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Tachometer acted funny

RangerPilot

RangerPilot

Boom Shaka Laka
2,560
110
Dallas, TX
Just went to fill up with gas (3.19 thank you very much), started the truck and the tachometer just sat there on zero. All other gauges worked fine...put it in Drive, got about a hundred feet away and then the tach came up and caught up and worked fine ever since.

Didn't give me any more issues since then. Any suggestions?
 
Raptor22

Raptor22

4,862
142
Davis, California
Hmm... maybe just a fluke? Sometimes when gauges get older, they start to freeze... maybe thats whats going on.
 
Skandocious

Skandocious

Post Whores Make Me Sick
19,076
655
California
Our 76 MGB does that... Couldn't tell you why, but it does it every time you drive it. I wouldn't be too worried about it.
 
RangerPilot

RangerPilot

Boom Shaka Laka
2,560
110
Dallas, TX
Am I right in assuming the truck gets a rpm signal from a different source than the tachometer? I just don't wanna screw with the truck.
 
Skandocious

Skandocious

Post Whores Make Me Sick
19,076
655
California
Lol, well according to the wiring diagram that I've got here for a 98 Explorer, the signal that comes to the tach on the cluster is just a branch-off from the same signal that goes to what it labels as "the message center". It's just 1 wire from the sensor all the way up to the 'message center', and near the top it branches off to the tach.

My gut feel says the tach is just getting old... Is the engine operating normally during this time of no RPM showing?
 
john112deere

john112deere

caffeine junkie
Staff member
10,807
405
central Vermont
Skandocious said:
Is the engine operating normally during this time of no RPM showing?
Click to expand...

How 'bout the transmission. (I'm nearly positive they were computer controlled by that point...if not, disregard.)
 
Skandocious

Skandocious

Post Whores Make Me Sick
19,076
655
California
john112deere said:
How 'bout the transmission. (I'm nearly positive they were computer controlled by that point...if not, disregard.)
Click to expand...
My shifting patterns are largely controlled by the throttle position sensor. It's quite possible that engine RPM plays a factor in the shift patterns too.
 
RangerPilot

RangerPilot

Boom Shaka Laka
2,560
110
Dallas, TX
Tranny acted and shifted normally, and yes it's computer controlled (a 5R55E). RPM based on the engine sound was rock solid the entire time.

I drove the truck another time this afternoon and it gave no issues, so I'm guessing it was just a one-off fluke, so I'm not too worried about it. If it does it again (and for a longer period of time) I'll consider trying to fix it.

Hey Chris, where did you get the wiring diagram for it? I've been looking for one myself.
 

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