Tach not working
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Joined: Apr 2013
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From: Connecticut
Tach not working
Hi everyone. 1993 Dakota here. I'm trying to get it to pass emissions, but they need the tach to do a dyno run. It figures that the only thing on the cluster that is not working is the tach. I just had the truck completely apart for a new frame, and the tach worked fine before the disassembly. Now it does not work at all. I have the cluster out of the truck and the needle moves when I rotate the cluster assembly. Speedometer works fine, and the shift light also functions as it should. I have the FSM so I will troubleshoot it, but I was wondering if anyone had this same problem so I can have a shortcut. 
. Damn registration runs out on Sunday. Late fees piling up every which way...
. Damn registration runs out on Sunday. Late fees piling up every which way...
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Joined: Apr 2013
Posts: 941
Likes: 22
From: Connecticut
Thought I'd update this. I started troubleshooting.
-Tach/horn fuse (in-car panel 15 amp #6) is good.
-Horn works
-Removed the tachometer module (piggyback PCB nestled on top of the cluster) or whatever you call it, cleaned contacts, reinstalled. Also I bent the contact prongs on the tach module in hopes of achieving better contact
-There is continuity between the PCM tach output (#43 pin) and the cluster (blue/gray wire)
-I have not tested to see if the PCM is actually emitting the signal it's supposed to. I probably should have done that, oh well.
I'm buying a new cluster.
-Tach/horn fuse (in-car panel 15 amp #6) is good.
-Horn works
-Removed the tachometer module (piggyback PCB nestled on top of the cluster) or whatever you call it, cleaned contacts, reinstalled. Also I bent the contact prongs on the tach module in hopes of achieving better contact
-There is continuity between the PCM tach output (#43 pin) and the cluster (blue/gray wire)
-I have not tested to see if the PCM is actually emitting the signal it's supposed to. I probably should have done that, oh well.
I'm buying a new cluster.
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Joined: Apr 2013
Posts: 941
Likes: 22
From: Connecticut
New tach going in Monday hopefully.
I don't understand why they actually need the tach to do the test. I mean, I get that it is supposed to be a dyno run and it therefore is logical they'd need to read rpm, but so many cars/trucks didn't come with tachs. It doesn't matter for OBD2 vehicles but how do they test OBD1 vehicles with no tach?
Oh well, I want the tach to work anyway so I want to fix it.
I don't understand why they actually need the tach to do the test. I mean, I get that it is supposed to be a dyno run and it therefore is logical they'd need to read rpm, but so many cars/trucks didn't come with tachs. It doesn't matter for OBD2 vehicles but how do they test OBD1 vehicles with no tach?
Oh well, I want the tach to work anyway so I want to fix it.
Thread Starter
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All Star
Joined: Apr 2013
Posts: 941
Likes: 22
From: Connecticut
So I bought a whole new cluster, unplugged the tachometer module and put it on my old gauge cluster. Bingo bango, we have arrr pee emms. Unfortunately I had to buy a whole cluster to get it to work...$50 isn't bad though.
