On Mon, 22 Aug 2011 20:42:34 -0700, Winston
wrote:

micky wrote:
http://www.tegger.com/hondafaq/mainrelayfix/index.html

Next to the fourth picture, it says:

"Removal of old solder As much of the old solder as possible was
removed in preparation for re-soldering. It is possible to simply
re-flow the old solder, but this method is better. "

Does anyone agree with that?

Yes. Re-flowing is *possible* but risky, because
it generally results in a oxide-polluted 'cold' joint.

Finding more webpages on how to fix this car, I came across this,
probably from a different guy:
"It is likely that a layer of hard oxide has built up inside the
solder joint. The layer of hard oxide has to be removed by
desoldering. Other than this, there are no known mechanical problem
with the main relay. "

FTR, this followed "The Honda or Acura turns over but won't start in
hot weather is a symptom of a main relay going bad. This is the result
of the poor solder application from the factory. As a consequence,
raise areas on the joint indicate a "dry joint" which can lead to an
open circuit. The dry, open circuit is the main cause of no start.
This is partly caused by the buildup of heat on the terminals which
expand, contract and subject to vibrations.."

The relay is under the dash, so doesn't get the heat of the engine,
but it seems just the heat of the sun, inside a closed car, then
cooling off every day, thousands of times, causes problems, especially
in the summer. The first guy recommends resoldering this main relay
(fuel injectors and fuel pump) in any car over 8 years old.

The second guy acutally has an enalarged photo of the circuit board
with several joints marked and the symptoms when each is bad, whn you
hold the cursor over the circle! This must be a really common
problem.
http://techauto.tripod.com/mainrelay.htm

And a big tutorial on bad solder joints and resoldering.

But there are wackos who do great detail work too, so I didn't take
his oxide story seriously until you guys confirmed it.

In either event, it is critical to apply separate flux
to the joint to float oxides out during the soldering
process. The improvement in quality is substantial.

I see.

This ia an automotve electical device, a Honda main engine relay and
fuel pump relay, with a resistor and 3 diodes, and has 24 solder spots
on the circuti board. It seems to have a lot of cold solder problems
after a few years.

A 2001 Honda Accord EX, but all Hondas for the last 15 years seem to
use this part.

When you guys resolder, do you just heat it up and add a little more
solder, or do you clean off the old solder and start fresh?

Honestly, I dab flux on the joint and reheat. It is quick
and effective. For joints that appear cold after that operation,
I remove the old solder, re-flux and use good quality leaded
solder. (Then *always* clean with a 50/50 mix of alcohol and naphtha).

Dang. I never clean joints I have soldered. I don't think
anyone ever told me to before.

That hasn't failed yet.

Thrifty guy that I am, it never occurred to me that people would
routinely do the seocnd.

After your first 10 repairs it goes a lot faster.

He calls it dry solder. Maybe that's the automotive term.

He meant to say:
""Cold" solder joints (a frosted appearance),"

Here is a classic example. Note the frosted
appearance of the solder and the lack of 'wetting'
on the pin:
http://upload.wikimedia.org/wikipedi...lder_joint.jpg

--Winston

Thanks, and thanks everyone.