I am in the process of reverse engineering (to the component) the board inside the ICU. I have fried three of these in the past 6 years and it is getting harder to find replacements and they only seem to last a year or two at the most. With the availability of cheap/free pcb design tools and places like OshPark accepting prototype orders for as few as three boards it is completely in the realm of possible to get a working PCB design. There are a few hurdles in the process though. For starters I don't wish to do a ground up design project. I'd like to just replicate the design and get boards fabed, that is much less time and labor intensive. Unfortunately some of the OEM components are not available. The relay, IC, conenctors and audio transducer seem to be the main challenges. I have found suitable replacements for the relay and the transducer so some minor redesign can take care of those. The IC unfortunately isn't available and I can't even find a data sheet to try and source a replacement. They were likely custom runs for Honda by OKI. ICs would have to be salvaged from old boards. I am an accomplished electronics technician and have all the tools necessary to do the work. All of this is completely in the realm of possible now. So a couple of questions for the group.

1. Does anyone have a functional or at least non physically damaged PCB they would be willing to take some decent pictures of? I need the green/backside specifically. All the boards I have are charred and peeling around the matrix resistor so I can't physically trace the runs on mine.

2. Does anyone have anymore old toasted boards they would be willing to sell or donate to the cause? Remember I need to salvage ICs and connectors to make this work.

3. Is there enough of a demand to either offer slick unpopulated board at near cost or a refurb/refab service? I am not looking to get rich, but I don't have the time to be salvaging components and building boards for free either.

Open to any suggestions or feed back, especially board pics if there are any available. This is my first post but have used and abused you guys many times to keep the old red bullet running.

 

Are you talking about the white box on the back of the fuse panel under the dash?

I think there are two versions, an intermittent wiper version and a non intermittent wiper. I have what I think is a good intermittent version sitting on top of my tool box waiting to install. I could get you some pictures if that is what you are looking for.

The one installed in my car has a problem with the intermittent wiper function and sometimes smells like capacitor electrolyte.

When these fail what symptoms are you seeing?

 

The first thing I have noticed is the key in the ignition warning goes, followed by the intermittent wipers then the side marker lights start doing wild things which effects the turn signals as well. If you search ICU or integrated control module the problems are fairly well documented. Unfortunately with the exception of drilling some vent holes and possibly recapping the electrolytics we don't have a real good solution. That is kind of my aim to see if we can do something more sustainable than swapping in almost thirty year old parts with a limited life expectancy if you can find them. I included a thread below that talks about the preventative measures and I highly recommend at least the vent holes before you swap them out. Check the new one for bulging caps and charring on the traces on the back (green side) of the board. This board level damage seems to occur around the connector on the long edge of the board around a matrix resistor labeled RM1 adn over to the edge of the relay (black box in between the connectors). It looks like a long black strip that runs parallel very close to the connector. I would poke some vent holes in the case around that area. Any pictures would be greatly appreciated and don't scrap that old board! We might be able to salvage some parts! If you have any other questions let me know and I will answer as best I can. I have a dealer service manual for the 91, so if there is anything else you need from that its available. If you want to send pics let me know and I will get you my email address.

https://honda-tech.com/forums/honda-...odule-3206045/

That is it man. The part number is 38600-SH3-A111-M1. Mine happens to be gray in color. I am not certain if the color matters. There is also a large B on the part label. I have seen references to maybe the B denoting intermittent wipers, but I can't confirm that. I haven't seen anything to support that during parts searches in the past or my salvage runs to the local wrecker yards here. Any pictures would be greatly appreciated. You will have to separate the case to get tot the board inside. There are two small tabs on either side that hold it together. Just pry the case apart with a small flat head screwdriver at these tabs and it should separate pretty easily. The are of the board that i need pics of is on the back/green side, particularly the long edge around the connector and relay. I included a link to a thread on a CRX forum that you might want to read before you do the swap. Seems like old caps and heat damage to the board are the biggest failure items. Some symptoms include loosing intermittent wipers, open door and seat belt buzzers and eventual problems with the front side marker lights and eventual those mess with overall turn signal function. I can PM you my email for pics if you'd like. And save that old ICU! We might be able to salvage some parts from it.

