Main Relay Repair

I started having the classic symptoms for main relay failure. The engine would fire up when I turned the key, but would stop after a few seconds. After three or so attempts the engine would keep running and then I would be able to drive it. On one occasion I got clickey noises from over my shoulder. I drove it three or four times like this before the penny dropped what was going on and I remembered reading about this problem on the forum. Luckily it didn't let me down but I decided to put my spare new main relay in. I followed the excellent step by step described by Kaz http://www.nsxcb.co.uk/showthread.ph...6800#post66800 which he posted in 2010. It now starts like it always did, first turn of the key. Problem solved.

This relay was the original 1996 one which was resoldered in Feb 2018 as a preventive measure, so it's a reminder to carry a spare.

So thanks to Kaz for his helpful post and thanks to the forum for providing the resource which allowed me to find the information I needed.

But it leaves me feeling a little uncertain about the future. As our NSXs age, more things go wrong and parts availability gets worse, we will need to continue to share our experiences. And yet this kind of sharing is diminishing on the forum. As far as I can see, Faceache is no substitute. Pity.

Peter

Interesting that the re-soldered one only survived for about 3 years although if it was the original one from 96, the parts lasted for 25 years and whatever the mileage covered.

I opened several used main relay years ago and cut through the relay housing to inspect the contacts.

All of them showed fairly clean status but because it was long time ago, I think none of them covered as much mileage or age as yours.

Interesting to see the cause of your failure as it's very unlikely to be caused by the soldering crack.


With the EPS controller, the contacts of the power relay were either burnt or melted due to lack of contact capacity triggering the famous EPS error code #22.

If your main relay failed with the relay contact issue, could be the first one in UK so would be nice if you can keep it for further investigation.

If you are happy, will appreciate if you can forward it to me when we meet next time at the future event, etc.


Regarding the parts, as some of the parts price went up more than 3 times in April, I think we are fine for the foreseeable future.

Some manufactures had to create new mandrel/die and with very limited demand, inevitably, the price had to go up.

I would say we were fortunate until now because although the parts price went up every year, it was only like by few %.

This was the first time it went up massively since the NSX production stopped after 2005 so if you look at it from the different point of view,
it's the good sign that the parts manufactures are still committed to produce the parts, at least for the ones that had the new price tags.

Of course there are already several discontinued parts so if it's known to fail, we just need to take action at the right timing to repair/replace them as the preventative measure.


Kaz

I still trust Honda to supply the parts needed to keep the car on the road as long as the price is right for them. But not so sure about the 'nice to have' parts like Type S or R.

Actually, I was thinking more about the sharing of experiences about how to fix the cars when they go wrong than just the parts availability. As well as my experience with the main relay, I was thinking about when my starter motor failed. I could have just bought myself a new one, but instead was able to learn from Jonathan's post about how he replaced the copper contacts in his starter relay for ~£25, and consequently saved myself some money. My post about the success I had with Kaz's post helps to keep this knowledge current. Facebook is searchable, but it doesn't seem to encourage this kind of sharing. Or maybe I'm not slick enough with Facebook :).

I post up what I can here to help the NSX community as a whole, some things I post on farcebook, but usually when I haven't found a solution and just need a whinge, when I do get a result it gets put here as its better as a reference source..... :-)

I changed my main relay out today using Kaz’s procedure - took me quite a while, mainly because my (DBW) car has a wiring harness in front of the two relay connectors which made it awkward to undo the connectors to get the old one out, as i have big hands. The carbon kevlar seats also don’t go forward far enough for an oaf like me to get in there. It would have been easier with the seats out, but I didn’t feel confident enough to take that extra step.
I’ll aslk a friend who is a University Electronics technician to inspect the soldering on the old relay, and reflow if necessary.
The top trim piece isn’t perfectly in place, but it’ll do for now. If it starts squeaking I’ll have another go at it!
Thanks once again to Kaz, britlude and other forum members who help us inexperienced owners out - it really is appreciated.

The main EFI relay on my 2000 died and stayed dead without prior warning signs back in 2021. Fortunately, it had the good graces to do this while parked in front of our house. I had a spare in the trunk so 30 minutes of messing around with the interior trim panels and I was on my way. I did manage to snap a retainer on the top panel which required an order from Amayama.

The failure points on the relay were the heavy current carrying solder joints where the actual relays are attached to the circuit board. This is a photo showing a failed solder joint on a relay

Attachment 14733

The rectangular pin is one of the heavy current carrying pins on the relay. You can see the failure point around the periphery of the pin. The pin on the right is one of the relay coils and shows what a good solder connection looks like. The failure does not look like a simple vibration related fracture, although vibration may help it along. I expect that the damage is due to heating and migration of the solder around the pin.

This photo shows the location of the two relays on the board (circled areas) after removal of the conformal coating and partial solder removal prior to repair. The area circled in blue is the pin in the close up photo.

Attachment 14734

None of the solder joints along the left side where the sockets attach to the board showed any signs of solder fractures. That is where I expected the failure to be located. What is particularly interesting is that the failed solder connection on the relay in the close up photo is connected via the PCB trace directly to one of the pins on the socket connection. Both solder connections are carrying the same current. The surface area of the solder joint at the socket connection actually looks smaller than the relay connection; but, shows no apparent signs of damage. This suggests that the failure problem is not a design current density problem; but, perhaps the way that the relay is soldered into the board. Perhaps in the wave soldering process the large metal parts of the relay did not heat up quickly enough which resulted in a poor quality solder joint.

The repaired board is now tucked back into my spare parts box to cover for failure of the replacement relay.