Introduction: 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. 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.
Necessary tools:
- a 15-30 watt soldering iron (or 600F - 700F)
- a Rosin core solder (Rosin is less corrosive) and
a solder wick (copper braid) (wicks/braids are bit tedious and usually wasteful on large jobs, but the wick is a good choice for this project.) or - a Desoldering pump (usually requires many attempts) or
- a Desoldering iron (simple to use, How to use, see step 1.)
STEP 1.
Stick a small flat head screw driver in between the wall flap (a clip) and the relay base.
Do not go in too deep. Pry it open just slightly.
While holding it still, use the same screw driver, pry the other side.
While holding this side still (and cleared of the locking edge) pull the relay straight out, or forward.
Installation is reverse of the procedure (Note: The main relay will only go in one way into the housing.)
Note: Do not stick the screw driver too deep inside. You may damage the relay’s mechanical or electrical parts.
Desolder the inadequate terminal and the faulty terminal.
1.)Press and hold the air vacuum bulb. Apply the desoldering iron tip so that the terminal penetrates within its orifice.
2.) When the solder liquefies, start gently to rotate the desoldering tip so that the component’s terminal can be eased away from the sides.
3.) Release the air vacuum bulb just long enough to suck the solder.
Note: If any solder remains are left on any terminal after attempting to desolder it, resolder it with fresh solder and repeat the desoldering process.
STEP 2.
Heat the terminal and the copper trace with the iron tip while applying the rosin core solder to the terminal.
If you do have a joint which looks in need of rework don’t be tempted to just reapply the iron. This is unlikely to succeed as the solder in place will have no flux in it, so the flow across the joint will be worse than when it was first made. Better to remove the solder, using a desoldering pump or copper braid, and make the joint again. The flux’s job is to strip away all of the grease from the surfaces to be soldered, thus ensuring that the solder will flow properly. A concave should be formed with an angle of 40 and 70° from the horizontal.
STEP 3.
(Optional) Clean with steel wool, inspect for imperfections then use a conformal coating material. Conformal coating enhances performance, improves electrical stability as well as accidental shorts and thermal shock. Their ingredients include varnish, epoxy, parylene, polyurethane, silicone, acrylics, or lacquer. Coatings are applied in a liquid form; when dry, they exhibit characteristics that improve reliability. These characteristics are:
Heat conductivity to carry heat away from components
Hardness and strength to support and protect components
Electrical insulation to preventing accidental shorts
Low moisture absorption
Prevents oxidation * tip: If your Honda digital clock currently works, now is a good time to protect it with conformal coating.
To remove the conformal coatings simply use acetone.
STEP 4.
Install onto the vehicle in a lower, practical location*, easily accessible in the future. Your work is done.
Hope this helps anyone with a faulty main relay. Instead of spending $50 bucks for a new one, just fix the one you have.