Fixed my PGMFI main relay!!!!

Engine would sometimes stop for no reason, and would not trigger any codes so I figured it would be the main relay. Today, I could not even start the car so I held it cranking and tapped the relay box with my finger then it started.
I pulled the cover off the box and found that flexing the board with my hand would make the relay work. I could also feel some of the solder joints mooving and when I looked at the back of the board I noticed that some of the solder joints had cracked. It is quite hard to see the cracks, but I re soldered them and everything works fine!!!

I think the vibration from the relays opening and closing must eventually weaken the solder joints.

Anyway, a nice easy DIY for most of you guys if you suffer the same problem.

Well done. This is what usually kills the relay, and also why it's intermitant. 2 minutes with a soldering iron and they are generally good as new.

It is supprising how much smoother the car feels now. I had noticed a slight hesitation every now and then, but it seems to have gone away.
Also, I would often feel the engine cut for a second and then get a TCS warning light. I assumed this was a problem with the TCS, but now I am sure the problem was the relay. The lack of signals from the ecu must have triggered the TCS warning.

HYPERTUNE said:

Engine would sometimes stop for no reason, and would not trigger any codes so I figured it would be the main relay. Today, I could not even start the car so I held it cranking and tapped the relay box with my finger then it started.
I pulled the cover off the box and found that flexing the board with my hand would make the relay work. I could also feel some of the solder joints mooving and when I looked at the back of the board I noticed that some of the solder joints had cracked. It is quite hard to see the cracks, but I re soldered them and everything works fine!!!

I think the vibration from the relays opening and closing must eventually weaken the solder joints.

Anyway, a nice easy DIY for most of you guys if you suffer the same problem.

Click to expand...

You made my day :smile:

You're telling exactly what happened to me. After reading I ran to my NSX, pulled out the main relay and saw a cracked solder joint. I soldered it and everything was solved.

Thanx

HYPERTUNE said:

Engine would sometimes stop for no reason, and would not trigger any codes so I figured it would be the main relay. Today, I could not even start the car so I held it cranking and tapped the relay box with my finger then it started.
I pulled the cover off the box and found that flexing the board with my hand would make the relay work. I could also feel some of the solder joints mooving and when I looked at the back of the board I noticed that some of the solder joints had cracked. It is quite hard to see the cracks, but I re soldered them and everything works fine!!!

I think the vibration from the relays opening and closing must eventually weaken the solder joints.

Anyway, a nice easy DIY for most of you guys if you suffer the same problem.

Click to expand...

Yeap i was having the same problem, and I could tap the relay and it would final start. The relay wouldnt fail for about 4 starts, and then DEAD again. I took it apart and redid all the joints, and it hasnt failed since.

I have no current problems, but with all the recent posts regarding this I decided prevention easier than cure! It took me all of 10 mins total start to finish (tip: plug in the iron before you remove the relay!)

1) Plug in soldering Iron
2) Remove rear-upper trim panel
3) Remove Relay - 0ne 10mm bolt & unplug two connectors
4) Pop off the cover
5) Re-solder each of the pins on the base of the board
6) Reverse above process - except don't de-solder the pins when reversing step 5! <!--StartFragment -->

http://www.nsxprime.com/photopost/data/500/5957rear_interior.JPG

D'Ecosse said:

I have no current problems, but with all the recent posts regarding this I decided prevention easier than cure! It took me all of 10 mins total start to finish (tip: plug in the iron before you remove the relay!)

1) Plug in soldering Iron
2) Remove rear-upper trim panel
3) Remove Relay - 0ne 10mm bolt & unplug two connectors
4) Pop off the cover
5) Re-solder each of the pins on the base of the board
6) Reverse above process - except don't de-solder the pins when reversing step 5! <!--StartFragment -->

http://www.nsxprime.com/photopost/data/500/5957rear_interior.JPG

Click to expand...

does the rear upper trim panel just pop off? Is that the one piece that need to come off?

Thanks.

nis350 said:

does the rear upper trim panel just pop off? Is that the one piece that need to come off?

Thanks.

Click to expand...

Yes, just the upper panel that runs along under the window - pop it out towards you at the top edge to unsnap the button clips (one each, left right & centre). then lift up to unhook the metal clips at bottom (not really a clip, just a stay)

nsxprime rocks....

For the last 6 months I have had an intermittent problem where as the car was almost done warming up, the engine would die for about half a second. It would not happen every time I drove the car, and would only happen once if it did at all (usually under acceleration). The RPM gauge would stop reading and quickly drop to zero, then bounce back up as soon as the engine kicked back in. Other then the engine/rpm gauge the rest of the electrical system appeared to stayed on. Had the shop take a look when I took it in for the 90k service and they could not figure out what the problem was. The started guessing fuel pump, coils, ignition...


Before dumping money into random parts I decided to take a peek at prime. Searching through the forums I started running into all the threads discussing the main relay and the wide variety of gremlin electrical issues caused by it's failure. Sure enough after resoldering the components onto the pcb the problem was entirely resolved. One thing I noticed was the the joints were pretty short on solder. They soaked up a fair amount of new solder when I was redoing them.

What an easy(skill, time, hit on the wallet) repair for such a PITA issue....

This topic really interests me because I keep having intermittent problems with this issue.

I've bought and installed a new main relay ($60) and the problem went away. Then it came back so I took it into Honda and they said it was my TCS wiring harness which needs to be replaced ($$$). I disconnected the upper TCS electrical plug in so that my TCS is shut off (now I have the TCS light always on the dash) and that solved the problem for a while. With it still disconnected the problem is back!

