When I did my IDM mod (bought a low mileage used one to modify), back in April, I used the low melting temperature rosin core solder the was included in an inexpensive 25 watt pencil type soldering iron kit. I used the smallest tip that was included in the kit. I scraped the sealant from the old resistor with a pick before melting it loose. I tinned the connections with a little more solder and held the resistor (bent in a "U" shape) with a small screwdriver onto the connections. I applied heat with the iron and let it 'melt in'. It took very little heat and the solder melted pretty quick, I cleaned the area with alcohol on a Q tip and they applied some clear RTV silicone over the resistor and connections as a sealant. I used some polyurethane roofing sealant to reseal the case and let it cure for a few days, since I still had my original IDM in the truck. Pictures, that might help, of this in the first mods album in my gallery. No problems with the soldering, sealing, or installation. It's been working great ever since.

Mueckster,

The only place you might have gone wrong was the use of the RTV on the resistor as "sealant". Everything else was perfect.

Most commercially available RTV contains acidic acid. It's outgassing is what causes the RTV to cure. This acid isn't good around copper, either. If it has the familiar "vinegar-like " smell, it's got acid.

If you're going to use RTV, a much better kind is that which cures by the absorption of moisture from the atmosphere. Unfortunately, it's not readily available. Dow-Corning 3140 and 3145 are good examples. Cheap, they ain't.

A clear lacquer-like material called "conformal coating" would have been the optimum material to seal the board itself against moisture. These are usually acrylic or urethane based.

I know this doesn't help much, now that it's done, but there's always a next time.

BTW, I wouldn't use the "low-temp" (usually eutectic) solder on the resistors used to fix the overhead displays in our trucks, as it is the high heat from the resistors that causes these joints to fail. But that's another discussion, for another problem, on another day.....

Pop

Now, you tell me! LOL I didn't think of that, at the time. I used very little RTV and let it cure before installing the cover. I think it will be all right. :) The amount was so little that it cured pretty fast. The soldering kit was for electronics and not really sure of its type. Time will tell.
Thanks for the info, Pop.
Bottom line: Don't listen to anything, I said. I don't know what I'm talking about. :-huh

I SURE didn't mean to imply THAT! Like I said, everything else is perfect!

If you ever have any problems with the IDM, however, that's where I'd look first, that's all....

And you probably won't.

Pop

No offense taken. :) This has been a learning process and I don't want to steer anyone wrong. I was a little sarcastic :rolleyes: with my comment. It was meant jokingly. Bad choice of words on my part.

So Pop - what is the best sealant to use on the new resistor and circuit board that is readily available?

I'm hoping to do this by the weekend and what to do it as right as possible the first time!

Thanks,

That I don't know. I just keep some of the right stuff around. 3145.

Keeping it as completely away from moisture is a real trick. In a baggie with desiccant in the fridge will prolong its life, but every couple of years I have to replace it.

I suspect any that doesn't have that distinctive "vinegar" smell would be "close enough".

Pop

Did some checking today and the closest I can get the DC 3140 or 45 stuff is from SLC, Utah. I want to get this done this weekend so don't have time to wait for stuff to be shipped. I'm going to go looking around town tonight and tomorrow for something that's close enough.

Thanks for the input.

How about some good old 3M 5200 marine adhesive? It's a polyurethane adhesive, and it dries by absobing moisture in the air. The only problem with using that is you would basically be sealing the IDM for life. They do make 5200 remover, but that stuff is very strong no matter what you use to get it off...

Thanks guys this answered alot of my questions about IDM's but I still more digging before I ask any more.:-tap

did anyone have of their fuel economy change? more fuel injected per event would make me wonder:-huh

Bump on the question about effects of the resistor mod on mileage; noticed it asked several times, but never answered. Sure, opening the injector more quickly and for a longer interval will give better response and power, but does this turn into a lower MPG due to the ‘fun-factor’ with the skinny pedal?

wow intersting thread spanning nearly 4 years. So now that there has been enough time to see how it works in the big picture is it really worth it, and does any of the original 8 still have some resistors left over??? I am in if I can find an IDM.

IDM
 

I used Swamps Diesel modified IDM

It was a part of my troubleshooting a problem with engine performance.

Seems to have added some performance and made the injector buzz test louder.

I don't have any mileage figures to compare with.

I'm still running my modded IDM without any hiccups at all. If I behave myself I can get 17 mpg my norm is between 15.5 and 16.75 depending on what I did that week . Last week I got 15.89 mpg but I had a dodge dually that ............. just had to be taught a lesson }>. The driveablity is still great I have a 6 speed with 4:10 gears and can cruise along in OD at 30 mph in traffic no problem, no hopping and skipping . I still think it to be a worth the effort mod.
Attachment 47163