92 Ford Mustang GT, Keyless Entry Installation Trouble

Here is a DEI document that explains the common vehicle door lock systems : https://www.the12volt.com/installbay/file.asp?ID=708 The Mustang is a 2 door, so a 15 Amp fuse should be all you need. Your circuit understanding is correct. The added relays will allow the door locks to work normally. The ford door switch signals go through them as if they weren't there. But the relays opens the circuit to apply the +12V motor current to only the open or close side of the lock motor when the aftermarket system is operated.Soldering is fun!

I got the new switch in. Once installed the locks function normally. I've been busy with family and sick, so I haven't had an opportunity to work on the relay system.

Got it all going. I had the wires swapped going to the switch and the motor. Installed a fuse and swapped them around and now it is working like its supposed to. Thanks again for all the help! Maybe someone will read this and learn from my mistakes.

One more question. The unit I have will also pop the trunk. I'm in the process of trying to get that hooked up. The wiring instructions indicate that the unit sends a negative trigger signal. I wired the relay so that I have a constant hot on the relay and the trigger signal coming into the other side. At this point I'm just trying to fire the relay. I got everything hooked up and when the key fob was triggered nothing happened. Using a multimeter set to continuity I started checking things out. With one side of the meter connected to a chassis ground I put the other end on one of the negative door lock trigger wires. When actuated with the key fob continuity will briefly go from 1 to 0. When I do the same with the trunk trigger the continuity instantly drops to below .6. When I trigger the key fob the continuity moves a little but does not go to 0. I switched the meter from continuity to voltage and tried the same exercise to make sure that I'm not getting a positive trigger. No voltage. Am I doing something wrong or do you think the cheap keyless entry I bought is broken?

The correct way to use a DMM to check for a (-) output signal is like this ; DMM set to 20 V DC. Red test lead to (+) 12 volt constant. Black test lead to the RKE Trunk output wire. When the RKE unit outputs the trunk release signal, typically 1.0 second long, the DMM will go from 0v to +12 volts.Soldering is fun!

Kreg, Thanks for the reply. Last night when I was testing I also did what you suggested and I was not able to read voltage. When I trigger the RKE to open the trunk you can hear the relay in the box actuate, but it doesn't seem to be sending a signal. The RKE was $18 on Amazon. I think I'm going to exchange it. Using the test method I described in my other post I was able to verify continuity triggering the lock/unlock relays. Also when I put DMM on the lock/unlock leads it stays at 1 until you hit the relay then it drops to 0 for a split second. When I do the same thing with the trunk unlock wire it immediately drops to 0.56 and stays there. Any idea why it would do that?

Not sure on that. I don't use continuity to test the controllers outputs. Are the lock and unlock wires connected to the car during this continuity test? Is the Truck Release wires connected to anything during this test? That could explain the difference. Bottom line, connect the Truck output to a standard 30/40 amp SPDT relay like this : +12V constant to Pin 86 RKE (-) Trunk Release output to Pin 85 Make the RKE do a trunk release with its' remote. You should hear/feel the relay click/energize for a second. You could even use your DMM continuity test with pins 87 to 30 to verify.Soldering is fun!

Yes, the lock and unlock wires are connected. I'm using an alligator clip connected to the DMM and the negative trigger wire of the RKE. The other lead on the DMM is going to chassis ground on the car. The theory is that if the RKE internal relay is functioning normally and sending a negative trigger when I trigger it with the key fob the relay will close and complete the continuity circuit. This test worked for the lock/unlock relays. When I do this with the trunk wire I get the odd readings. I wired the relay in as you described. Because the RKE relay tends to make a lot of noise I held the trunk popper relay in my hand and triggered the RKE. It doesn't do anything. Just to make sure that I had a good relay I grabbed a new one out of the box, I ordered 5, and tried it. Again nothing. Taking it one step forward I got a few scraps of wire together and wired one of the relays so that it was getting constant 12volts then using another wire I tapped it to ground. The relay fired as expected. This all leads me to believe that my RKE is not functioning properly. Early in this adventure of keyless entry and trunk popping I wired the door lock actuators wrong and could have send a voltage spike through the RKE control box.    I'm the one asking for help here so again thank-you for you interest in helping and the responses. This is not my strong suit and understand that I could be completely wrong about all of this! Thanks again, Nick

Your testing is good. It would appear that the (-) Trunk Release Output is no good. Does the RKE system have an AUX output or a Second Unlock output?Soldering is fun!

Not one that would be convenient. The key fob only has lock, unlock, and a trunk button. I went ahead and ordered a replacement. Thanks for the help!