Newbie recapping 1997 Dodge ECU - Advice please! - Page 1
Forum section: electronics / beginners

author: JohnnyTrucker
author_rank: Newbie
timestamp: July 15, 2024, 07:53:27 pm
content: Hello, I am very new to a lot in the electronics repair world but I have some basic knowledge/experience about soldering and capacitors and generally how a circuit works and such. I have a fair bit of experience with automotive stuff as well.I am working on recapping my 1997 Dodge ECU. I respect that some may disagree with that, but I have made up my mind on that. I have seen and heard of too many others with same and other makes/years that the liquid caps have already damaged or ruined the board so I’m not waiting for that to happen. This is a vehicle I am keeping long term.It sounds like there’s a general consensus that even the best liquid caps can’t be dependably counted on to last more than about 20-25yrs, at best. So I have also decided I will be switching from liquid electrolytic to solid, either polymer or ceramic so I don’t have to do it ever again, hopefully. Some may disagree with that as well but it’s what I have decided. This specific ECU was not designed for future maintenance in mind and recap like many other makes/years are. It was not designed to be able to have it taken apart multiple times throughout the lifetime of the vehicle. My guess is, it was designed to sell a vehicle at a minimum cost to the manufacturer. The ECU was easy to remove from the vehicle but opening it up was a huge chore, putting it back together will be nerve wracking probably and I’m not sure it would survive a 2nd recapping.The vehicle is important to me so I want to take care of it for the long term.My hope and plan is to replace the old liquid caps with caps that will allow the ECU to function normally, and last…forever..yes let’s go with that, forever!The original caps are (3) 25v 220uF 105C.My 1st choice of replacements is these: (dipped ceramic)https://www.digikey.com/en/products/detail/chemi-con/KTD250B227M90A0B00/6189620They are pricey but a refurbished ECU is much more pricey and may be in a more questionable state than my current one and I will likely need to go back and forth with the dealership to get it programmed right for my exact vehicle. I’ve read the stories of how this goes.Anyways, my question to the pros here at EEVblog is will it work? Setting aside my decision to pay the bill and whatever I need to do to get them to physically fit, will these caps work? It says they are rated for automotive and even mentions something about the AEC-Q200 cert in the datasheet. They are said to be long lasting and highly resistant to humidity, which is my main concern with my 2nd choice. They are not in the same form factor as my 2nd choice, but if they would function well enough like the originals, I could make them physically fit in the case.My 2nd choice is these: (solid polymer)https://www.mouser.com/ProductDetail/661-APSG250E221MHB5SThese are much more affordable and they would be easier to install as they are the same physical size and form factor as the originals, but they aren’t marketed as for automotive, just general purpose. These are also said to be more prone to humidity damage and being in a vehicle ECU, will see lots of harsh humidity and higher temps. The ECU case seals shut but there appears to be a small vent port in the back and I would be concerned about humidity deteriorating these and shortening their lifespan. The only way I could see these as an option is if I could somehow seal them off from humidity. Can they be coated and submerged in silicone like a thick conformal coating or caulking or do they need to vent and breathe? Could I plug the ECU case vent?I saw a guy on youtube recap his old Ford ECU liquid caps with solid polymers a few years ago and he hasn’t had any issues. I also chatted with an individual who said he has worked for over 30 years for an aftermarket automotive stereo manufacturer as an electrical engineer and he said they have never had a cap go bad using solid polymers and none of them were rated for AEC-Q200.I’m pretty sure either would work out fine but I don’t have knowledge or personal experience with this stuff.Please let me know what you think, thank you!

author: tggzzz
author_rank: Super Contributor
timestamp: July 15, 2024, 08:45:00 pm
content: A few general, arguably obvious, points for your consideration..."Automotive grade" isn't well defined, but shouldnt be ignored.Any replacement operation carries some risk, to be balanced against the reward.In some cases too low an ESR is as problematic as too high an ESR.Practice with the same tools on similar components in a similar board, before attacking somthing important. You will learn!

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 17, 2024, 02:00:51 am
content: I have not sub'ed to these type parts but if others have and they worked and lasted then they have answered your question.I am surprised that any control modual only has 3 of the same value caps?Also note most vehicles contain many moduals and many of those have failing caps.Jeff