 

 

hey I know this thread is old but I’m struggling to identify the matrix resistor for my icu. Where do I find one and what kind is it? This is my first time posting here. Very useful site for me for years though.

 

Have you been able to replicate the boards? Mine is officially a door stop.

 

Sort of OT, but when I dim my interior lights w/ the dimmer/adjuster, I get a burning / electronic smell in that area of the cabin. Could that be my ICU doing that?

 

It's part of the ICU. I WOULD CHECK YOUR BOARD.

 

Might be of some use to some. When/If I get more time to mess around with the thing I'll update this.

38600-SH3-A111-M1 LOT 1Y22 B



Schematic of the PCB attached. It's not 100% complete, being there's no information on the C1147 OKI chip in there, but given enough tinkering and reversing of how the car signals this thing and then what the ICU does in response, designing some cheap microcontroller to do the same thing wouldn't be incredibly difficult.

 

Oh snap. Great work!

 

That sir is very cool and will def help someone out.

 

This is my fix for the blinkers going wonky, my right indicator worked fine but my left indicator turned on my left bumper light but my right marker light and made the left one do a spluttery flash opposite it effectively giving me hazards up front when I put on my left blinker. After a scary left turn around a roundabout I decided to pull apart my icu and see what all the fuss is about. I found a bunch of burnt traces but all the components looked good so I "retraced" them. It didn't work. Then I saw RM1 was probably the cause as all the burnt traces kinda came from it. Then I found this thread and it has been immeasurably helpful as I wouldn't have been able to imitate, let alone know what the heck what the resistor matrix is. So I copied the design from the schematic substituting 22k resistors instead of 20k ones as that's all I had but it works now!
This is the only kinda before picture I have.


I put it on the backside because of the heat people are saying kills these. And I hadn't removed RM1 yet, I ended up wiggling it back and forth until it snapped off. And to put it in the case I slit a hole in the back long enough for the resistors to pass through upright then bent them to the case with some wicked double sided tape to prevent vibration from the long leads I left on them. So that's my frankenstein icu!

 

Good deal, but heat isn't killing anything in these. It's the Capacitors that get leaky from age and then that electrolyte gets all over the board that both eats them up as well as makes them conduct where they shouldn't. They should all be replaced on that board to keep it going as long as possible.

 

well, thats a bummer, I was really hoping to not have to touch it for a while. That makes sense though. I am now looking for capacitor replacements and am unsure whether to get a newer design or try to just imitate what is there. Also is there a way to know the resistances and current load of the caps on the board?

 

None of them are really anything special, so you don't have to get all deep into picking out some replacements with low ESR and this or that crazy ripple specs and such. The schematic has the voltage and microfarad rating for them, or just go by what is already on the ones in there, really all that's needed there. Maybe pick out some that are rated for 105 degree and have a high 'Lifetime @ Temp" rating, but anything new you put in there is going to be far better than the ones you take out. The only one that's different is C14, as it is a Bi-Polar Capacitor, ie it has no + or - side to it, so it should be replaced with another Bi-Polar type if it is.

 

I know I'm responding to an old thread, but hope you or someone else can respond. I need to acquire all of the replacement electrolytic caps for my ICU (9 of them from what I can count on the circuit board), and looking for recommendations on where to buy these online. I'm just trying to get the info from off the old caps and try to buy something that matches. Looking for an online outfit that sells these caps individually, so I don't have to waste money being required to buy them in packs. Any recommendations?

 

RDC_PCB created and attached a pdf schematic above in post #9.

Looks like the capacitors are:
C5 1 μf 50V
C6 1 μf 50V
C7 1 μf 50V
C8 10 μf 50V
C12 33 μf 35V
C13 33 μf 35V
C14 BP (Bipolar Capacitor) 3.3 μf 50V
C15 47 μf 50V
C16 100 μf 16V

Digikey, Mouser, Jameco are some places to get electronic component parts.

 

Fantastic! Thank you, tech8.

 

Question for you or anyone else: I noticed that the capacitors on my ICU board have the connection prongs splayed away from each other to accommodate the width of the connection holes. Are the capacitors only sold with the connection prongs that are straight, or are there caps that are available that are sold pre-bent like the [factory] caps on the ICU board? Seems like it could be some serious work & hassle just manually trying to shape form the connector prongs.

