Headlights randomly shutting off again, I think the turn signal box is the culprit?

[neonshaun]

A while ago I had an issue where all my lights shut off mid drive. After letting it sit for a while, the lights turned back on and it was fine.
I replaced the headlight relay and thought... that's that.

But I was driving to work the other day and noticed my turn signals wouldn't cancel. Thought "hey! I bet my lights won't turn on now!"
And I was right, they didn't, until I smacked the steering column a few times.

I thought the switch was bad and I'd have to shell out $1k for a new one, but it looks like it might be the turn signal box?
Does that make any sense? I've made a video here:

https://www.youtube.com/watch?v=0f7o4Y77heo

 

[Old Guy]

I thought the switch was bad and I'd have to shell out $1k for a new one, but it looks like it might be the turn signal box?
Does that make any sense? I've made a video here:

Maybe!

The wiring diagram is a bit confusing. The diagram indicates that the headlight control switch that controls the headlight relay gets it ground connection via the turn signal control unit. However, the diagram implies that the turn signal control unit does not have any role in the headlight switch operation. It looks like the ground connection for the headlight switch just goes to the turn signal control unit to share a common ground to the chassis. If that common ground fails then both the headlights and the turn signal unit will likely cease operation. I would start by getting the service manual with the pin outs for the turn signal control unit plugs and check the status of that ground connection.

Based upon your intermittent operation there could be an internal connection problem in the turn signal unit associated with that ground pass-through or there could be a bad connection on one of the plugs.

 

[JohnWayne]

I think it is your turn signal switch. Had same problem on one of my cars and replaced the switch and it fixed it. You can try to clean it first to see if that will help

 

[neonshaun]

I think it is your turn signal switch. Had same problem on one of my cars and replaced the switch and it fixed it. You can try to clean it first to see if that will help

By switch, do you mean the entire stalk unit (~$1000) or the box that controls the turn signal on top of the steering column (~$300)

 

[JohnWayne]

By switch, do you mean the entire stalk unit (~$1000) or the box that controls the turn signal on top of the steering column (~$300)

Control box on top of column

 

[neonshaun]

cool, ordered a new one. Last night I noticed that even when the plug is in the turn signal control box, the lights will occasionally fail to turn on until I tap on the turn signal box.

After taking it apart, it looks pretty crusty in there. A lot of the solder is covered in corrosion, I'm assuming some of the capacitors have started to fail, and this is a box that it well shielded from sun, dust, and moisture.
Worrisome that it pretty much hit the same fate as the CCU. What other common components will start failing due to bad caps? Supply for these parts is going to run thin.... I'm scared.... hold me sweet baby nsx.....

 

[Old Guy]

Did you check to make sure that your ground connection is OK? Because of the pass-through nature of the ground, failed capacitors in the control unit should not affect the headlights. However, failed solder joints in the control unit because of corrosion could result in grounding problems for both units. Or, as is common with the main FI relay, the solder connection for the ground terminal (and others) may have developed a fracture resulting in flakey operation. I seem to recall a thread that is about one year old or more that addressed the problem of failed solder joints in the fan control unit causing problems. Reflowing of the solder joints fixed that as I recall.

The turn signal unit probably gets as much or more exposure to heat than the CCU and head unit. As such, it is not a particular surprise that it would suffer the same type of capacitor failures. Did you give any consideration to experimenting with capacitor replacement? If you have a new one on the way, perhaps see if doing a capacitor replacement and check for fractured solder joints fixes the problem. Perhaps the problem of premature cancellation that seems to afflict a lot of NSXs is related to capacitor deterioration.

There are a pile of little boxes on the NSX that are filled with electronics. For those boxes that use electrolytic capacitors, its reasonable to assume that they are probably all going to suffer the capacitor dilemma. I recall a comment in a classic car magazine that failed electronics were probably going to be the Achilles heel for people interested in restoring late '80s through '90s vehicles. Probably time to develop some soldering skills or get Brian K's telephone number into your phone book list.

 

[neonshaun]

I tried directly grounding the black wire to/from the turn signal box... but that didn't make any difference.
I'm going to try reflowing the circuit board tonight, since it will be ~1.5 weeks until the part is shipped to me since they have to order it.
I don't know enough about electronics to start diagnosing caps... what do you do, just short em out and see if they explode? :biggrin:

 

[Old Guy]

I don't know enough about electronics to start diagnosing caps... what do you do, just short em out and see if they explode? :biggrin:

That is not an effective way to get them to go poof. There are other means if you need some drama.

In the case of the NSX electronics, there is not much to diagnose with the electrolytic capacitors. The typical tell tale signs are that the seal on the bottom of the container has failed (the connecting wires go through the seal on the bottom) allowing the electrolyte to leak out. The electrolyte is corrosive and can damage the traces on the circuit board in which case you are in to more than just replacing the caps. The other signs are that the sides of the capacitor can are bulged and if there has been an internal short the burst disc on the top of the capacitor may be ruptured open - again allowing the guts to ooze out on to the circuit board.

In the last year there have been a number of threads covering the replacement of the capacitors in the head unit, door and sub woofer amps ( [MENTION=18814]crxguy52[/MENTION] and others), in the SRS unit and in other modules. If you go back a number of years you will find threads on the CCU capacitor replacement. The posts have pictures of typical dead capacitors and discuss the replacement.

 

[neonshaun]

whelp, i'd say that officially fixed it.

I replaced the turn signal box, and have been switching my lights on and off rapidly all week and it's never failed.
I put the old box back in and switched them on and off and it failed after ~4 switches.
If anyone wants the old busted box to test with, LMK.