MY TACHOMETER AND SPEEDOMETER DONT WORK

[RobbieLSC]

Hello Guys , I own a 1989 Lincoln Mark 7 LSC / 5.0L ...

I received this car as a gift from my uncle a year ago, and all is gravy , I don't mind when something brakes in the car. I am able to fix or replaces the parts on my own most of the time. I have been fixing one thing after another with this car since I owed it. Once I fix 1 problem another problem appears. I think this car hates me because I got it for free, anyways lol.
I was driving to 7/11 one night, and this nice guy came up to my car and asked me if I knew my rear parking lights were not on, which I wasn't aware of them not been on, better then having a cop letting me now. I made it home without any problems. The next day I took off most of the trucks rugged panel to reveal the taillight, and found out that 1 of the parking bulbs must of vibrated out of the socket a little, and I pushed it in , and found out it fixed both of the parking lights. Awesome problem solved. I ended up replacing both rear parking bulbs to be on the safe side.
Soon as I completed the repair on the rear parking lights, I took my car out for a drive, and I instantly noticed that my speedometer or tachometer did not work at all. They both didnt even move a little. My gas gauge and temp gauge work fine without any problems at all, expect for of course both the speedometer or tachometer.
I remember reading in a few posts that could be a problem with the ignition switch . I went to AutoZone today , and picked up the switch , replaced it within 10 minutes to find out that it wasn't the problem. Which I didn't mind about at all , because the old switch looked a little old and worn out , and looked like it needed to replace anyways.
I did take my dash apart today , and also took a look at the Cluster to inspect anything out of place or loose or maybe missing, and I didn't notice anything at all.

I have also read about the black and orange wires in the back of the cluster is known to loose ground or some sort, and they need to be re-grounded somewhere else , but I seen if you have a problem with the tachometer and gas gauge only , mine is just the speedometer and tachometer, all other function well. Could this very well be the problem with my gauges or it something else.
Does anyone have any idea what I am doing wrong, or any ideas on how to fix my problem I am having . Thank you to who ever can figure out my problem . Thanks

[RobbieLSC]

Oh ya, I also checked all the fuses in the fuse panel ,and all the fuses are in working order. I also checked to see if the cruse control works , and it does without any problems. That tells me it can't be the speed control sensor on the transmission , i'm guessing of course...

[oldschool1]

Start by replacing your REAR LAMP OUT bulb.

Do all four tail light bulbs work properly?

[RobbieLSC]

Yes all four of my tail lights work fine without any problems. Matter of fact all of my parking lights, and headlight work fine with out any problems. Would replacing "check taillight" bulb make any difference in the speedometer or tachometer cluster to be working or not? Can you give me any ideas where to check to get see why the speedometer and tachometer cluster isn't working .. Could it be a bad ground? or maybe my fuse panel or some sort. I completely have no idea what to do ,I am almost ready to take my car to a auto repair shop , which I really don't want to do. Any help would be grateful . Thanks in advance...

[WHITEOXLSC]

Well, I am looking at my 90 EVTM manual and the tach, speedometer, temp and gas gauge all receive power via red/yellow wire fuse #18 (10a). The ground for the fuel gauge and tach is supplied from the fuel sender unit. The ground for the speedometer and temp gauge is via black wire and grounded at connection point G200 (behind instrument panel, right hand side of steering column. So it has me baffled as to why you are having your problem. If it was a power problem ALL gauges would not function, if it was a ground issue either the fuel and tach would not function or the temp and speedometer would not function. Check power at the red/yellow wire (key in run position) and check for proper ground on the black wire and the orange wire. Could be a possible problem with the instrument cluster itself. Make note this is from the 1990 EVTM and yours is a 1989, so I don't know how much they changed (if any) to the wiring.....

[oldschool1]

Yes all four of my tail lights work fine without any problems. Matter of fact all of my parking lights, and headlight work fine with out any problems. Would replacing "check taillight" bulb make any difference in the speedometer or tachometer cluster to be working or not? Can you give me any ideas where to check to get see why the speedometer and tachometer cluster isn't working ..

I don't have an EVTM with me at this moment so I'm basing my reply on first making sure that everything in the system is corrected back to factory and then working from there. The failures that we ~normally~ experience in a 1990 - 1992 is either all lights or function out in the cluster or a failure to accurately read ONLY the fuel and RPMS when the lights come on automatically. Te latter would be a ground issue, possibly through another component or switch or relay. Since the functioning of the cluster (illumination and sensor reading) has only two sources for power, that's kind of easy to trace out on the power side. The functioning of the cluster (illumination and sensor reading) is also Dependant on other components and ~their~ shared grounds. Without an EVTM I cannot go any further without suffering from foot-in-mouth syndrome

Could it be a bad ground? or maybe my fuse panel or some sort. I completely have no idea what to do ,I am almost ready to take my car to a auto repair shop , which I really don't want to do. Any help would be grateful . Thanks in advance...

WHITEOXLSCs recommendations are based on our EVTMs and tells us what to look for and test first.

As for your fuses, illumination and operation would not change states with driving conditions. The components or accessories would either be always on or always off.

[RobbieLSC]

First I would like to thank everyone for your input. You guys made good points, and I am going to do further inspection to the cluster wires to make sure they are getting the proper input. I would like to add that I bought a new Speed Sensor today, and replaced it without any problems , and my SpeedO and TachO are still not working. I did realize that today my gas gauge was acting up. Once I start my car , the gas gauge will fly to Full Gas Tank position , and then it slowly goes down to the correct gas level, which is half of tank. I am starting to believe that maybe it very well is the gauge cluster that is broken . Like I said in my past posts , I replaced the ignition switch , and speed sensor , and still no difference . I am guessing my next step would be replacing the cluster, what do you guys think? Thanks

[oldray]

Disclosure / warning: Mark VII rookie but life expert (way past best by due date).

