Well I've made some progress. First, I cleaned out the drains below the hood hinges. They were well clogged and, based on some other info from this forum, this can lead to water in the interior. I did find some water under the fron passenger floor mat. Since it's winter in Seattle I've already have several chances to test it and so far it looks like it's staying dry.

Second, I now have my central locking working as it did before. The problem was bad connections in the channel under the rear passenger side carpeting. There are three splices that impact the central locking. I cut off the splices, stripped the wires and twisted them back together and it worked. I'll need to make a better connection before I put everything back together.

I do appear to have some problems though. Ever since I bought the car I have only been able to lock and unlock all doors from the driver's door. Locking or unlocking passenger side door or the tailgate had no effect. In looking at the wiring diagram and poking around I appear have two problems.

The ground "supply" for the passenger side and tailgate actuator switches is suppose to be supplied by S8/2, the warning buzzer switch. This switch does not seem to be working or the ground side of the switch is not connected. I have not started trying to track down the connection for this. Apparently the switch is on the ignition switch and the connections are under the drivers side left kick (X30).

The other problem is that there appears to be a short in the passenger side actuator switch. The brown/black wires connecting the locke side of the passenger side and tailgate actuator switches and ground supply wire (from the warning buzzer switch) is sitting at about 7 volts when the passenger side lock is in the locked possition. If I disconnect the tailgate and ground supply wire, the wire from the passenger side actuator switch is still at 7 volts. If I move the passenger lock to the open position, the voltage on the brown/black wire goes away and the signal wire from the actuator is at 12V, as it should be.

BTW I connected the brown/black wire from tailgate actuator switch directly to ground (which is how it was connected beginning in 1990 I guess) and it works fine. I can lock and unlock all the doors from the tailgate.

So, I this point I think I'll just wire it back up so that the tailgate switch works. I don't know how hard or expensive it is to replace the actuator in the passenger door but I sure do hate taking those inside door panels off. Not much point in trying to get the warning buzzer switch working until I can get the actuator fixed.

Thanks again to pesuazo for pointing me to that wire channel under the carpet.

Any other suggestions or comments welcome.

BoB

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1988 300TE
1991 Miata