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Greg Smith Power door locks writeup PRE-1991


NAXJA Member # 13
NAXJA Member
I want to do this today and need the article that was posted on the OEM forum sometime ago. HELP!
Here is a current version of the writeup.

Power Door Lock Fix for Reluctant Locks on Pre 1991 Jeep Cherokees
(for post 90 models with a similar problem I woud check the relays in the passenger side kick panel)

The Problem:

Some (usually not all) of the power door locks stop working, or more commonly work inconsistently on the lock and/or unlock position. The problem usually starts when the Jeep gets older and the locks become stiffer. Cold weather seems to cause the most problems. The rear hatch and rear doors seem to the most troublesome since they are on the end of the circuit and experience the largest voltage drop.

The Cause:

The cause is a design flaw which causes a loss of 2 volts. As the Jeep gets older and the locks become stiffer and the connections develop some resistance the amount of voltage that gets through the system is no longer enough to work the power locks near the end of the circuit. With the pre 1991 wiring all the power for the power door locks passes through the passenger door lock switch regardless of whether you trigger that switch, the driver’s side door switch or the remote keyless opener (if you have it). Power leaves that switch going to the door locks through the tan wire for unlock and the light green wire for lock.

The power goes from the passenger door switch to a splice in that door for the power lock in that door and then goes out the door and into the kick panel in front of the door on the passenger side. By the time the power gets to the kick panel it has lost about 2 volts. I replaced my passenger side switch suspecting a bad switch but still lost 2 volts out of the switch. I then did a full continuity and resistance test on the switch per the factory service manual and found no problems. I have never figured out why this happens but apparently Jeep could not either since they changed the wiring starting in 1991 to compensate for this problem. (Note the wiring change can be done like the post 1990 models but the fix I provide below is a lot easier in my opinion.) After the now lower voltage gets to the passenger side kick panel it goes under the carpet and over to the driver’s side and hits a master splice under the front floor carpet for the wires going to the driver’s side front and rear doors and the passenger side rear door. I unwrapped the tape around the splices and checked all the splices and they were clean and tight. Then I measured the voltage at the remaining power locks. By the time the voltage gets through the master splice is loses another 2+ volts and is not enough to power the locks consistently when they become stiff from old age or cold weather.

The Fix/Repair:

First make sure you are getting around 12 volts of power to your passenger side door switch directly or when you trigger the lock or unlock switch from the driver’s side or by the remote. You can test the voltage with a multi-meter at the wire harness connector in the passenger-side kick panel where the dark green, white and red wires go into the front door.

Assuming you have a full voltage supply to the passenger side switch, the fix is to install two relays in the passenger-side kick panel on the lock and unlock wires coming from the passenger side switch. The relays will increase voltage back up to 12 volts to compensate for the loss caused by the passenger side switch. With the voltage increase provided by the relays, the voltage at the remaining power door locks is increased by approximately 2 volts, enough to power all the locks, even in cold weather. This of course assumes that no wiring problems exist from the splices to the door locks. If you still have a problem at a particular door lock measure the voltage and make sure it is over 9 volts. With my fix it should be closer to 10 and perhaps 9 at the rear hatch.

The relays to use are 5 blade, 12 volt, 30 amp minimum rated relays with blades marked 85, 86, 87, 87a and 30. These relays are the same as those used for the keyless remote relays found in the passenger-side kick panel so you may find them cheap at the bone yard. You can also find them in automotive electric supply stores. Look in the section that has lighting upgrade supplies. For an easier install it is also best to buy wiring sockets that fit the relays. Here is a link to partsexpress.com an online supplier that has relays and sockets at reasonable prices. I used 2 bosch relays # 330-070 and 2 sockets # 330-075 (although 1 dual socket 330-078 could be used I believe). http://www.partsexpress.com/webpage.cfm?&Webpage_ID=3&DID=7&CAT_ID=47&ObjectGroup_ID=31&SO=2

Here is how I did the wiring: I used the two 12v relays. They have 5 blades: 86 is trigger pwr from the passenger dr switch; 85 is ground; 87 is the new pwr source; 30 is the path to the lock and 87a is to ground (in this application). I cut the Lgreen and tan wire about 5 inches forward (toward the front of the Jeep) of the wire harness connector that connects the wires to the wires coming out of the passenger frnt dr. In this example I attached the tan unlock wire coming from the passenger frnt door to 86 and 85 to ground; 30 is attached to the tan wire going to the door locks; and 87a is to ground. I used the new 10 gauge pwr line I had previously run to the battery/starter relay post with a 30 amp inline fuse. You can take off pwr from a splice on the red pwr going into the passenger door instead. (The same approach is used for the lgreen wire using the other new relay for for the lock circuit.) The key to making this work was 87a to ground. When the lgreen or tan wire are not in pwr mode they provide ground path to ground through the driver’s side switch. With my new relays I substituted a new body ground instead. As a result I increased voltage and created new better grounds. The locks now all slam open and closed even in very cold weather. Hope this helps. At least 30 people I have heard from have done this mod with great success. Greg
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I am in the process of trying to fix my intermitent electric door locks on my 89 xj and found this artice. I was really excited, went and got all the relays and I in the process I thought there might be a problem.

