92 Ford Mustang GT, Keyless Entry Installation Trouble

Hi, I'm installing keyless entry on a 92 Mustang GT. This seems reasonably straightforward but I'm having issues anyway. This is the wiring diagram for the Mustang door lock circuit. I'm using this wiring diagram from the site as a guide. The kit I bought is a cheap unit made 8n China. This is a pic of the box. I wired the system up and the locks worked using the rocker switches on the doors. When I tried using the keyless entry they made a little noise but didn't work. After a few tries the door rockets wouldn't even work. I took the driver's side door switch out and it appears to have been over loaded. Just for testing purposes I wired post 87 straight to the battery with a 14 gauge wire. Post 85 and 86 are wired with a much smaller wire as they don't really carry a load. Before I hooked up the relays to the car wiring I tested the key fob and the system activated the relays with no issues. Any ideas why this isn't working?

Pic of the keyless entry unit.

Which color wires did you attach to in the Mustang for lock and unlock? Lock should be Pink/Yellow Unlock should be Pink/Light Green Both would be in the driver kick panel. Did you use a fuse when you ran the power to the battery for testing? If not then you probably need to get a replacement door switch before proceeding. Getting everything back to normal will be necessary before troubleshooting further. The unit you are using seems to have onboard relays built in. Is there a particular reason you are using another pair of relays after the keyless module? Figure E could have been used to wire into the locking system from the keyless system. The way you are doing it is fine and will probably be more reliable since the additional relays will be rated higher than the onboard ones. I’m assuming you used the Figure C diagram to provide the negative lock and unlock pulses to your add-on relays? It appears they have a typo in the manual so I marked it up a little to make it clearer. Steve G

I cut into the pink/yellow and pink/light green wires. They are behind the drivers side kick panel like you said. I did not use a fuse on the line to the battery. What amp fuse should I use? The factory harness is utilizing that 30 amp breaker. I already orded a replacement switch and I'm in the process of putting it back to factory. The unit does have onboard relays but I believe thay are only rated for 200ma. The relays have to carry the load to actuate the lock poppers. Everything I read said you had to use relays. I wired it up as shown in the above diagram with one minor change. In my system I wired both 87 terminals using a 14 gauge wire straight to the battery. For the positively charged post 85 and 86 I ran a separate 18 gauge wire from the battery. Neither wire was fused. This was supposed to be a quick test wire to confirm the system worked then wire it all into the factory system later. The drivers side rocker switch was obviously damaged in the test. What I don't understand is how the system overloaded unless I have a short somewhere. Before I tried locking/unlocking the system with the keyless system I tested the rocker switches. They worked fine. Then I tried the keyless system and nothing happened. I could hear the relays actuate but the poppers didn't move. Then the switch quit working. Before the switch was damaged there was an audible click when it was pressed in the lock or unlock position. After it was damaged it just moved back and forth. No click. That's when I opened it up and confirmed it was damaged. Because it was a temp test the alarm module was sitting on the finder of my car not mounted in the car. I twisted the black negative wire, yellow wire and yellow/black wires together and put them straight to the battery (negative post). The white and white/black wires were used to go to the relays. The power wire on the alarm was also wired straight to the battery but it does have a factory installed fuse on it. Orange and orange/black are not being used. Not sure if any of that matters but thought it should be known. Thanks for the markup on the diagram. The one that came in the box is actually correct. Still calls it closing and opening though.

Hope this helps and isn’t confusing. Steve G

Most aftermarket keyless systems use transistors to switch the negative 200ma outputs and require relays. Your unit appears to have relays onboard and can be configured directly using the various diagrams for different lock systems. I found this image of the board inside showing the relays. I think a 30 amp blade fuse would be best for the relay setup. The 4 power wires can all be together and then run through the fuse. I’m not sure what caused the magic smoke to be released from the switch but make sure both relays are connected to all wires and functioning as a pair when testing. If you only tried testing 1 relay at a time that would definitely cause issues. They need to reverse power and ground simultaneously when triggered and if all wires aren’t connected then power will be driven into a dead short and fry stuff.Steve G

Another thing is perhaps you may have had your switch/motor wires reversed when wiring to the relays. It’s crucial that they are wired as shown in the diagram. In the kick panel it may be opposite of what you assume. There is probably a good way to test which others may be more familiar with. My first thought would be to pull the switch and check continuity between the switch output and the cut wire in the kick. Make sure you have the relay wires matched up properly with the motor side and switch side for both lock and unlock.Steve G

Here is one way to ID the lock motor wire sides using a DMM : Easy way to tell which side of the cut wire is the switch

and which is the motor, is to cut the wire and then press

the button. If it shows 12v it is the switch side of the

button you just pressed. Some times it isnt always easy

to tell which end goes to the switch and which side goes

to the car.Soldering is fun!

Thanks for all the input guys I really appreciate it. The first time I wired the system up I wired it in such a way that when I actuated the relays it sent 12 volts straight to ground. I immediately realized what I did wrong and felt like an idiot for doing it. I've learned a lot of things that way though. We all do from time to time. The car came wired with power door locks from the factory just no keyless entry. When new the system did not utilize relays just the rocker switch on the drivers and passengers door arm rest. If I understand how the system is supposed to work both legs of the motor rest at ground. When you actuate the rocker switch one side comes off ground and is charged with 12+ volts and to other remains at ground resulting in the motors either locking or unlocking the doors. When the switch is actuated in the opposite direction the opposite action happens. If I have the relays wired up correctly then at rest they simply maintain the circuit in its original uncut configuration. When one is actuated it charges one leg or the other so that the door lock motors lock or unlock. So, simply put they just act like another rocker switch in the system. If the above statement is true and I wired it up correctly even if I had the lock signal actuate the unlock relay it shouldn't do anymore than just unlock instead of lock. Right? I wouldn't think if would ground the system. All I should have to do is swap the negative impulse wires. Right? When testing I had both relays wired up, and they both seemed to work correctly. When I pressed the lock button on the key fob or the unlock button only one relay would fire. One didn't actuate to supply positive voltage and the other negative. Only one actuated to supply positive. The other one does nothing because it is already at ground through the normally closed circuit (87). Please correct me on my understanding of how this circuit works if I am wrong. So far I have burned up two switches and one actuator motor. I'm doing something wrong. It was so disappointing the other day when it failed though, because the way I had it wired up made since. Thanks again for all the help.

The system does not seem to work at all with one switch out so I'll have to wait for the new switch to get here before I can continue to really trouble shoot the system.