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Been getting Code 16 on my firm ride everything Ohms out so I decided to open it up and look.

Well first it smells like fish and around C12 is a discolored spot wondering if this is signs of a bad cap. Looks to be a 100µF 50v radial electrolytic
PIC

Am I right in thinking bad cap and just simple unsolder and re-solder?
 

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Been getting Code 16 on my firm ride everything Ohms out so I decided to open it up and look.

Well first it smells like fish and around C12 is a discolored spot wondering if this is signs of a bad cap. Looks to be a 100µF 50v radial electrolytic
PIC

Am I right in thinking bad cap and just simple unsolder and re-solder?
Hard to tell from the pic, but is it swollen? If so, heck yeh, I'd just replace it and any others that are swelled up and go for it; can't hurt if it doesn't work now!

 

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Is the top of the cap still flat? It has a vent 'X' on top; usually if it's bad, that will be bulging and/or torn.

The discoloration is probably where the glue that held the cap down before it was soldered in ran some in the conformal coating that's poured over the whole board.

Can you take a closeup of the resistor lead soldering, and the area around the cap?

What I'm looking for is:

  • Does it have a ring in the solder, slightly outside the solder meniscus around the leads? Remove coating around solder joints, resolder
  • Is the solder grainy or have voids in it? Remove coating around solder joints, resolder
  • Have the resistors/caps been hot? The resistors will change color, the caps will shrink the label down smaller; the label is heat shrink tubing with print... Remove coating around cap, replace cap with same size, rating, and voltage.

Fixing coated boards is a drag; to do much to it, you have to remove the coating.

"Flux-off" bought from Techni-tool works well for that. :)

Probe everything first; you'll need sharp probes to go thru the plastic conformal coating. At least it's probably an acrylic; if it won't dissolve, it's urethane. That can't usually be removed or fixed.



Check all the bigger resistors for value, and see if any of the diodes are bad.

What does code 16 mean? I can't seem to find a list...
 

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According to my shop manual, in 1991, a ARC/EVO code of 16 is "EVO Circuit Short".

I'd be checking the wiring to the EVO solenoid on the pump.

RwP
 

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Discussion Starter #5
EVO ohms good and so do pins 48 and 43
 

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Discussion Starter #6
Here is a better PIC of the area in question. I probed it with my meter and the coating on the PCB just disintegrated.

None of the resistors are discolored and ohm ok. Though none of the caps look like they have blew the only other questionable one is the brown one behind this cluster of three but it looks more like a drop of that coating that is on the board.
 

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Here is a better PIC of the area in question. I probed it with my meter and the coating on the PCB just disintegrated.

None of the resistors are discolored and ohm ok. Though none of the caps look like they have blew the only other questionable one is the brown one behind this cluster of three but it looks more like a drop of that coating that is on the board.
Heh. That cap blew its wad all over the board; good diagnosis the first time.

Is that board NOT covered with a clear plastic liquid layer?

My IMRC controller didn't have any; I haven't had anything else fail to take apart, lol.

I'D Coat everything in conformal coating, if it were my design, but it's more expensive. About $0.20 in volume, lol. That probably saved Ford millions, thinking about it. :facepalm:

See the ring in the solder around the 1100 ohm resistor lead, beside the diode?

Hit all of those solder joints with fresh solder; I use Kester 44 60/40 for repairs. It will solder almost anything. Don't clean it with alcohol. :) Flux off, alpha cleaner, etc only.

Replace the cap; it probably has to do with one of the rate sensing circuits, since it caused a fail.

It being a 50V 100uf cap; the 50V makes me suspicious.

Unless there's a switching power supply somewhere, there's not that much voltage anywhere. :)

Cheap being the operative word, it was probably to alleviate a problem with that cap exploding; which is probably going to be a common problem for all of us, eventually.


This would work fine, and would probably never fail. :rofl:
http://www.digikey.com/product-detail/en/KHD500E107M90C0B00/565-3277-ND/2095891
~$40 :)

This is more likely what Ford bought; hi-rel, high ripple current.
http://www.digikey.com/product-detail/en/50ZLJ100MT78X11.5/1189-1662-1-ND/3134619
~$0.50


This is what I'd buy; overrated, and hi-rel.
http://www.digikey.com/product-detail/en/EEU-ED2E101/P13529-ND/1086755
~$2.00


The cap on the circuit board is definitely bad; I wouldn't spend much on components until you know it fixes it.

