ok, so i posted a thread about a week ago about my car dying in traffic and thanks to you guys i found the excellent repair your relay control module joints thread...but after getting the RCM out of the car and looking at specified joints, they look fine to my untrained eye. what should i be looking for? im going to take it to a computer repair shop and have the joints soldered tomorrow but after seeing the joints im a little worried that it isnt going to fix my problem. my car is acting exactly like those who have posted about their RCM's, will die in traffic, or not start, but if i leave it sitting for a while it will start right up. all electronics work when key is turned, just doesnt crank, or even try to...no "clicking" noise or anythimg. so, it fits the bill but the joints look fine. is it possible that the problem is still the RCM, im just not able to see it visually by inspected the joints? in the repair thread the joints are visibly damaged. just slightly confused and thought id see if i could get some input from you guys, thanks.

 

it could still be micro cracks or cold solder joints... I resolder ALL the pins on mine to make sure there were no bad joints.... (I tend to go overboard though.... especially when soldering is so easy and your already there with a hot iron and solder in hand)

 

Look VERY closely around the pins on the "Solder Side" of the board. You are looking for any (almost microscopic) gap between the pins and the solder on them.

ALSO, any pin that is completely covered over with solder can be fractured under the solder (I am referring to a pin that is short and doesn't stick up far enough to be above the level of the flowed solder). What this means is that you must flow solder well on any such pin to be sure it has not failed.

 

You have to use a magnifying glass.

 

i do see it! this makes me feel better...its a relief to at least know what the problem is.

i honestly cant thank you guys and this board enough...without this info who knows who much this would have cost me, and im short on cash right now....so, much appreciated.

 

These guys are great. I had the same problem, looked at the solder joints and said they seem fine just like you did, finally got a magnifing glass to take a look, and said the same thing you did. Soldered them up and no problems since.

This forum rocks because of the wonderful people on it. Sometimes the political comments curdle my bone marrow, but hey, I just bite my lip and move along.

Good luck with the RCM.

 

When looking at solder on a circuit board, the other thing that can trick you into thinking things are OKAY, is a COLD SOLDERED JOINT.

A cold joint will manifest itself as being a dull grey in color, versus a nice shiney silver tone.

Easily fixed with a hot iron and dab of new solder.

(This affliction will also haunt poorly conditioned males who have lost their sex drive...LOL...)...

 

It is the temperature of the pin/terminal that determines the strength of the joint. The solder will melt very quickly and the thin layer of copper on the PC board will get hot from the molten solder, but the terminal will take a little more heat.

I think it is best to wick away the existing solder and carefully clean the terminal as it will have corroded where it was not covered with solder. They may not have been clean enough to start with.

With the terminals cleaned use a resin cored solder-not acid cored solder or acid flux- and a nice hot soldering iron. The six joints mentioned in the original thread are the ends of bus bars and are not liable to be damaged from a little extra heat. Use a nice sized soldering iron resting a good area of the the iron against the pin, or the heat applied to the terminal will be carried away faster than you can get enough heat to it and prevent it getting up to the soldering temperature. This may have been the reason they fail.

Solder comes in a variety of alloys, you do not want to use the type you use on your copper plumbing for instance. Using acid flux will give you more headaches down the line. It is acid and eats away at the metal until it is spent or totally removed, OK on big copper pipes but not dainty terminals.

 

well, i probably should have read the above before i took it to have it soldered by a computer repair shop today. hopefully he got the pins hot enough and used the correct solder...either way, car started right up. that doesnt mean all that much since it would start before but i feel pretty confident that my problem is fixed.

i looked at the joints through his magnifying glass and the middle joint had a hairline crack all around the pin, the left joint was very dull gray as described above, and the right joint had a small hairline crack....not sure how i thought they looked ok upon first inspection lol.

again, thanks guys.

 

Well, I didn't need one until about the past 5 years.

 

If the shop you took it too is half way decent they probably did a fine job on the re-soldering..... it is not that difficult. Controlling an automated PCBA process is much harder than hand soldering these things.... that is why we see these problems....

 

It's all downhill after 50.