Have you tried running a temporary ground wire from the fuel tank sending unit to a known good ground?

[WHITEOXLSC]

First I would like to thank everyone for your input. You guys made good points, and I am going to do further inspection to the cluster wires to make sure they are getting the proper input. I would like to add that I bought a new Speed Sensor today, and replaced it without any problems , and my SpeedO and TachO are still not working. I did realize that today my gas gauge was acting up. Once I start my car , the gas gauge will fly to Full Gas Tank position , and then it slowly goes down to the correct gas level, which is half of tank. I am starting to believe that maybe it very well is the gauge cluster that is broken . Like I said in my past posts , I replaced the ignition switch , and speed sensor , and still no difference . I am guessing my next step would be replacing the cluster, what do you guys think? Thanks

OK now we might be on to something..... That sounds like a possible grounding issue. Very possible the black ground wire has become open or resistive and the circuits are "searching" for a ground through the fuel sender or other circuits. Check the grounding points by the battery also, the one bolted to the radiator support becomes corroded over time, also check this two wire connector (C103) by the compressor (next to the battery), this is the main negative ground connection. Check for a good solid ground at the cluster too. Also make sure you have a full 12 volts (with key in run) on the red/yellow wire.



Hope this helps....

[RobbieLSC]

Thank you so much. I will check all the ground wires that you pointed out to me. I think you are very correct with my issues. My car is known to have poor grounded points , It seems that something is malfunctioning every day in my car , with grounding wise. Thanks a lot for your help ...
I have another issues that has just started two days ago. The DOOR AJAR light does not come on when I open any of the doors , trunk , hood . The interior lights turn off like they should , but once I close all the doors , the DOOR AJAR warning light will lightly dim on .I then decided to do a little test, and I noticed that when I have either of the doors wide open, and push the door jam switch with my fingers , the interior lights shut off like they should, also the DOOR AJAR waring light does turn on or nothing at all, but once I slam my door shut , the door ajar light will then turn on , with a very dim light.

As I said before you have gave me wonderful tips on where my problem may be, could you maybe point out some other grounding spots , that I could check out and inspect to see if they need a good old wire brushing or some sort. Thanks a lot.

Also let me add , that a few month ago , My left factory fog light had stopped working , I thought I blew a bulb, but then find out that I lost a grounding on the right fog light, and had to rewire a new ground wire , which I ended of doing on both fog lights for prevent any future problems , I figure this may help you with trying to figure out what the hell is going on with my wiring system in my car.
I have to say , my 1989 Lincoln Mark 7 LSC / 5.0 , with 140,9990 miles , runs and drives prefect , with no engine problems , it's just the grounding problem I am having, I am afraid to drive my car now, in case it may get a short and catch ... Any guesses would be grateful , and thank you so much in advance

[RobbieLSC]

BTW , thanks a lot for the picture , it is very helpful. Also ur Air Pump looks brand new , very clean looking . The one in my car looks like a piece of junk compaired to yours

[WHITEOXLSC]

BTW , thanks a lot for the picture , it is very helpful. Also ur Air Pump looks brand new , very clean looking . The one in my car looks like a piece of junk compaired to yours

Thanks
It looks new because it is. When I saved my car from going to the crusher, one of it's issues the previous owner didn't want to repair, was the air ride system. Instead of just replacing the components that it needed, I opted to buy a kit and replace everything (air springs, solenoids, drier, and compressor). Everything was original so I figured that to avoid future problems, I would just do it all in one shot. It's cheaper in the long run.....







Cheers.....

[WHITEOXLSC]

By the way, check that connector by the battery, it's the ground for A MAJORITY of the cars systems.... Mine was corroded to the point that one wire became "open" and it caused all sorts of weird things to happen Check the engine block ground, (negative battery cable) as well as the one that from the block to the firewall. Also check the gas tank ground strap (if your car has one) for a good connections.....

[oldschool1]

RobbieLSC,
I had 30 minutes to kill so I scanned, edited, and published the three pages from the 1989 EVTM that relate to your 1989 Analog Cluster.
Pretty cool stuff.
I like tracing down gremlins.

[WHITEOXLSC]

RobbieLSC,
I had 30 minutes to kill so I scanned, edited, and published the three pages from the 1989 EVTM that relate to your 1989 Analog Cluster.
Pretty cool stuff.
I like tracing down gremlins.

Thanks John for the scans, I'm sure this will help out for sure. I noticed that there are some changes they did from 89 to 90, so some of the things I was pointing out are a little different... BTW I like to find out why things are acting weird too. These cars can have many gremlins, but with persistence and a little understanding of how the systems work, one can usually find where they are hiding......

[oldschool1]

Bruce,
I own the following shop manuals and EVTMs to cover our Lincoln Mark VIIs based on engine and interior:
1984 - for 1984 only
1986 - for 1985 to 1987
1989 - for 1988 and 1989
1990 - for 1990 to 1992

The 1990 books will not help with the brake changes in the 1992s.

The manuals have paid for themselves several times over and EVERY Lincoln mark VII owner should have a set even if they take their cars to a shop. The mechanic will thank you

[WHITEOXLSC]

Bruce,
I own the following shop manuals and EVTMs to cover our Lincoln Mark VIIs based on engine and interior:
1984 - for 1984 only
1986 - for 1985 to 1987
1989 - for 1988 and 1989
1990 - for 1990 to 1992

The 1990 books will not help with the brake changes in the 1992s.

The manuals have paid for themselves several times over and EVERY Lincoln mark VII owner should have a set even if they take their cars to a shop. The mechanic will thank you

Yep have a set for my 1990. First thing I bought off EBAY, when I got the car....