DIY ECU refurbish

[DanHoug]

i just finished refurbing 3 ECUs and thought i'd detail things. one was an older 025 906 022 Dave had sent me that was flaky and 2 were newer "D" models from an 87 and 89. i didn't take pictures of the early model but the design was significantly different with many electrolytic capacitors that were replaced as well as a two piece heat sink that lacked heat sink grease. the "D" models only had 2 electrolyics and a solid block for the heat sink eliminating the two piece design and the need for heat sink compound between the parts.

here's the two newer ones:

unscrewing the case one can see the EPROM chip area is well shielded as well as the two capacitors that will be replaced:

here's a shot of the EPROM itself for those that do the deep dive:

while this failure point was NOT bad on my 3 ECUs, another Samba member, Alistair, posted these pictures of a failure of the solder points for the SCRs. excellent work! topside location:

and the bottom, red circled area was bad and resoldered:

to address that on my good ECUs, i removed the solder from all the heat sinked components and resoldered. here's a photo with the solder removed on those points:

i'll mention a solder sucking gun, about $300, makes board repairs soooo much easier. it makes a cleaner repair if you can remove the solder first in resoldering and obviously is great for component removal. i love this Hako Fr-300:

there's also a resistor that gets hot and scorches the board. i resoldered that too. replaced the 2 caps, both 100uf but one was 40volt and the other 25volt. use these 100uf 50volt caps from Digikey for both:

sometimes when the component is removed, the hole has stubborn solder that just won't suck out. here i'm using a #71 carb jet drill that was the perfect size:

that's about it... on the newest "D" model, address the heat sinked component solder points, address scorched resistor solder points, replace capacitors, DeOxit external pins for plug. on the older models there will be many more electrolytic capacitors to replace and one should put heat sink grease between the component plate and the heat sink itself. I still have Dave's unit that was flaky installed in my van and it is doing fine. I would wager this addresses most of the ECU failures.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[ALIKA T3]

Super interesting, thank you!
I know nothing in electronics, how did you determine the components were bad? Or are they preventatively replaced?
I have a pile of these suckers that need work, and one is a Shoebox Electronics tool I would love to use .

I opened some of them out of curiosity but was quickly deterred lol!
_________________
Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[DanHoug]

with anything this old, you ALWAYS replace ALL the electrolytic capacitors. they age and fail causing all sorts of weird issues. there are many other capacitors on the board... tantalums, polyester, etc but the round can electrolytics are short lived. forgot to mention you want to always order caps rated for 105C temperature and also the longest life in hours. higher voltage is fine to substitute but never lower. Digikey and other electronics sellers always specify this information.

i've got this old Mercedes i'm bringing back to life. the climate control box was restored as well as the cruise module by simply replacing the electrolytic capacitors. you replace every one you see on a board because they have a finite life.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[ragnarhairybreeks]

Hey dan,

Was i that found a bad joint on the power transistor. Being an electronics duffer, it’s hard to describe my elation at fixing it. The fault caused engine no run condition.
The newer ecu looks much easier to get full access. My ecu had the second board on risers and the risers had goop on the fasteners. Was way above my pay grade to try to get that board off.

Oh and I have an old merc in driveway, working on it too. The mb engineers must have been paid by how complicated they could make simple things

Thanks for this post dan,

Cheers

Alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[DanHoug]

Alistair! right! i'd downloaded the picts when i saw them but didn't save anything else. thanks for chiming in, it was a great post.

it looked like your ECU was an early one so if you ever tear into it again, put some heat sink grease between the plate the SCRs are mounted on and the finned heatsink. it just has 3 screws holding it onto the heat sink.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[Zeitgeist 13]

[DanHoug]

caps are so cheap that once you have the module down, just shot gun them all and replace. i think with shipping it was like $16 to do the climate control module.

but to directly answer your question, yes several instruments test capacitors at their rated voltage, and this is critical to check for leakage. the Sencor Z-meter series eg the LC53 checks both capacitor value and leakage at their rated voltage. less expensive but perfectly adequate models are the old Heathkit IT-28 with the 'magic eye tube' that i really like for both coolness and it gives a dynamic visual representation of the caps leakage and charge times. these go on eBay for well under $100, i think i got one for $25. i gave my IT-28 to a friend interested in electronics as i have the LC53.

many multimeters have a cap checker that returns just the value. useful but not a good test on vintage electronics, need to check for leakage as they age.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[fxr]

[a2wolfsburggli]

Do the ISM next please! I'm not running mine at all, it's in the glovebox. So if you need a guinea pig just shoot me a a DM. I'll mail it to you.
_________________
Current: '87 Westfalia | '16 Audi Q5 3.0T S-Line w/sport package.

Past: '09 CC 3.6L 4motion "R36 wannabe" | '02 Audi TT "ALMS Edition" | '84 Jetta GLI with Autotech Supercharger | '89 Helios Jetta GLI 16v's (x2) | '95.5 URS6 | and the list goes on.

Never underestimate the entertainment value of OCD overruling Common Sense

[DanHoug]

[DanHoug]

continuing on the ECU rebuild thread... i had fried an older non "D" model ECU by experimenting with a Delta Mark 10 C capacitive discharge ignition system on the vanagon. with the dead ECU, Mark (crazyvwvanman) had the excellent suggestion to follow with an ohm meter the coil trigger pin (25) on the ECU to the switching component mounted on the heat sink. that led us here, to the far left component screwed to the heatsink.

also notice the 2 piece heatsink vs the solid block in the "D" ECU. that far left component is a thyristor. thyristors are essentially 'latching transistors' that remain on once triggered until triggered off. typically high voltage and high amperage, like up to 12 amps. SCRs are a type of thyristor. so, fire up the Hako FR-300 and remove the little suspect.

a whopping $0.71 each at Digikey. 4 on order. stay tuned to see if we'll be able to name this ECU 'Larzarus'.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[ragnarhairybreeks]

Hey dan,

What’s your thoughts about the contact between the end cap heat sink and the vertical metal board the hot components are mounted to?

I can see traces of thermal paste, it’s the fit up good or iffy?

Alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[DanHoug]

[DanHoug]

Back From the Dead. the thyristor arrived today, i'm overnight close via USPS First Class for $4.99 from Digikey, and soldered it in. fired up immediately, took it for a 20 minute test drive and all is good. here's this early ECU, a few less refinements in design but i detect no drivability difference.

credit on this repair really goes to Mark. i do a lot of board level repairs but it wasn't in my fore-brain to trace the coil-fire connector pin back to the rack of transistors. great tip.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[ALIKA T3]

Nice job, I`m impressed !

If you`re bored, I have 6 of them to do
_________________
Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[SyncroChrick]

Very impressive and also a bit concerning...does that mean than most ECU needs some refreshing at this point? Since they have all the same age....

[DanHoug]

[dhaavers]

[DanHoug]

another successful ECU repair... dead ECU brought back to life with some pretty simple repairs: replace thryristor that controls the grounding of the fuel injectors, replace 2 100uf caps, repair heat damaged power resistor, resoldered harness connector header, cleaned up PCB of some light corrosion. put the ECU in my '87 and went for an uneventful 10 mile drive! this is where NOT having the ECU in that metal cage makes swapping these very easy.

here's the riveted thryristor which makes it a PITA to remove. i snipped off the head of the aluminum rivet, drilled out and ran a self tapping screw in with a nut to pin down the clip and allow the slight bump of the remaining rivet to protrude beyond clip. Loctited the screw in place.

burned high watt resistor

PCB side of resistor

_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[Klister]

But for the cost of that sodder sucking gun I could by a good ECU