Targa Top Latch Warning Light and Sensor - Removing Clamshell Engine Cover

I recently removed my clamshell/engine cover/targa top holder. In order to remove the clamshell, I disconnected the harness from both the clamshell and the car behind the coolant reservoir. I now noticed that my latch warning light no longer works on the dash picture of the car. I would like to have the warning lights working as a backup check that the top is latched in properly before driving off.

Can someone explain how to get the targa latch warning lights to work again after removing the clamshell cover? I understand that the sensor is inside the clamshell and senses if the top is stored there or not. I tried plugging just the harness back in and grounding the two wires, one of the wires, and it doesn't seem to work right. I am thinking I need to remove the sensor from the clamshell as well and utilize the sensor somehow and ground the sensor instead?

Side question...does this effect targa owners who substitute NSX-R mesh cover or other engine covers as well? Do those covers have you remove the sensor and harness as part of those modifications? Or do the replacement covers have a spot to relocate the sensor and harness into the new covers to not lose the warning light function?

Not sure which 'latch warning light' you are referring to. I am guessing you are talking about the indicator for the roof lock switch?

With everything in place, the roof holder (clamshell) switch is in the closed position when the roof panel is not in storage. The roof holder switch is in the open position if the roof panel is placed in storage. If you want to trick the safety indicator system into believing that the roof panel is in storage (which I recall then disables the roof lock switches) , just leave the red and blue wires in your photo open. If you want to trick the safety indicator system into believing that the roof panel is not in storage (enables the roof lock switches), then you need to jumper the red and blue wires together. You could also do this as you suggest by removing the roof holder switch and plugging it into the harness.

There is an off chance that when you grounded the two wires to the switch, you might have damaged the safety indicator, although I don't think so. My service manual is in the trunk of my NSX which is in a secure storage facility for the winter - so I am doing this from slightly fuzzy memory!

Old Guy said:

Not sure which 'latch warning light' you are referring to. I am guessing you are talking about the indicator for the roof lock switch?

With everything in place, the roof holder (clamshell) switch is in the closed position when the roof panel is not in storage. The roof holder switch is in the open position if the roof panel is placed in storage. If you want to trick the safety indicator system into believing that the roof panel is in storage (which I recall then disables the roof lock switches) , just leave the red and blue wires in your photo open. If you want to trick the safety indicator system into believing that the roof panel is not in storage (enables the roof lock switches), then you need to jumper the red and blue wires together. You could also do this as you suggest by removing the roof holder switch and plugging it into the harness.

There is an off chance that when you grounded the two wires to the switch, you might have damaged the safety indicator, although I don't think so. My service manual is in the trunk of my NSX which is in a secure storage facility for the winter - so I am doing this from slightly fuzzy memory!

Click to expand...

Thanks for the feedback Old Guy. I was thinking about what you said and jumpered the red/yellow and blue wire together. This dig make the safety indicator light work whenever one of the latches is unlatched on the roof and then when the roof is latched it turns off. Unfortunately, the consequence of doing this is that the safety indicator light stays on the entire time the roof is unlatched or removed. So you will drive around roofless with the warning light on. This is because the roof holder switch has been removed and no longer can open/close the other part of the circuit.

I guess this seems like a small price to have the light on when you drive without the roof, to have the safety reminder to latch your roof properly if you got into the car with the roof in place but not latched. Since it does go off once the roof is back on and latched. So right now I guess I will drive around with it this way and see if it annoys me or not. Should I be concerned with the bulb eventually burning out if you do a lot of open top driving?

I dug around the manual for any info I could find. This is what I turned up. From what I can tell the sensors are basically just doing continuity to ground checks. Depending on what is open/closed on the circuit and you get the safety indicator light or not. But the roof holder switch itself opens/closes the circuit by physically being pushed open/closed when the roof is inserted into the clamshell.

So, I don't see anyway without this physical roof holder switch, to get the safety roof indication light to work as originally designed in conjunction with the roof lock switch.


I contemplated working up a trunk storage solution for the top as opposed to just wrapping it in a blanket and shoving it in. If you had a real top holder solution in the trunk you could wire up a switch to open close if the top was in place. But I have yet to see anyone on prime build a rig to properly hold the top in place in the trunk. Everyone just wraps it and wedges it in and maybe puts bag on top and sides to keep it from sliding.

I dug up some more photos on this to help clarify versus the manual pages and verbal explanation.

Here is the dash light warning for an improperly latched targa top while on the roof. This hopefully prevents you from driving off without properly latching your top and having it blow off while at speed on a highway. It will also stay on until you properly place the top in the clamshell were another sensor makes sure it is stored properly. So the system verifies two locations.

If you elect to remove your clamshell you throw the system out of whack because you are removing one of the sensors in the system which is inside the clamshell. The warning system/light will no longer work properly and will no longer give you a warning of improper latching or storage.

So if you want to trick the system into giving you at least a partial warning, like if you have the top on and you mistakenly don't latch it correctly then this is how you make it work for that situation. It also means that whenever you have the top off you will have a dash targa warning, because by removing clamshell and its sensor the system can't verify the top is stored properly. But you obviously ignore this light as you purposely removed the roof for the time being. However, once you go to put the top back on and properly latch it the dash warning light will go away. I like this because the warning light becomes useful again to warn of a serious situation and if say you let someone borrow your car that isn't used to remembering to latch it they will see a warning light.

If you take the wires directly off the clamshell switch, red/yellow and blue wire, and jumper them you will now have a working dash light for verifying proper latching. If you want to instead remove the harness that feeds the red/yellow and blue wires you can do this as well. Simply pull that harness which will de-clutter the engine bay with one less harness. It plugs into another harness right behind your coolant tank. You can simply jumper the pins on this harness instead and it will be all hidden behind the coolant tank. Much cleaner look.