Any Fix to the Early Turn Signal Cancel Function?

[Old Guy]

Dielectric grease is essentially silicon grease and it is an insulator (that is why it is so useful on the rubber boot on the end of COPs). It is definitely not the hot ticket for improving contact operation. I used a proper conducting switch grease when I cleaned up my switch. As I noted in post #5 , I was unsure whether this helped. If Larry B. gets good results with just cleaning and no grease, I would give that a try.

 

[Honcho]

Dielectric grease is essentially silicon grease and it is an insulator (that is why it is so useful on the rubber boot on the end of COPs). It is definitely not the hot ticket for improving contact operation. I used a proper conducting switch grease when I cleaned up my switch. As I noted in post #5 , I was unsure whether this helped. If Larry B. gets good results with just cleaning and no grease, I would give that a try.

That's my plan.

 

[Old Guy]

Perhaps its because the Covid 19 down time is providing more opportunity to dwell on things; but, the left hand early cancellation problem has become a bit of an irritation. I did a test of the cancel switch operation with the car in the garage. According to the service manual, when turning left the cam on the steering shaft is supposed to engage the B switch at 60 deg of steering rotation and the A switch at about 90 deg (according to the diagram). As you further turn the steering wheel to the left B turns off and then A turns off at what looks to be 120 deg of rotation. Only once you have rotated the wheel past 120 deg and then rotate the wheel back to straight causing the cancel switch to go through the B-A sequence in reverse is the turn signal cancelation unit supposed to release the turn signal switch back to neutral. The service manual implies that if you don't rotate the wheel at least 120 deg the turn signal unit should not initiate a cancel if you straighten the wheel.

As if!

I marked the steering wheel rim with masking tape to assist in estimating steering angles. If I engaged the turn signal and turned left about 60 - 70 deg and then turned back straight the turn signal switch would cancel. The SM implies that you need to turn past about 120 deg before you can initiate the switch operation sequence which causes cancellation. I can start the cancellation sequence with a much smaller turn angle. I did the same test when turning to the right and the same problem emerges. I think the problem is that for LHD cars the majority of right hand turns are short radius so the mid turn cancellation problem is less obvious. A lot of left hand turns are large radius with more opportunity for mid turn variation in steering angle which can initiate cancellation. I would expect that RHD NSX owners in GB and the Antipodes probably suffer from premature right hand cancellation.

A number of years ago I did the cancel switch clean and it did not result in any identifiable change in operation of the cancel system. I am beginning to think that the turn angles identified in the service manual may be incorrect and to this end I am wondering if anybody has connected up a multimeter to the cancel switch outputs and watched the outputs while they turned the steering wheel to confirm if the switch operations really do occur at 60 deg and 90 deg. If they operate at significantly less than 60 and 90 deg either the design is not as indicated or there is a wear issue with the cam and switch. Both of these may be hard to fix, in part because the cancel switch (at least on later cars) is only available as part of the combination switch which is north of $1300 US (this problem does not bug me that much).

The other possibility is that the cancellation unit does not work as advertised. The service manual implies that when turning left the A and B switches have t go through the sequence:

A B
0 0 (straight ahead / less than 60 deg rot)
0 X (60 deg rot)
X X (90 deg rot)
X 0
0 0 (120 deg rot)
X 0
X X
0 X (90 deg - this is when cancel occurs)
0 0

On my car it seems like you can initiate cancelation with this sequence
A B
0 0
0 X ( 60 deg rotation)
0 0

I definitely do not have to rotate the steering wheel to 90 before being able to initiate cancellation on returning the wheel. This could be a problem with the AB cancel switch contacts; but, could also be a design change or an ageing problem with the cancel unit. My presumption was that the cancel unit was a series of latches / flip flops and that you had to clock through the complete sequence in order to generate a cancel. This tends to be a binary device rather than an analog device and usually don't have a lot of capacitor issues (basic latches tend to be pure semiconductor devices) and either work or not at all. To this end, I am wondering whether anybody has tested the cancellation unit to confirm that it has to go through the full sequence of AB switch operations to initiate a cancel or whether you can get it to initiate a cancel with some different sequence.

I ask all this because getting access to the turn signal and cancel unit is not technically complex; but, having done this once it is a physical hassle and literal pain in the back for an old guy. I don't want to go there if somebody has done the testing and can advise that I would be wasting time or they already have an answer. The other thing I am mindful of is that on my 2000 the cancel unit is only available as part of the combination switch assembly and if I screw things up this turns into a $1300 experiment.

A final request is does anybody have a questionable or non functioning turn signal cancellation unit that they would be prepared to donate to the cause of trying to figure out the early cancellation problem? I would be prepared to pay for the cost of shipping it to me. If I can get eyes on the inside of a turn signal cancellation unit I might ( or maybe not) be able to figure out what the unit is actually doing or how it fails which might lead to a remedy for the early cancellation problem.

 

[SMYLDOC]

Cleaning those contacts works great for my 92

My 92 with 236,000 miles, left turn signal would not cancel, right turn would cancel prematurely.
Did NOT remove the knee bolster, but followed the above instructions, cleaned the contacts with alcohol, did not re-grease, put back together, worked perfectly
Thank you again Prime for all the help the members provide this community

 

[warrenw]

Drive it like a BMW. No signal lamp required.

 

[dablackgoku1234]

Is there a DIY on which parts to remove and which part to clean?

 

[Old Guy]

I have not seen a complete guide to removal and cleaning of the switch.

Post # 5 in this thread has a picture which shows the contacts in the switch that people are cleaning. The switch assembly is connected to the module that controls turn signal cancellation. Honda refers to the module by the name 'Combination Switch' in the parts diagrams; but, calls it a cancel unit in the service manual. Refer to the electrical section of the service manual for details on how to remove the cancel unit. In order to remove the cancel unit you need to remove the upper and lower steering column covers (page 23-214). Page 23-213 shows the location of the cancel unit. The switch is attached to the cancel unit by a short pigtail of wire. After unscrewing the actual cancel module, as I recall the switch is mounted to the column with a single Phillips style screw. Put a blob of something sticky on the end of your screwdriver (I use butyl sealant) so the screw does not drop down into the steering column assembly while you are removing it. Drop the screw into the steering column and you will be saying f*** - a lot.

R&R of the cancel unit is complicated by the fact that its on top of the steering column. Unless you are outside the car and looking down through the windshield it is really hard to see stuff even with the column tilted down. A small inspection mirror can help spot the mounting screws and position stuff. Before unscrewing the actual switch, take a good look at how it is positioned because during re installation of the switch it is easy to install it without it being correctly seated in its mounting spot with the result that the cancel unit will not function correctly or at all.

The turn signal cancel unit is part number 35285-SL0-A01. It now appears to be unavailable as a single part (even from Amayama) and is only available if you purchase the complete combination switch assembly which is a $2200 (US$ list price) collection of parts. So, be very careful with cleaning the switch because if you bugger up those sliding contacts the repair could be really expensive. You may still be able to find 35285-SL0-A01 from some EBay vendors as new old stock.