Here's my info
160 K miles
key on 48.5
Buzz 47.5 then 48.5
start 48.5

question: when pulling a grade at 65 mph volts drop to 44,45,46
Sometimes as low as 37. Is ficmgood or bad? _

 

Anytime the voltage drops below 46, something in it is bad. Time to sent it off the FICM repairman.

 

Let us know if we can take care of you - there is no doubt that your FICM needs to be serviced. The voltage drop under load is one of the tell-tale signs that it is on it's way.

Sorry...

 

Fellas did this not go as intended. we have done many repairs to automitive,aviation and residential electronics so we decided that the repair procedure is pretty straight forward. IDK what base material of the ficm board is clad with but I hit it with my standard 50w torch and it never would stake the caps back. We had a large time trying to get the original solder to reflow so we just sucked it out and started over. I also figured I would test the caps while I was there or even upgrade the 50s. Im not sure how hot you should get this paticular part since my experience with things in the past soldered right away with minimum dwell time. This thing got so hot it actually discolored the glass on the board. My hats off to you fellas that got good results. We did get them on, but they are a cold joint and Im not getting it back to the customer since its a rescue truck.

 

sounds like you're not using the proper soldering techniques! Prefered would be a temp controled iron with a proper sized tip for what you're working on. Note that the board has many small holes in it, these are what are called "vias" which not only provide an electic connection to other layers of the board but also provide heat conduction to the other layers. So... in short its a very good heat sink! For this application I prefer silver solder with the appropriate paste and have used a 40 W iron (not heat controlled) without any problems or discoloration of the board. I'm not positive but I assume it is cheap FR4 board material.

 

You may be correct, but I was beside myself at the way this componant reacted to heat. It could very well be the iron, it was a 50w controllable but Ive had years of success with out issue. We just took a stab at it anyway and will try later as it seems these are starting to poor in. We shall figure it out, I have I&E tech in the shop thats had years of experience too, and he doesnt like the board either. I scratched some of the cladding material off of the board and showed what appears to be copper. It soldered like a champ just couldnt get the cladding to accept the solder.

 

The board has a protective solder mask on the copper cladding but not on the component pads. From what you describe sounds like your board is contaminated if you can not easily solder to the component pads.

The board is a very simple basic design which works fairly reliably considering there are a few design issues which any electronic tech worth their salt can easily figure out. Doesn't sound like you should be attempting the repairs yourself if you are having all the difficulties you describe, leave it for the pros!

 

I understand the content of your text, and for 39 yrs weve done quite well. Normally would never mention the described failure however just finished a 7 pin repair and it worked like a champ. We used the same process as the first. I also canibalized a dorman card that we use and same results. No problem, this could be a fluke I understand. So now Im off to check my salt balance

 

I don't know how many people you have helped with this post, but I have to say you saved me hundreds of dollars. I had to do it twice before it worked, probably something I did wrong the first time. Thanks for sharing!

 

If I remember correctly the board has a metal substrate. It is a huge heat sink. Use 150W soldering iron set to 680 - 690 degrees, RMA (Rosin Mildly Activated) Flux, and 63/37 (Tin / Lead) Rosin core solder. Precise application of heat is required. Temperature can be controlled through the use of a variac.

Clean up with Isopropyl Technical Alcohol. The plating that you spoke of is attached to the board, on the surface some times with epoxy or other adhesive. It can also be etched. In any case, prolonged application of heat will break down the adhesive (at about 450F epoxy starts to turn to a white powder) and the solder run will "lift".

Properly performed, the application of solder or the removal should take no more than 3-5 seconds. Past five seconds, depending on the heat at the tip of your iron, a heat sink will rapidly pull heat away from your work area below the proper temp to melt solder and the circuit board layers or substrate begins to show signs of over heating.

The ideal tool for removal and replacement of the SMD (Surface Mount Device) is a SMD desoldering tool with the appropriate sized square tip. It fits down over the component, heats up the solder joints on both sides and allows you to lift the component off the board, quickly.

Most people are not going to have this type of tool. Pace Inc is one company that sells Solder rework stations. I have used their PRC-2000 and MBT-250's. Both of these units have the tools I am speaking of.

If you are familiar with the removal and replacement of components at the board level and are comnfortable doing it, than this project is not a bad one to do. If you are not familiar with removal and replacement of components or soldering on a circuit board, it is easy to make a very expensive mistake in a very short period of time.

 

Drquad, first of all thanx for the info, did it and it worked, only prob is now i get a new code of p2552 ficmm circuit throttle/fuel inhibit circ. truck starts and runs fine just wanted to know if youve ran into this.. thanks again

 

Thanks for the info guys. Mine tested at 20.5 volts with the key on so i discontinued the test. I pulled it out and repaired as suggested, now i get 48.75 and only drops to 48.5. Now that i cannot trust this ficm i thought about an analog guage for it but the only way that i can see is to put a hole through the cover with a molded wire/grommet to the 48v pin. Anybody else ever thought of this? I have heard the scanners can be unreliable

 

jswartz84, Others have done this but personally I would not recommend due to potential for fluid/water contamination of the circuit board should a leak occur. You might want to make sure it was sealed real good with a automotive grade silicon RTV.

 

Dr. Quad you are my new hero!

I had been having some cold start issues, I was in denial, I knew it could not be the dreaded FICM. I had the wife in the truck, 48v ignition, 12.7v cranking, that kinda settled that. Well I pulled it out, which was by far the hardest part of the operation, them dang plugs are hard to get to. Opened it up on the kitchen table. As I was pulling the staking off low and behold one of them tiny resistors came right off embedded in the yellow staking. That was the part I was most afraid of soldering back on. I just laid it back there and hit it with the iron, no added solder although I did have the iron tinned. After it cooled I picked at it to make sure it was stuck down well. I hit all the recommended spots, 16 on the back and 8 on the front. I also found if you keep all the staking is melts fairly easily with not much heat. I made a little spoon out of tinfoil, melted it over the stove (without the wife home), and poured it back over the electronics. After it cooled it had the same consistence as before it was removed. I figured that was better than RTV, my second option. Put it back on the truck and it fired up better than it has ever run before.

I figure I have less than $15.00 in the fix. That was buying my $3.99 Harbor Freight soldering iron, $7.99 worth of silver bearing solder at Radio Shack, and a few bucks for some cheap Torx drivers. Cost less that the Motorcraft oil filter from Walmart! Can't beat it with a stick.

az

 

Thank you for this resource! I plan on tackling this in a couple of days. I too have dropped voltage when cranking.