 

Some have the leads prebent, some don't, that's called the 'Lead Spacing', aka how far apart they are measured center of one hole to the center of the other. You don't have to bend the leads to some NASA tolerances, close enough is more than good enough there as they bend very easily.

Be aware C14 is a Bi-Polar, if you replace that one it must be of the same type. The rest are the pretty bog standard Electrolytic Aluminum type that are polarized, that is have a + and - side. I'd also get ones that are rated for 105c also. Nichicon, Rubycon and Panasonic are some of the better brands, but honestly, anything you put in there is going to be better than the decades old ones you take out.

Make sure the board is cleaned of any electrolyte that any of the old caps have leaked, as that mess is conductive and corrosive. Just a good going over with some rubbing alcohol and an old toothbrush or Q-tips will do.

 

Hey RDC_PCB,
Thanks for sharing your knowledge about ICU repairs.

Out of expediency I decided to get a replacement ICU in good condition, which solved my dashboard brake light issue. However, I would like to repair the original ICU to keep as a back-up. So, I have a few questions to ask about what I think I need to do and anticipate:

1. Do you have knowledge or access to the PCB schematics of the ICU that locates the position on the PCB where the dashboard brake light function is? I am surmising that the leaked electrolytic fluid has corroded and caused a cross-circuiting issue on the area of the PCB trace where the dashboard brake light function is located. This would be the section of the PCB I would want to repair first and foremost, if it is repairable at all.

2. There are 9 [cylindrical] electrolytic capacitors located on the board. Any idea what each of these capacitors' functions are? And do these things function even after the electrolytic fluid inside them have long since dried up?

3. Once I have replaced all the electrolytic capacitors, and all the PCB traces have been cleaned and still intact & hopefully functional, I would need to do a full test of all these capacitors and resistors to make sure there is continuity, right? How would you go about testing these? Is it a simple continuity test using the multimeter, or is there specific ohm settings that need to be selected to test each capacitor and resistor terminals? I am not electronically knowledgeable on matters like this, so your knowledge on this matter would be appreciated.

Best Regards,
E. Lee

 

I'd be opening up that replacement one was well. Even though it might be functional, the capacitors in it are just as old and replacing them before they get into that shape will be much easier.

1 - No idea how that thing could make your brake light come on. I wouldn't worry about any specific area of that board for the time being, as the entire thing is getting a bit rough and going in there to do one specific repair will ultimately be pointless. It's not the worst I've seen, but you'll most likely lose some traces when replacing the caps on that thing, so get ready for some PCB repair as well, which doesn't have to be anything fancy, just jumper wires to get things reconnected where needed.

2 - The schematic of this board is located in post #9. Once they leak to that extent their values change and they stop working correctly.

3 - The rest of the components are likely still alright, no way to guess better at that without seeing them. The schematic has most of the other values also, and as far as Resistors and traces go those can be tested with pretty much any DMM (Digital Multi Meter) that you choose. Testing cap values is another thing, but the new ones will be new and the other types on there don't tend to fail. Most components will not test correctly in circuit, and either need to be removed or at least taken part way off the board so they aren't in the circuit any more. There is really no point in digging into all of that until you have a more specific place to dig.

What I would do with that thing is clean it all up first. Just rubbing alcohol and an old toothbrush, go over it top and bottom until no more junk comes off it. Then give it a good look over for anything that's visibly damaged. Replace all of the Electrolytic capacitors. Repair any traces that need it. Then toss it in the vehicle and if anything doesn't work, then get into troubleshooting it.

 

Thanks for your recommendations. I just have a question about restoring connections using jumper wires. Would you be able to refer me to any kind of visual illustrations, like something on YouTube, that demonstrates a jumper wire connection procedure? I haven't done this kind of thing before [on a PCB], so it always helps to learn to do something by visually observing how it's done. Thanks.
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I used to work in a TV repair shop (back when people used to fix TVs) and a good soldering iron is very important. Its best to have one of the ones where you can set the temperature. Take good care of your soldering tips! Then one of the hardest parts is de-soldering the old parts. We used these copper wicks that would adsorb the solder when it was melted. There are also little solder suckers that work pretty well.

 

Thanks for the recommendations & video references.