Speedometer problem

Tiny
JARRAHQ8
  • MEMBER
  • 2015 FORD EXPLORER
  • 3,000 MILES
This is a brand new vehicle. I notice that the needle sometimes is at zero then after driving and parking and leaving it idle with engine off the needle slightly moves above zero. Then I start car it is still above zero slightly. I drive it around and stop it is still above zero. Then when I leave it to rest it goes back down to zero like it should. This cycle goes on and on. What is the problem?
Do you
have the same problem?
Yes
No
Saturday, July 30th, 2016 AT 7:34 AM

5 Replies

Tiny
RIVERMIKERAT
  • MEMBER
Is it reading while you are driving? With electronic speedometers (especially) this can happen.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 8:02 AM
Tiny
JARRAHQ8
  • MEMBER
Yes, while driving it reads. But the needle starts slightly above zero and at times needle starts exactly on zero. When the needle starts above zero the speedometer while driving will read a few km/h mph higher then when it is bank on zero.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 8:06 AM
Tiny
RIVERMIKERAT
  • MEMBER
This could be residual voltage in a capacitor in the circuit or PCM/Speedometer/instrument panel. Or it could be an intermittent problem with the resistor/varistor inside the speedometer. Personally, until it gets to be around 5% inaccurate, I would not worry about it.

What engine and trim level? I will see if I can find a schematic that gives any information.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 9:12 AM
Tiny
JARRAHQ8
  • MEMBER
Base model 2015

Engine and Performance
Base Engine Size: 3.5 L
Base Engine Type: Flex-fuel (FFV)
Cam Type: Double overhead cam (DOHC)
Cylinders: V6
Torque: 255 ft-lbs. @ 4000 rpm
Turning Circle: 39.2 ft.
Valve Timing: Variable
Valves: 24

Also I took it to the dealer nothing came up when the did a program run. They said they did a pcm and recalibrated to latest.

But still it has a slight variation with the speedometer like one to two miles out at times when needle is slightly above zero.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 9:46 AM
Tiny
CARADIODOC
  • EXPERT
You are overlooking one important point. Since the early 1990's the gauges are not the simple, reliable spring-loaded affairs that never caused a problem. They are "stepper" motors with a pointer attached. A stepper motor does not have an armature and brushes as we are used to seeing. It has an armature that is placed in a specific orientation by the computer pulsing four electromagnetic coils with varying voltage and polarity. You can verify that by observing that most gauge pointers stay right where they are when you turn off the ignition switch. Even that has changed now too in that some computers intentionally run the gauges back to "0" as part of their turn-off programming.

Once turned off, tapping on the bezel will make some pointers move. If you were to physically push a pointer to some position, it would stay there until you turn the ignition switch on.

As a point of interest, if you did that, or if a voltage spike caused a pointer to jump higher than half scale, when you turn the ignition switch on, the computer is going to run every gauge back to "0", and for the one that's over half scale, it's going to look for the shortest way to "0", and that is clockwise. On most cars there is a stop peg at "0" and the pointer will get stuck on the wrong side of it. All that is needed to correct that is to run engine speed higher than half scale for an instant. When the shortest way to the actual speed is counter-clockwise, the pointer will go there, then follow engine speed back down like normal. The same is true of speedometers. The voltage spike that causes this is most often caused by reconnecting the battery.

Everything you described tells me you do not have a problem. To verify that, visit some similar vehicles on the used car lots and see if they respond the same way. Also, since many people are not aware, all vehicles have "lock-up" torque converters that reduce engine speed by about 200 rpm's, but only in the higher gears, only above around 35 to 40 mph, and only when the engine is warmed up. That might explain why you see a slight difference in engine speed at different times. The instrument cluster is the most complicated computer on Ford vehicles, but it does not know where the tachometer pointer is. It only knows how to pulse the gauge's coils to place the pointer where it wants it to be. If you see the pointer at a specific position when the ignition switch is on, that is where it is supposed to be. The only other way it can intermittently be in the wrong position is if the pointer were to be physically removed, then glued back on differently in relation to the armature shaft.

Hi Rivermikerat, Sorry for butting in. If this explains the problem, it will save you chasing a non-existent problem.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 2:54 PM

Please login or register to post a reply.

Recommended Guides