Cheap will last as long as Ford's did, lol.

Good diagnosis! The gloss in the pic threw me off; there was no Coating, and I don't believe that cap was ever glued down, lol.
 

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Discussion Starter #8
Yeah it has a coating on both sides. What is the best way to remove it and does it need to be replaced? I have a can of Electrical cleaner and on the CCRM I found it does dissolve this coating.
 

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Yeah it has a coating on both sides. What is the best way to remove it and does it need to be replaced? I have a can of Electrical cleaner and on the CCRM I found it does dissolve this coating.
I'd buy a spray can of flux-off, and a spray can of humiseal conformal coating, personally. It may or may not be available to you, so, YMMV.

Acetone or alcohol will likely remove it easily, but it also isn't good for anything else in there, lol.

The whole concept of repair is "Don't break it more than it's already broken."

You will be amazed over the next few decades how often something you do has unintended consequences. :rofl:

It's an acrylic coating; flux off works well based on my experiences with it; and you can recoat something that's been cleaned with it. This is important, as you might imagine. Not everything is, so test it. :)

A can of each will last for years, so if you do electronics, you will need it.
 

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Just had a thought. If you've never done a bunch of soldering on muli-layer boards like this, you might want to get some help. Make sure you get the solder hot enough to pull the cap cleanly - if you have to pull it hard, DON'T.

Not trying to get in the middle, Grog is doing a great job of helping you with this!
 

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Available yes, economical no. At a $50 min order any one else want a can? :D

I'll use what I have sparingly an give it a whirl.
 

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Just had a thought. If you've never done a bunch of soldering on muli-layer boards like this, you might want to get some help. Make sure you get the solder hot enough to pull the cap cleanly - if you have to pull it hard, DON'T.

Not trying to get in the middle, Grog is doing a great job of helping you with this!
This is good advice!

It's amazing all the stuff you don't think of to mention... :)

If you pull the 'barrel' out of a multilayer board, you're *'ed. To fix it, you need a copy of Ford's PCB drawings, lol.


Available yes, economical no. At a $50 min order any one else want a can? :D

I'll use what I have sparingly an give it a whirl.
Cool, I completely understand. :)

Final net hairspray used to be pure lacquer; It worked great. :) Find something similar, or use clear rtv to coat it.
 

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Available yes, economical no. At a $50 min order any one else want a can? :D

I'll use what I have sparingly an give it a whirl.
You can get the cap at Radio Shack or maybe another supply house like mouser.com (I'm not sure what kind of minimum order structure they have, if any).

If you have one, great; I'm sure I have one around here in my electronics organizer - it's a common value.
 

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Got any trashed electronics around the house? :)

That's where I always look first... Bad computer power supplies, etc.

You need a 100uF, 50V or higher cap of any type; aluminum electrolytics like that aren't anything special.

Although, Judging from how it failed, a high-frequency type might be good.

These guys don't have a minimum order:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=020-1664

This cap would be fine. :)

I'd order a few; there might be something else to fix, and take it out again.

These guys have some nice stuff; just don't go for the $50 RCA connectors, lol.
 

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Discussion Starter #15
Hit up RadioShack picked the Cap for ~$2. Was a pain to desolder but it works now just fine. Only issue I saw was the 85°C max temp v. 100°C + rating.
 

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Hit up RadioShack picked the Cap for ~$2. Was a pain to desolder but it works now just fine. Only issue I saw was the 85°C max temp v. 100°C + rating.
If it fails again, you know what it is. :) The 85 vs 105 thing is a spec that probably would lie on the same curve, if we knew the numbers, lol. The 105 one is probably guaranteed 25% of the lifetime time the 85 one is; half as long for every 10C. :)

Desoldering; I always cut the old component out, leaving the leads as long as possible.

Hit the remaining lead with fresh solder, and QUICKLY grab the lead with a pair of tweezers and pull it out while still heating the solder pool with the iron.

That whole operation needs to happen within ~3 seconds to not damage stuff on a multilayer board. :)
 
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