Speedometer help sorry its long

[240sxPreludeSESI]

Well we bought a 1991 240sx se coupe auto dohc well i have had to fix just about everything on this damn car haha but i love the car. Well I'm not going to get off subject saying all what i had to fix, but the digital speedometer and hud and odometer were not working. I did a search did the capacitor test did not work. So i went to the junkyard and got a analog cluster and harness for $50! It was from a 91 240sx se auto dohc fastback. Well i put the analog one in and drive everything worked except the speedometer and odometer and trip.

So at this point im thinking damn its the speed sensor. Well i unplugged it and re-plugged it and then screwed it in. The speedo needle then bounced around a bit but the odometer worked and trip worked fine all along. Then after like 3 mins of driving the speedo got smooth and worked PERFECT for about a week.

Then two weeks ago when i took the drivers door apart to fix the damn window amp that blew making the window not go down! I started the car to play with my new found window going up and down lol. I noticed the speedo was at 40mph with the car idling! I shut it off and it went to zero turned it back on didnt work at all! BUT the odometer and trip work perfect. I go inside to search to see what it could be. Go outside it works fine but is a little bouncy. They last night it didnt work at all everything works but the speedo. I then was mad and hit the top of the dash and it bounced to the speed i was going i gave it gas and it worked fine! Few mins later it fell to zero!

I can tap it and make it work for a little while i noticed after 15mins of driving it works a lot easier hardly have to tap it to get it to work. Also if i hit train tracks hard it will work and stay working until i turn the car off! and the whole time everything else works. So im thinking its maybe the speedometer head or wiring, loose connections, dead spot in circuit or cluster itself it did come from a junkyard! I guess i'll get the meter out and go to town looking for loose wires or sauder.

Any ideas on what i should do?? Has anyone experienced this and fixed it??

[Luis240]

Im sorry i have nothing to help,But I will like to also find out whats wrong because i just bought an 89' hatch and the speedometer does the same thing. Ill be driving and out of no where the damn thing turns on and then when I stop at some lights or the next time i look at it, it drops back to zero.And like yours i parked my car and it was idleing and the speedo was at 20mph.

So i don't know i'm lost

[AndrewMinervini]

its supposed to plug in to the plug that comes in from the passenger side wheel well right? mine doesnt read at all

[Zell311]

my speedo is stck all the way up? and wont budge for anything