I took it to an AC specialty shop. They told me my interior switch/module/control - whatever you want to call it was bad and only available from a dealer. No problem. $250 later I have a new switch but still no A/C. Was it really bad? I can only assume it was - old part has been tossed.

Then they tell me that there is power from the AC Compressor to the PCM, and there is power from the interior switch to the PCM and the failure is at the PCM. However, they do not work on PCM/ECM issues so they referred me to a dealer. Even with this info, they swore up and down that the pcm was in the fuse box under the hood and so the entire fuse box needed to be changed. They said they were 100% sure this was the location of the PCM which was different from the ECM on this particular vehicle. They said they knew it was the PCM because they ran a jumper wire bypassing the PCM and was able to get the AC compressor to kick on.

So, what the heck, I decided to change the fuse box. $60 from the salvage yard cant hurt. Cheaper that a diagnostic test right? I get to looking and think, "You know, there's no computer module here." but thinking that since these guys were so competent I figured maybe there was a break down in communication between the tech and office, I went ahead and changed it out. 15 minutes later.... No change.



So, I call dealership to inquire about parts only.

PCM Part needed is 37820-PLM-426 - a cool $1128.66. Nope, nope and more nope. I've been trying to save up and buy a boat. 1130.00 ain't happening.

Oh, and dealership guy says, "I'm looking at the wiring diagram, and there isn't any PCM at the fuse box."

So, I get on the phone and call the bone head at the AC shop...."Oh, my bad...I looked at the wrong diagram. The PCM is the ECM on this vehicle and it's under the dash, not at the fuse box."

No Joke. Thanks bro. That's ok. I'm not mad. I'm out over $300, but hey, maybe I'll have air by the end of the summer.

So ebay and salvage site search ensues and like I've read in other posts, it seems as though I can get a 100.00 PCM unit from a salvage yard that may not end in 426, but it seems that a 37820-PLM-L56 or L57 will work. That makes me a little nervous, but I haven't physically checked the number on my PCM so it might be one of those anyway.

Ok. So, now I'm thinking that if I can fix this puppy I might be able to buy that boat I was looking at last week instead of dropping a grand or two into my car.

Now, this is where it gets interesting, and keep in mind that I have not had it actually diagnosed by anyone who can definitively say it is the PCM other than the people at the specialty shop who by their own admission do not work on PCMs, and who did not know where the PCM was even located on the vehicle. (How they were able to bypass the PCM with a jumper wire without knowing where the PCM was is still a mystery to me.)

So, as if this wasn't enough of a fiasco, here are a couple more issues that may be contributing to the situation.

First - The starter has been very sluggish for a while so I took it to auto zone, thinking that maybe I have a voltage/charging issue that was becoming evident through all this. Battery isn't the newest I've seen, so that could be a problem right? Battery was holding a 95% charge. So, I changed starter. That problem done. This was within the last 24 hours. I figured before I took it to a service center I should fix what I knew was wrong. When I took the old starter back to get my core refund I asked them to run a scan test to see if the car had logged any trouble codes. (PCM Maybe) Nothing.

Second - A couple months ago, my stereo went out...sort of. Previous owner installed an Alpine Amp under the drivers seat, and you can either plug in to your smart phone and play music, or use the factory CD player. Now, before it went out, it worked great, and being as how the previous owner was my sister in law, whose BF works for a FORD dealer, they would have had it installed properly - and they've had it for a long time. However, every time you plugged in your phone, there was a loud "POP" through the system as you plugged it in. I assumed that when it went out, we had blown a fuse from one of these power surges because the radio itself still recognized that you were playing a cd or listening to a station but every speaker was gone. However, no fuses have blown in the vehicle or on the amp itself. The inline fuse coming off the positive terminal on the battery, the fuses in the box under the hood and inside the car, as well as the fuse on the amp are all good. Up to this point, the A/C has still been working. It did not go out at the same time as the AMP. I just thought that could be a contributing factor.

Now the A/C is gone.

These issues didn't all happen at once so it's hard to pinpoint one particular cause. So as it stands, I have no A/C, no stereo, a new starter which works REALLY well, and no trouble codes.

I also have not ruled out the possibility of demonic possession.

Your thoughts?

ezone

^^I found your problem right here^^


There is no computer anything in the engine compartment fuse box.

The PCM is in the dash behind the glovebox. If you have a manual transmission, it's then called an ECM. Normally they are reliable.
A GOOD scanner may be used to view AC input and output data as 'seen' by the PCM.

MICU or multiplex unit (Hondas name for the body control computer) is in the underdash fuse box.
Much of the time if there is a problem with it, there are many electrical problems at once. Courtesy lights don't work right, no key chime, no warning beeper when the headlights are left on, odd warning lights on the dash, AC doesn't work, wipers lost one of their settings, maybe more.




When you start the engine and turn on the AC, do both radiator fans turn on at the same time?

Kimreeder

So far there have been no other electrical issues other than the stereo and the a/c going out.

Kimreeder

I will have to check the radiator fans. I haven't noticed what they do

ezone

Need to know about this before I start thinking about AC.



Do you have a volt/ohm meter and do you know how to use it?
Do you know how to backprobe using a paper clip or a pin?


Can't comment on the radio issue. Drop a new cheapie radio in the dash? (DO NOT hook up any wires for 'illumination', or else it will get really expensive)

Kimreeder

The radiator fans do not start up when I start the car. Unfortunately I do have a meter, but I do not know how to use it. Electrical work is one of those things I've never been good at.

I do appreciate all the advice this far. I'm sorry I don't have better information. I may just have to break down and spend the $150 to let someone diagnose the issue. If it turns out to be the PCM, (it is an automatic transmission) then I may be able to get a salvaged unit instead of paying 1000 to get one new.

5.0Thunder

I think he wants you to check the fans when the AC **** is on, not just when the car is running. The AC forces both fans so it'd probably let Ezone know that the AC function is trying to work.

Kimreeder

Gotcha...I'll check that out. I can say that the air conditioning mechanic told me that there was power to the pcm from the a/c control - when the green light is on, and there is power from the pcm to the a/c compressor. But the compressor is not recognizing that the switch is turned on. That's why he thought the problem was at the pcm. Now to be fair, he thought the pcm was at the fuse box under the hood so that's where he saw there was no power. But that whole fuse box has been replaced so it's not there. Either way, it's not completing the circuit. But I'll still check on the fan radiator fans

ezone

Exactly. I need to know if turning on the AC system will cause the radiator fans to turn on.

I'm pretty sure I worded it the specific way I intended: When you start the engine and turn on the AC, do both radiator fans turn on at the same time?

The question retyped in red above is not just an example.....You answered "no", but you apparently missed the part about turning on the AC before checking.
Skipping parts of a question only leads to wrong conclusions.
The exact answer to an exact question is crucial information to me as a troubleshooter.
If you need clarification or don't understand my questions, just ask.


LMK.


Um....
Based on your story here I might guess that guy is only making some wildass guesses, and that's not how real diagnosis plays out.


If you are willing and able to do the work, I can probably help you figure out some real answers....You will have to read/understand/answer more than one question at a time in a post.
I may try to gather a lot of information at once to save time, so I sometimes ask several different things in one post, and expect exact answers to each.
I might even post other threads for you to review because I've probably made 15,000+ AC related posts in this forum already.