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chriswh86

Sam unit repairs - Soldering cracked

5 posts in this topic

So when I purchased my used 06 Smart Fortwo it drove great around town. The first trip out of town I took i started to have what seemed like a random stalling issue. It always allowed me to restart after about 30 seconds when you could hear the Sam unit reset. I drove the car like this for a couple months trying to figure out exactly how I could replicate the stalling issue.

 

 While I wasnt able to figure out exactly what was causing it, I was able to read a code P0087 which was a low pressure fuel pump issue. I wasn't going to start randomly swapping out parts and knowing that the sam unit is a common problem, that was the first thing for me to check out. I also found paperwork in the car after cleaning it out and it turns out the previous owner was having stalling issues as well and had dumped nearly 1000 canadian loonies to multiple automotive shops to try to find the problem.

 

IMG_20190717_1501042.jpg

 

Here is the SAM unit pulled out and on the table for disassembly.

 

IMG_20190712_2025219.jpg

 

Opening it up like a book to get into the pins on the back of the boards. My first stop on the back of the board was the 11-3 plug. As show in the photo below, you will notice the straight line of 12 solder points. This is the back side of the 11-3 plug. Do you notice anything wrong?

 

IMG_20190712_2025304.jpg

 

The right 3 pins appear to have actually broken and separated from the board. I took to re-soldering these 3 pins and other ones of concern around them. After re-assembly, the car is running great with no issues and any speeds!

 

To re-cap my issues and to hopefully help other folks:

 

 My car would drive fine for what appeared to be any distances at or under 50km/h. I had one stall out of 50 under that speed. When I would drive above 50km/h it would seem I could drive for random distances, some days all the way home but typically it would stall on me. I was starting to think cold days were better and I could drive further or all the way home without issue. Hot days seemed to trigger the stalling issue more frequently. After stalling if possible i tried to drive slow and that usually helped. I started to tap the sam unit when driving was good and only once did I tap the SAM unit and the car stalled at the same time. I wasnt able to replicate it again but I think the first time I tapped the unit and it stalled i must have hit the 11-3 plug.

 

Now looking at what the issue was and the symptoms I was having I am assuming that driving faster created more heat in the SAM unit and eventually lead to the pins disengaging from the board and the car would stall. I dont think vibrations caused the stall but it is possible. Either way, if you are having stalling issues have a look at your SAM.

 

I am happy to dig into a SAM unit for you as well :)

 

Chris,

 

IMG_20190712_2032594.jpg

IMG_20190712_2033151.jpg

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I did one last week on the same line of pins, 5 were no good if not more. I simply solder sucked them clean then resoldered them. It didn't solve the issue, as the plug is badly burnt also. We were hoping it would solve the problem, now we need to jump the power using relays to repower what we need.

 

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Alex did a good write up on this one that helped me immensely with the same problem (our CDI died the day after we bought it back in I think 2012).  The simplest solution is to re-solder that pin as Willy's says, and solder on a wire to it and carefully route it out of the SAM box and bypass the harness so you can attach it directly to the wire going to the fuel pump.  Essentially some cheap bugger used a wiring harness that can't handle the current from this (and the headlights really) and it eventually builds up corrosion which increases resistance and heat that fries the solder joint.  I eventually re-wired around two of the headlight pins as well.  Find somebody with decent soldering skills if you don't have them yourself (I made a mess trying to do it myself, but a friend at work cleaned it up for me).

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The wiring harness is fine - the stupid thing is putting the full amperage through the SAM.  So the solution if the SAM is not toasted totally is to mount three external relays.

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My experience with a badly water damaged SAM is that condensation in cold weather or airconditioning accumulates on the wire harness and wicks into the SAM connectors causing corrosion which leads to increased connector resistances resulting in heating and other issues.

 

My situation was compounded by having a weak improperly vented 12V battery which I frequently charged with an external 12V supply which resulted in sulfuric acid fumes being released into the car. Over a period of time this completely ate away at a number of metaliic pins on one of the IC chips in the SAM.

 

After repairig my SAM 6 years ago I inserted a sponge on the upper side of the SAM between the wiring harness and the SAM.  Parked outside in extremely bad Toronto weather for the past 6 years, no further problems.

 

Many seem to feel that a leaking windshield causes these issues. I don't.

 

http://clubsmartcar.com/index.php?/topic/27439-some-information-which-may-help-others-repair-water-damage-on-their-sam-circuit-board/#comment-316230

 

Edited by smartdriver
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