Tach problem, new sensor
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Junior User
Joined: Jun 2004
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Tach problem, new sensor
I replaced my tachometor sending unit after much hesitation hoping this would be a easy cure. It did not fix it as I had thought it would not. It first started going off and then coming on by itself every once and a while until it finally stopped and would not come back on at all. What else should I check? Is this an electrical problem somewhere?
Thanks for your help,
Derek
Thanks for your help,
Derek
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Junior User
Joined: Jun 2004
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I just checked the plug connection at the sensor (the one that goes back to the tach) and it is grounded at both pins. It shows 12 volts if I put my meter on the pos side of the battery and negative in the pinholes. Is this what it should show? How does the instrument cluster come out so I can see what is reading directly behind the tach?
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Take the top of the dash off.
Remove the light switch **** and the wiper ****, there are little tabs on the back of them that you pull to release them.
Remove the insturment cluster trim.
Remove the insturment cluster, speedo cable must be removed before it will come out very far.
The electrical connector is on the right side and needs to be removed before it will come out very far.
The electrical connector could be loose causing your problem.
The tach could also be bad.
Ford does not have them anymore.
Remove the light switch **** and the wiper ****, there are little tabs on the back of them that you pull to release them.
Remove the insturment cluster trim.
Remove the insturment cluster, speedo cable must be removed before it will come out very far.
The electrical connector is on the right side and needs to be removed before it will come out very far.
The electrical connector could be loose causing your problem.
The tach could also be bad.
Ford does not have them anymore.
Thread Starter
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Junior User
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Thanks Dave, I had it as far as the cluster but it was being held in by the wiring so I went to get a service manual before I tore something up. once I get the cluster off I am assuming I could check the wiring with my meter to see if it is good to that point, I am also assuming that the sensor is simply an interuption in the circuit, it may read to fast to be able to test though. Thanks again!
Derek
Derek
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Joined: Feb 2004
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From: The Gorge, Oregon
UMmm'.. I'm not sure what the signal range should be
I don't have a service manual yet... so i can't say what it should be.
However, you should be getting something with it connected properly.
If not then it's the signal wire (hot) or the ground wire (-) not completing the path circuit to operate the tach.
Unless the tach is actually defective which it doesn't sound like it is.
You can also disconnect the signal wire from the tach and connect it to the + voltmeter lead and then connect the - voltmeter lead directly to a ground jumper wire to the negative battery post. This way you are bypassing or checking for any ground problems you might have as well.
Again not knowing our voltage range signal can be a problem.
So can someone with a service electrical troublehooting manual maybe help out as well. I hope this helps get you in the right direction for testing things out if nothing else.
However, you should be getting something with it connected properly.
If not then it's the signal wire (hot) or the ground wire (-) not completing the path circuit to operate the tach.
Unless the tach is actually defective which it doesn't sound like it is.
You can also disconnect the signal wire from the tach and connect it to the + voltmeter lead and then connect the - voltmeter lead directly to a ground jumper wire to the negative battery post. This way you are bypassing or checking for any ground problems you might have as well.
Again not knowing our voltage range signal can be a problem.
So can someone with a service electrical troublehooting manual maybe help out as well. I hope this helps get you in the right direction for testing things out if nothing else.
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Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
I do not know the actual voltage that the signal current is, but if you check across the two wires from the sending unit it sends out a voltage to the tach. The voltage should increase with engine speed.
Watch the printed circuit on the rear of the insturment cluster, it is kinda fragile.
Watch the printed circuit on the rear of the insturment cluster, it is kinda fragile.
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New User
Joined: Aug 2004
Posts: 4
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From: Washington
I am having very similar problems on my 93. varable tach and hard shifts from the E4OD. I have looked for the ground wires you talked about but am unfamiliar with where the ABS module is located. Can you help?
Junior User
Joined: Feb 2004
Posts: 53
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From: The Gorge, Oregon
Cj74ever,
Check the drivers side "inner" fenderwell first, and all the grounds around any electrical components in that area as well as body grounds. Does or can anyone get pics of this area for him, if he needs it.? I hope this helps.
Check the drivers side "inner" fenderwell first, and all the grounds around any electrical components in that area as well as body grounds. Does or can anyone get pics of this area for him, if he needs it.? I hope this helps.
Thread Starter
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Junior User
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Originally Posted by bigsquirt
Cj74ever,
Check the drivers side "inner" fenderwell first, and all the grounds around any electrical components in that area as well as body grounds. Does or can anyone get pics of this area for him, if he needs it.? I hope this helps.
Check the drivers side "inner" fenderwell first, and all the grounds around any electrical components in that area as well as body grounds. Does or can anyone get pics of this area for him, if he needs it.? I hope this helps.
New User
Joined: Aug 2004
Posts: 4
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From: Washington
I replaced my Throttle Position Sensor this weekend and the hard shift problem went away. I still have an intermittent tach failure. It only occurs at idle. As soon as I step on the gas the tach picks up and works correctly. The other symptom that I have is that as the truck if moving and I release the gas and the tach goes to zero the overdrive off light will flash. It is acting like a ground in the system but I cannot be sure. Thanks for any help!
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Junior User
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Originally Posted by cj74ever
I replaced my Throttle Position Sensor this weekend and the hard shift problem went away. I still have an intermittent tach failure. It only occurs at idle. As soon as I step on the gas the tach picks up and works correctly. The other symptom that I have is that as the truck if moving and I release the gas and the tach goes to zero the overdrive off light will flash. It is acting like a ground in the system but I cannot be sure. Thanks for any help!