surface mount 10uF capacitors?

[eccerr0r]

I was trying to figure out why my 20-year old car's transmission won't shift unless it's warm outside (seemingly). It has an electronically controlled tranny. However there was just one 470uF 35V radial capacitor on the board. I swapped it despite it seeming to be ok, but that didn't fix it.

Oh well.

However there are still three 10uF surface mount caps (rectangular, polarized)... I wonder if they could also go bad.

Not sure what else could be temperature dependent, capacitors definitely fit the bill. Rest of the stuff on the board are resistors, ICs, multilayer ceramic smt capacitors, a relay, voltage regulator IC (series dissipative on heatsink, and seems to be outputting 5V just fine), power MOSFET (on another heatsink), ...

[stj]

Re: surface mount 10uF capacitors?

check for cracked solder joints - specially on parts that are fixed to something else like a heatsink or case section.

[redwire]

Re: surface mount 10uF capacitors?

I would re-solder the connector and any big parts, Vibration is hard on the boards. But it could be the mechanical (solenoids) or temp sensor.
How old is the tranny fluid?

[eccerr0r]

Re: surface mount 10uF capacitors?

The "large" still look well soldered. Fortunately it's only a double sided board, but unfortunately all of the ICs and semiconductors have custom part numbers on them, so I have to guess what the original part is.

It definitely is some sort of temperature relation which is very weird. One experiment that I did, after the warm up period that the tranny start working again, I opened the windows and cooled down the cabin as much as possible...and then upon next start, it stopped working properly. I let the cabin warm up once again and it started working again.

But I pointed a hair dryer at the TCU... it didn't start working properly...

Very weird. I can't rule out tranny problems vs electronic problems but the fluid's fairly fresh.

[stj]

Re: surface mount 10uF capacitors?

foto's of the board?

[eccerr0r]

Re: surface mount 10uF capacitors?




Looks like a lot of OEM renamed parts. The two heatsinked items look intact but I should go ahead and reflow them anyway...

[stj]

Re: surface mount 10uF capacitors?

try resoldering the 2 parts with heatsinks and the crystal and relay.

when i say resolder i mean remove the old stuff first, not just slap more ontop.

[clearchris]

Re: surface mount 10uF capacitors?

If you swapped the electrolytic already, my next suspect would be the relay. I have had a fair number of those go bad... They can also go flaky, working sometimes, sticking on, sticking off, etc.

Haven't really had a problem with any tantalum caps (the orange caps).