This shows 87a as a ground and 87 as 12v power. Plain and simple this can not work.

Also, I found that it recommends 30 as tan to other locks instead of 12v power??

In any case, I am still in the process of trying to put it all back together and get it working and for the life of me I can not get it to work and up the voltage to the drivers side door locks.

Any help or anyone who has used this article I would really like some help on any clarification you might be able to provide. If I figure it out, I will let you know asap.

All in all the article is very helpfull.

No I am really confused!!

I tried several conbinations with the relays and could not find one that worked.

So I took them back out and put everything back to stock. Now they all work perfectly (even the rear hatch, that almost never worked). so I checked the voltages at both front doors and they are both over 12volts?? When I started the voltage at the drivers door was barely over 6volts.

I have no clue what I did, but I would still love any feedback on how to instal the relays because I have another jeep to do the electric locks on as soon as I figure it all out.

Not sure what you did to increase voltage when you put everything back the old way but hopefully it is a permanent fix. In my experience I have made the locks to temporarily work better by cleaning some connectors but always it reverted to the problem later.

Anyway the wiring design I provided with the relays has worked for probably over 40 or more people on this forum and the jeepsunlimited.com board. You probably had the lock and unlock wires each wired wrong. As stated before you need two 5 blade 12 volt relays one for the lock circuit and one for the unlock circuit. Each relay has a pull side 85 and 86 and a switch side 30, 87 and 87a. The pull side pulls the switch from 87a to 87. On this application both 86 and 87a are wired to a ground. 86 is wired to the tan lock wire (in this example) coming from the passenger side front door switch - splice into the wire just after it goes out of the door and into the front passenger side kick panel. The other end of the lock wire that you just cut (the part going to the lock motors) should then be attached to blade 30 on the relay. ***That is often the part people get reversed. You 12 volt s*** Your 12 volt supply line should be attached to blade 87.

Once wired the lock relay at rest without being triggered supplies the needed ground path through blade 87a for the unlock circuit if that is triggered. Once you trigger the lock switch power goes from the passenger side switch out the door through the tan wire into the kick panel to your splice then to the relay blade 86 and to ground 85 completing the circuit and also pulling the switch side of the relay from ground 87a to power 87 allowing your better 12 volt supply to go to blade 30 which is attached to the other end of the tan lock wire you spliced and from there on to your lock motors. For the unlock relay it is the same only using the light green unlock wire instead. Good Luck. Greg
first let me say that your article is wonderful and I really appreciate all the work you did, because it made the whole issue worth fixing for me. When I put everything back together I did put dialectric grease on all the contacts and I did a splice that someone before me had obviously done (and I suspect this might have been the loss in voltage culprit). In either case I now have more than 12volts on both sides so I believe it will be a permanent fix.

However I still have my mother in laws jeep to do so I still want to understand how to do the fix with the relays.

I did use 2, 12volt 30amp relays (five blades each) and they are marked with the same numbers as yours. But from your description they definetly operated differently than yours. My relays utilize 30 as input 12volts (fused), 85 as ground, 86 as switching means, and 87 and 87a as output to accessories. So in my case I can obviously not hook them up the same as you have because I would short out the relays with power in 87 and ground on 87a. So what I tried to do was use your explanation and re-wire it with my relays. What ended up happening was that everything worked fine on the pass side door, but none of the other locks would lock or unlock.

I think that I will attempt the other jeep and see how it works, in the mean time I will do a little research and see if I can not fine another 5bladed 12v 30amp relays.
Thanks for your time and help.

Its great you found a fix for your problem without the relays. However, if you later need to do my fix I think you might want to give the relays another try. In my opinion your relays are the same as mine. These relays can be used in a couple of ways - one as you describe and the other as I describe. Yes you could wire the 12 volt to the 30 blade but only if you needed to switch 12 volts from the 87 to the 87a blade and back and forth to direct the current to two different accessories at different times. But that is not what you need to do here. Here you need your relay to provide power to the lock motor thru 87 and when not doing so it needs to function as a ground circuit through 87a. Thus here you need to have the 30 blade wired to the wire going to the lock motors and the 12 volt wired to 87 and 87a wired to a ground. The trigger wire from the passenger side switch is wired to the 86 blade and 85 to ground. All of which is described in more detail in my previous posts. Good Luck. Greg
I will definetely be trying again (just on my mother in laws jeep instead of mine) and I will let you know how it turns out.