How can I solve this to finally put a rest to the issue? Check the new Main Relay again for soldering issues?

Jetpilot

D'Ecosse said:

I have no current problems, but with all the recent posts regarding this I decided prevention easier than cure! It took me all of 10 mins total start to finish (tip: plug in the iron before you remove the relay!)

1) Plug in soldering Iron
2) Remove rear-upper trim panel
3) Remove Relay - 0ne 10mm bolt & unplug two connectors
4) Pop off the cover
5) Re-solder each of the pins on the base of the board
6) Reverse above process - except don't de-solder the pins when reversing step 5! <!--StartFragment -->

http://www.nsxprime.com/photopost/data/500/5957rear_interior.JPG

Click to expand...

Could this also be contributing to my seldom cranking problem but won't start until I take the key out and restart again? Is this one of the early symtoms?

emeraldtt said:

Could this also be contributing to my seldom cranking problem but won't start until I take the key out and restart again? Is this one of the early symtoms?

Click to expand...

My gut feeling would be that this issue is caused by the ignition. However given the number of people reporting issues with the main relay and how badly my unit was soldered I would not consider it a waste of time to fix even if it does not solve your problem. It's a quick and free repair.

-martin

this is very interesting - when starting my car, turn the key and I get maybe a half second delay then the the engine starts. Before it was instant.

Sometimes it doesn't do anything at all. Then I have to turn the key to the off position, then try again and its fine. Very weird! Do you think my main relay is going out? Where is this unit exactly? its inside the car behind the drivers seat? Or what? thanks

Old thread revival, but wanted to thank the OP, mine today, for no apparent reason wouldnt start, so off to Prime. This is the thread that seemed to fit my situation, so I gave it a go, no new solder, just went through and reset each old one, and she starts right up now...

Wish everything was this simple. Thanks!

Don

Thanks for the info - I'm doing mine tomorrow! After reading alot of the DIY posts here, I'm starting to get the feeling my car is gonna break down every time I drive it . Maybe there should be threads stating how long cars have been running with just the manufacturers required maintenance :smile:.

Took mine (1991) out today and found one cracked joint (that I could visibly see only with a magnifier - the cracks seem to be mostly on the rectangular joints holding the relays onto the board). These cars were built with such tight quality controls we may as well figure what happens on one or two will probably happen on all of them. Although my car had no symptoms I'm sure I prevented future problems in the confines and comforts of my own garage. Easy fix - highly recommend you check yours!

Is the main relay problem seen in all years of NSX? I intended to do the solder reflow on my '96 as preventative maintenance.

The diagram in the link listed earlier in this email string shows trim panels that appear to be the same configuration as for my '96. That would seem to indicate Acura moved the relay from earlier years, because on my '96 accessing the relay involves removing not only the upper panel but also the side panel (passenger side).

I notice the part number is 39400-SL0-A01 for a '95 & '96, and 39400-SL0-003 for '94 - '94. Perhaps the -A01 version doesn't have the cracking solder joint problem?

Does anyone have experience with or further info on the two versions of the main relay?

A few months ago my 92 started to show symptoms.

About once in every 20 cold starts, it would lose power for about 1/8th of a second after a minute or two of warm up, then be fine the rest of the day. The engine would stutter, I'd hear a click-click behind me, and the yellow TCS light would come on. After lots of episodes, I noticed that if I turned the key between positions slowly while starting, I could hear a difference in what the relays sounded like on the days when it acted up (kind of sloppy as opposed to crisp).

A few days ago, it wouldn't start, but turning the key all the way off and retrying worked. Then the next day it wouldn't start at all.

Time to search for hints before calling the tow truck! I found this thread and resoldered the relay board. Now all is well. Thank you NSX Prime! (There were two barely visible flaws in the soldering.)

BTW, the connectors on my relay box were behind the center speaker panel, so I had to remove the top, left and right trim, as well as the console storage bin and rear speaker panel; a bit more than 10 minutes. :smile:

The resoldering job was done on my NSX about 7.5 years ago and I have not had any problems since.

I got a PM asking where exactly the relay is.

Here are photos of the appropriate pages in the service manual. The first shows where the relay is, and the second shows the trim pieces you need to remove to get at it. If you're lucky, only one trim piece needs to be removed (labeled 2, Rear Center Trim Panel).

http://www.nsxprime.com/forums/album.php?albumid=402&pictureid=2033
http://www.nsxprime.com/forums/album.php?albumid=402&pictureid=2034

hello, can you say or buy it to me main relay and the n° of main relay for my 1992 NSX? thank you very much:smile:

Thunder said:

hello, can you say or buy it to me main relay and the n° of main relay for my 1992 NSX? thank you very much:smile:

Click to expand...

Not sure what you're asking. Being Canadian, I have a good chance of understanding if you repost in French. :smile:

I just replaced my relay with a new one, although I hadn't had any noticeable symptoms. I figured that since I'm making the long trek to NSXPO this October, I didn't want to be stranded in the middle of nowhere.
BTW what does the letters "PGMFI" stand for? Howard

Oldduffer said:

BTW what does the letters "PGMFI" stand for? Howard

Click to expand...

Programmed Fuel Injection

cmthomson said:

Not sure what you're asking. Being Canadian, I have a good chance of understanding if you repost in French. :smile:

Click to expand...

bonjour, pouvez vous me dire ou puis je acheter le relais principal? j'ai beaucoup de petites pièces a acheter pour ma NSX OEM (boulons, écrous, joints, relais, etc etc...), je ne trouve pas de boutique en ligne qui expédie en Europe, pouvez vous m'aider? je vous remercie beaucoup l'ami! :smile: