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Info about venting the main relay casing (« z00m z00m »)

3K views 7 replies 4 participants last post by  z00m 
#1 ·
Zoom, Zoom,

See below (the last paragraph) for the info I promised to post for you on venting the main relay. See http://techauto.tripod.com/mainrelaysolder.htm for the actual pictures that come along with the text.

I went down the path of venting after I began experiencing the no-start when hot problem AND decided that fixing the solder joints was beyond my capabilities. I ran across the info below and latched on to the portion that I knew was within my capabilities -- i.e., drilling holes in a plasting casing. I drilled about four or so holes, and the no-start when hot problem has not re-appeared.

However, I am not qualified to say whether this venting fix is viable or smart to do. For me, it was simple, I had my drill handy, and it allowed me to avoid replacing the main relay. (I, by the way, did not do anything to the solder joints.)

Hope this helps. Best of luck with your auto.

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Honda Accord Main Relay
How to repair the Main Relay.

Figure 1.0

The relay's solder joints crack and separate itself through time and exposure to heat generated by the relay. One of the relay's heat problem is generated heavily by the power consumption from the fuel pump. The best method to repair the main relay is to apply heat and solder to one every part of the joint, especially the part that is associated with the relays. It is advisable to heat a joint with a soldering tip first while supplying solders last. Here's an example. It may even be preferable to remove the old solder and remove the circuit board and recondition the contacts. This should not be attempted with improper equipment as the board will collapse under heat.

How to pry open a main relay:

Stick a small flat head screw driver inside between the wall flap and the relay base, (where a locking edge is at)
Pry it open just slightly
While holding it still, use the same screw driver, pry the other side.
While holding it still (and cleared of the locking edge) pull the relay straight out, or forward.
Pictured below shows that heat may affect the factory prepaired solder joints.

Figure 1.1 This picture shows how several holes may be drilled on the side of the case to vent the flow of heat and allow allow the relay to run cooler. One person have suggested that holes will not affect the relay after new solder application. "The problem lies in the bad solder application by the relay maker [Mitsuba]. Once the the solder joints have been properly repaired the relay should last the life of the car," he mentioned.

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#2 ·
thx :) i've already repaired my main relay twice this summer w/ solder iron but i got it pretty good this time.. i'm still feeling a little unsure because it doesn't really seem to matter when the car gets like 1000 degrees inside heh, still cracks. but i'll definitely do that if i have any more troubles anytime soon

thanks for the helpful linkage, party on
 
#3 ·
welps looks like i'll be doing this friday night or sometime :-/ glad i found out about it, thx for all the links and stuff

i got in the car and it wouldn't turn over and then i turned it again real quick and it made a squeel noise :-/ then it started right up. embarrassing mostly but not really a bad problem (yet). i never did repair the whole main relay cause we have a solder gun rated at like 115 watts, not any 15-30 watt iron to use so i only did that one cracked joint. i believe it may have cracked so soon because when i did it the best i could do was making it kind of wide compared to what it looked like before i did it. that probably made it crack sooner on the inside.. bah.. well so urs is fine even though u have a dry joint since u vented it?
 
#4 ·
I experienced that non-start while hot problem several times. I, then, inspected the solder joints and could not for the life of me find any particular joint that looked bad. I also realized during the solder inspection that I really had no business fussing with the joints anyway -- given I do not own a solder iron and do not have much experience with the topic.

I, then, just drilled 4-6 holes (don't recall how many) and reinstalled. I have not had a problem since then.

I believe it is thought that the joints work fine when the temperatures are relatively lower, but begin to fail when the temperature in the relay casing climbs. Perhaps the venting makes it such that I stay within the joints-work-fine temperature range.

Good luck. (Also, as noted before, I cannot speak to the wisdom and/or risks associated with having vent holes. Please ping other forum members who are better positioned to speak with authority on the topic.)
 
#5 ·
yeah if anyone else knows more about this i'd be interested in hearing whatever you may know.. at first i was thinkin its probably gonna make my car lose power to have a joint that isn't properly soldered that still seems to be working fine, but like u say maybe the joints are all fine and the pcb is just getting too hot. i found another section of that site that told how solders should look and mine wasn't as smooth as the ones on the diagrams so i'm probably gonna touch it up then drill about 5 holes

thx for the info
 
#6 ·
OK here's a lesson on circuit boards. The copper on the board, solder and the part soldered all expand and contract at different rates. Current carrying parts and the circuit trace itself actually heat up. When all these things heat up and cool down many thousands of times, any imperfection will begin to crack and get worse. When it gets worse and seaprate a little, more current has to conduct over a smaller area and it thus heats up more and so on. Sometimes, when it separates a bit you get sparking and then some carbon and oxidation creating more resistance further yet. You cannot detect these cracks when they start by just looking. So heat is a key factor in all of this, the differences in thermal expansion causes separation.

Honda's problem is the fact that the relay supplier used single sided circuit boards without "plated through" holes. Plated through would have created contact area of solder right "through" the circuit board. This is expensive.
The other problem is that if you look at the contruction of the relay board, you will see perforations on the edge. This tells you that they assemble many many of them together, solder them all by dipping in hot solder, and then breaking them off like crackers. This mass dipping is tricky and when you get small parts and large parts together, the large parts run the risk of cold solder joints if it is not dipped long enough. If you dip it in too long, you destroy the small parts. All TVs, Car amps, receivers etc run these risks. That is why whenever you have an intermittent problem, the electronic tech looks and tests the large parts first because the joint is probably the weakest. Also with all the shaking and vibrating it wants to break away first.

Get a good solder joint if you have the solder iron and technique. That's best. If you don't and cooling works, that's fine for now but you are playing with time.
 
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