Should capacitors on old ECM be replaced?

[Dave9]

if equipment containing electrolytic capacitors, typically found in its power supply, is used often the capacitors will not dry out and fail. If they do go dry, they can be "reformed" using a Variac.

You are confusing two different failure modes. Electrolytic capacitors can dry out over time and fail, but this does not happen from lack of use, happens either way, somewhat faster if it sees a lot of thermal cycles or perpetual high heat.

Instead, lack of use for long periods (years at a time) with aluminum electrolytic caps causes a breakdown of the oxide layer on the aluminum foil and they become electrically leaky. This can cause rapid overheating and failure, and a lesser temporary concern is a capacitance drop.

It is this oxide layer that you'd restore by applying a low voltage over time with a variac lower voltage supply, but that will not recover a capacitor that is too dried out.

 

[willbur]

You are confusing two different failure modes. Electrolytic capacitors can dry out over time and fail, but this does not happen from lack of use, happens either way, somewhat faster if it sees a lot of thermal cycles or perpetual high heat.

Instead, lack of use for long periods (years at a time) with aluminum electrolytic caps causes a breakdown of the oxide layer on the aluminum foil and they become electrically leaky. This can cause rapid overheating and failure, and a lesser temporary concern is a capacitance drop.

It is this oxide layer that you'd restore by applying a low voltage over time with a variac lower voltage supply, but that will not recover a capacitor that is too dried out.

I somewhat agree- lack of use still does this. you're right about the oxide layer but passing current by use keeps the oxide layer useable. Either way, use keeps the cap useable, disuse does not
Thanks for looking it up on AI

 

[nobb]

If they are potted with an epoxy, then I would say don't touch it and wait until they actually become a problem since you risk damaging the traces when trying to replace. In this case it might even be worthwhile to get a spare ECU and attempt to recap that.

IMO if you get a spare ECU, the caps are going to be of similar age anyways so treat it as a practice board. Also, keeping it in storage unpowered for too long (decades)...may damage the caps in a manner that would require reforming.

In a modern car with a ton of electronics everywhere including the integrated infotainment, I cant even imagine how people will attempt to service these parts in the future.

 

[Snagglefoot]

Rock Auto sells remanufactured ECUs from Cardone and BSE for 1991 Toyotas.

 

[Dave9]

I somewhat agree- lack of use still does this. you're right about the oxide layer but passing current by use keeps the oxide layer useable. Either way, use keeps the cap useable, disuse does not
Thanks for looking it up on AI

No AI needed, I learned this decades ago and keep an (aging) stash of capacitors for repairs and new projects, though I've never had an ECM that needed them replaced.

 

[TomYoung]

This is a shocking question..... I'll see myself out.

 

[Dave9]

I somewhat agree- lack of use still does this. you're right about the oxide layer but passing current by use keeps the oxide layer useable. Either way, use keeps the cap useable, disuse does not
Thanks for looking it up on AI

We need to get back to the relevant information.

This is not about ego but rather keeping info useful. There is no somewhat agree. You're just wrong.

Let me be clear: Not using a capacitor does not cause it to dry out faster.

I would have never thought that I would be in a situation to call you out on this, except that it's highly relevant to the topic.

This was like electronics engineering 101, 40 years ago. Yeah, I'm that guy.

 

[willbur]

We need to get back to the relevant information.

This is not about ego but rather keeping info useful. There is no somewhat agree. You're just wrong.

Let me be clear: Not using a capacitor does not cause it to dry out faster.

I would have never thought that I would be in a situation to call you out on this, except that it's highly relevant to the topic.

This was like electronics engineering 101, 40 years ago. Yeah, I'm that guy.

This is not covered in EE 101, Bro. Seems like its your ego - not mine. The point is a device in use will preserve its caps- disuse , no.

 

[dnewton3]

Guys - let's not bicker.
State your position and move on.

 

[Lubener]

Rock Auto sells remanufactured ECUs from Cardone and BSE for 1991 Toyotas.

That is a good option if someone does not have soldering skills and feels uncomfortable working on pc boards..

 

[Zaedock]

Replacing caps on OBDI Jeep Wrangler ECM's is pretty common. I replaced mine a few years ago and it worked pissah.
I also replaced the caps on my spare ECM that had sat on the shelf for years.

 

[paulo57509]

For those that DIY:

• https://www.digikey.com/
• https://www.mouser.com/
• https://www.newark.com/

Are thru-hole caps are getting hard to source? Any insights?

 

[martinq]

For those that DIY:

• https://www.digikey.com/
• https://www.mouser.com/
• https://www.newark.com/

Are thru-hole caps are getting hard to source? Any insights?

I'm putting in an order next month but haven't had any issues so far.

 

[Rmay635703]

I’ve read time and time again that capacitors don’t last forever, but I’ve never witnessed capacitors fail on vehicle ECMs. I have a 1991 Toyota ECM. The capacitors are not bulging.

But I’ve seen damage caused by a burst capacitor. Looks like it can take out an entire board.

I guess my thoughts are, maybe the capacitors on these old 90s electronics are so good, that they should not be replaced. Maybe the quality was so good that replacement capacitors are greater liabilities.

has anyone ever replaced the capacitors on an engine ECM? Or do the OEM capacitors just never seem to fail? I mean, the internet says capacitor lifespan is 10-15 years, but mine are 37 years old and show no signs of failure.

Specific vehicle components even inside abs systems are getting el toro crapo with no replacements on old vehicles. It is a big problem but is usually covered up by swapping parts.
Older 3800 GM products are having some rather famous mechanics put them onto not recommended because various electronics are non repairable and not available new including abs system components. Just because you may find a guaranteed part from a source you like does not mean it’s a good idea as it’s unpredictable when it will fail again.

Cap replacements (amongst other things) could be helpful but these things are encased in random potting compounds which make repair extremely difficult.

My 2000 Honda Insight has some siblings that have had the dcdc fail due to corrosive leaky capacitors , one of my insights had a non-repairable immobilizer issue (both the ring, harness and ECU plus ??? All had issues). I ended up tearing the immobilizer off the ecu board disabling it because replacing rather horrifying parts did nothing)