Dried Caps in ECUs

[addo]

I'm pondering this one, electrolytics specifically.

I presume that the few seen in most ECUs are there for the characteristics they impart to a circuit, rather than any other reason.

What are the odds, that in an older ECU they are suffering from dried-up electrolyte and no longer possess exactly the qualities needed? As in, would one replace them as part of chasing mild faults that otherwise seem to have no clear root?

[spider]

I guess they could cause some odd faults, although I expect most of the elec's are there for their smoothing ability rather than anything else.

If its a small fault and you really are out of other ideas, then changing them might not be a bad idea at all. I guess you would find them in parallel (maybe) to a sensor input or two...

[HDI]

Capacitors can perform a variety of functions in electronic circuits, all of which are as critical as any other component. Failure modes can be various, short circuit, change in value, open circuit, temperature variable short, open or change in value, voltage variable faults, internal electrical leakage etc, etc. There have been issues with quality of some caps from the far east which have plagued many electronic devices for years but it's almost impossible to define which will cause a problem, when or if ever ! They can show physical signs of defects, bulging of the ends or sides and leakage of fluid. Many service techs for all types of electronics just change electrolytics as a matter of course now, to a known quality component.

[spider]

I did think about mentioning the mains smoothing ones' exploding, had a few of those in some old equipment I have (more about that another time) , but only really had one go with a real bang, the others just do a magic smoke trick.

[HDI]

That is a common failure mode with large value electrolytics if they haven't been used for a prolonged time. In those circumstances they should be reformed by gradually increasing the voltage across them until normal working volatage is reached. Otherwise they are liable to draw excessive current when suddenly woken up, then they can short out internally and draw massive current which causes localised heating and bang !