Thanks again for yall your help.

Re: Greg Smith Power door locks writeup

Add another fix to your belt, Greg. I did have the 30 and 86 backwards first, but reread the post and got them switched around. Thanks a bunch.
Re: Greg Smith Power door locks writeup

flexj said:
Add another fix to your belt, Greg. I did have the 30 and 86 backwards first, but reread the post and got them switched around. Thanks a bunch.

:cheers: Another satisfied customer!! Glad it worked for you. No more annoying reluctant locks. Greg
Greg Smith Power door locks writeup

Wich wire is the ground wire? What color? Anyone Know? My locks are getting annoying. Thanks.
Re: Greg Smith Power door locks writeup

Goonowsky said:
Wich wire is the ground wire? What color? Anyone Know? My locks are getting annoying. Thanks.

The only wires on the car that you splice into are the lock (light green) and unlock (tan)wires. You provide your own power wire and ground wires. Read my writeup again and it should be clearer. Let me know if you need help. Greg
Re: Greg Smith Power door locks writeup

I tried several different combinations also with out luck...then I re-read Greg's instructions again r-e-a-l
s-l-o-w and started over. Greg is the man. Too bad the wife totalled it a few months later, LOL.
Re: Greg Smith Power door locks writeup

Hi Gregg,

I'm glad this subject came up again. I tried this last summer....sweat pouring down while upside down in the passenger seat. I wasn't successful but will attempt once more very soon. I put the diagram into a Visio (.VSD) file to try to make it clearer for people like me that are electrically challenged :confused1 and have it to offer to anyone who is interested. I think it is correct. Anyone interested in the file can email me at either [email protected] or [email protected].

Thanks for offering your advice to us.

Jay in MA
Re: Greg Smith Power door locks writeup

Hello Greg Smith,

Could you email me when you get a chance? I would like to send you the diagram I made using your handwritten diagram. I think I can get it into a Word doc that you can open and check for accuracy. Might help some people but I want it to be correct.

Thanks...Jay in MA [email protected]


Hi Josh,

Sorry, I'm not the guy that created this solution. I couldn't get it to help my
problem with my first shot at it. I'll try it again at a later date.

All I did was take a hand written diagram (by Greg Smith) that I saw somewhere
and convert it into a Visio drawing. I'm not sure it is correct and hope that
people like you can tell if it is in fact correct. You need to make the four
ground wirees/connectors and then connect all four at the good grounding point
of your choice.

Jay Welch
Abington, MA
Member Cape Cod British Car Club CCBCC http://www.capecodbritishcarclub.org/

-- Josh Almeida <[email protected]> wrote:
Thanks for the diagram! It's great!I have just one
question. The black wires that meet at "four blades to
ground", where exactly are they? In my kick panel I
see two relays that were already there. Out of the one
closer to the front end of the jeep, there is a black
wire, but theat is the only black wire I can find. Is
that the one? Please help. Thank you very much.
Re: Greg Smith Power door locks writeup

Jay you have mail. Greg
Re: Greg Smith Power door locks writeup

Just wanted to send a HUGE thanks to Greg Smith! I've been goin' out of my mind for the longest time trying to pinpoint the problem with the power locks in my '87 XJ...until finding his writeup. I actually bought three lock actuators off eBay before finally finding this thread, but they made no difference. Even taking out all 4 door latch mechanisms and cleaning them didn't help (although they did kind of need cleaning and re-greasing).

I think I may have woken up my neighbors with my celebratory shouts after finishing the 20 minute job, but oh well!! That first "chunk" sound of all 5 locks slamming from locked to unlocked was just.......sweet. I was totally amazed that all it took was about $7.00 in parts and a little time!

Greg - YOU ROCK!!

To anyone having problems with this fix, just read Greg's article carefully (maybe a couple of times) and maybe print it out for reference. My install went without a hitch. No problems at all! Worked the first time!! Just be sure to find a good +12V wire and a good ground.

Thanks again, Greg!

Re: Greg Smith Power door locks writeup

Pyro, Glad it worked for you. It is amazing how annoying those reluctant locks can be. Yes I danced around and screemed out loud when I finally fixed them after yrs frustration. With so many happy door lock fixers maybe we should start a new club -- the dancing door lock fixers! :party:

Re: Greg Smith Power door locks writeup

I have all of the parts together, harness made/labeled and will be installing Saturday in my '89. I'll be using a new ground point and will pull a fused 12 volts from the battery.

I'll let you know how I make out with the upgrade.
Jay in MA
Re: Greg Smith Power door locks writeup

You can add another notch to your belt there Greg :) Thanks for the good write up, works like a charm.