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Does the light go out when you close the fridge door? (trunk-open indicator staying on)

11 January 2021
Ontario, Canada
Search turned up empty. After the trunk upholstery was out (related? not?) for rewiring my LED tail lights, problems with the gauge cluster trunk-open indicator and the alarm system:
  1. The trunk-open dash indicator comes on for the initial test but then stays lit whether the trunk is closed or not.
  2. The alarm will not activate.
  3. Trunk light illuminates, so the trunk light fuse is OK.
  4. Test: trunk latch sensor unplugged at C559. Trunk-open indicator extinguishes and the alarm arms normally.
  5. Since the dash indicator (green/black wire?) and the alarm (white wire?) circuits are both not working, the common element is the sensor in the door latch, which should "close" when the trunk is unlatched.
  6. The trunk latch sensor is correctly "closed" when the trunk is open. Latching with a screwdriver, the electrical contacts do not "open". (I was afraid to lock myself in the trunk even with the emergency escape latch inside.)
  7. Suspecting the trunk latch sensor is stuck electrically "closed", indicating the trunk is open when it's not, I took a video from the inside of the trunk. Video: The trunk light does not go out when the trunk is securely latched - the switch is not "opening" when the trunk closes.
  8. (The trunk latch works fine mechanically, latching the trunk securely and unlocking with the key.)
The OEMAcura parts diagram suggests the sensor switch is not available separately. Part #: 74850-SL0-013
Anyone else had this problem or otherwise changed the trunk latch or trunk latch sensor? Or any other ideas on something else that might be wrong before I order a new trunk latch?
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The trunk latch switch is a microswitch that is riveted on. I would discon the 3P connector, use some long thin wire, connect them to the terminals on the main harness, and manually duplicate the open/close cycle of the switch with the wires outside the trunk.

No need to replace the whole trunk lock, as the switch is a microswitch. Though it appears to be a somewhat non-standard microswitch form factor. Microswitches are pennies to buy and they can be serviced, replaced, or rebuilt. A cleaning might work or you might have to rob from other similar switches.

If the switch IS testing bad: I would dismount the latch, drill out the retaining rivet, and open up the switch body. Do this on a large light color towel or cloth so you can find the small pieces as they go flying out while they make their escape. Scalpel and curette type tools helpful.

I advise becoming a YouTube Certified Expert in microswitches.

Then replace the drilled rivet with a thin truss/round head bolt with a nyloc, mount back on lock assembly, and then installation is the reverse of the removal process :)

C8E-G38H is the number on the switch, but detailed photos of the switch would be helpful.

What is amazing is that Google picked up the switch number from an image on an eBay listing.
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Thanks for the precise answer on switch replacement @drew ! That said, the whole latch is only $66 added to my yearly amayama order so it may not be worth searching for a switch. I'm mostly worried that it's something else that I haven't thought of.

No need to test with small wires - my video clearly shows that the switch is not "opening" when the trunk closes.

(2001) C559 is a 3-pin connector, not 2, which closes a green/black and a white both to ground (black). Grounding the green/black completes the circuit for the trunk light and also feeds back to the dash for the trunk-open indicator. The white goes to the alarm, presumably to sound if the trunk is opened, and also prevents the alarm from arming if the trunk is open. Based on the electrical manual wiring diagram, it should be a double pole, single throw switch. I'll see if I can find it independently.

Correction: 2001 Electrical Manual wiring diagram is different from my 2001 NSX. The green/black and white wires both change to a blue/green union after connector C559; it is just a single pole switch.
PXL_20231201_041041505 (1)-min.jpg
I'll give it a go when the snow flies - should be a few weeks.
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Latch removed. Microswitch stuck "closed". Reads Omron Japan, 2250RC C8E-G38H. Search unsuccessful. It is sealed with epoxy - I don't think I'm taking it apart/fixing it.
Anyone recognise this as a switch from something else that can be ordered? Otherwise, I have a microswitch from another project so I may try drilling new holes in the latch to mount that instead. It's not waterproof like the OEM, but there doesn't seem to be moisture getting in there. There's not even any dust in the grease after 22 years!
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That IP67 does look close, but the pin & hole are reversed. Agree I could probably make it work, but since it will be a bit of bodging anyway, I decided to bodge one I had lying around.

After removing the old switch with a side cutter and twisting out the mounting pin rivet, I used the original holes to mount a generic microswitch. The microswitch holes were too small for zip ties on hand, so I sewed it in with upholstery thread through one of the holes and around the end.
PXL_20231202_021103867 (1)-min.jpg
Removed the unneeded terminal, crimped on a couple of female spades and done. Label: 5A 125 250 V - 10285? 5A is ++ for a trunk light.

New trunk video confirms correct trunk light operation, trunk light indicator on the dash is working, & the alarm arms normally. :)

Final verdict:
Don't do this. Just spend $186 for a new latch at your local Acura dealership, or much less if you were already going to put in an order of other parts. But I enjoyed the challenge, & there's 1 less latch in a landfill.
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I meant "IP67" which is a water resistance rating.

I would use some hot glue to lock it down and seal up the switch connections.

A small thin pan head bolt should work well enough.

You'll probably have to redo this once a better switch is found...
That works. Personally, I would have been inclined to use two 4-40 or 2-56 machine screw / lock washer / nut s to hold it in place rather than exercise my weaving skills :).

The switch does double duty for the security system so you want to make sure that you have a good quality switch so that you don't end up getting flakey operation from the security system a couple of years down the road. IP 67 would definitely be a desirable qualification for the switch, primarily the 6 part of the 67 which indicates dust resistance.
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Appreciate the feedback guys, good advice.

That upholstery thread with 12 turns will have a yield strength of 1200 lbs, which should hold a microswitch. I contemplated using Dyneema (UHMWPE) with strength >200 lbs per fibre, but it is difficult to stick-tie under significant tension. I may be more comfortable sewing since I usually sew more valuable things than NSX's (I've also got sports equipment I've repaired with upholstery thread that's older than my 2001 NSX & the dust seals I sewed on my Wrangler axles are still holding after a decade.)

I was satisfied with this switch because I could find no evidence of water or dust ingress into this space over the last 22 years. Commercial plastic terminal covers were OK because neither of these wires carries significant voltage or current potential. One wire is a ground, so doesn't even need insulation in theory. The other connects to the ground side of the trunk light, so if it shorts out, all it will do is trip my trunk light indicator like my blown OEM switch did. Compromise of the switch or either wire will be apparent with either no trunk light or +ve trunk-open indicator, with little additional compromise.

So I've changed my final verdict to:
Don't do this. Spend $186 for a new latch at your local Acura dealership, or much less if you were already going to order other parts. While I enjoyed the challenge, & there's 1 less latch in a landfill, I'm not sure how long I'll be able to go without replacing it with the OEM part as I'm so anal about the car. I lasted a year with my upholstery thread repair to a broken targa handle which was stronger than OEM, but I couldn't help myself from later replacing it with an OEM one anyway.
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Don't throw it away. Save it in a parts box because in 5 - 10 years the latch may be out of production and somebody else may need it. If the home stitching bugs them they can substitute a couple of 4-40 machine screws to make it look more factory like.