Speedometer Reading Way Off?

robo44 · 11-13-2018, 10:30 AM

Hi
I just picked up our new 2019 FR3 33DS a few days ago. On the drive home from the dealer (about 400 miles of travel) I noticed that between my GPS speed reading and the Speedometer on the coach differs by 10 MPH.

The Coach stated Im traveling 60 MPH while the GPS says 50 MPH. GPS is pretty accurate, and while I know there may be some slight differences 10 MPH seems excessive.

How can this be? This is a brand new coach

Has anyone else seen or experienced this? I definitely will take or discuss with Ford as I would assume it is a warranty item that needs to be fixed or repair.

kenandterry · 11-13-2018, 10:40 AM

I agree that 10mph seems a little excessive......GPS units are really pretty damned accurate considering everything about their tracking abilities.

However, if you’re reading 60 on the speedo and the GPS says 50, you shouldn’t ever get a speeding ticket

formerFR · 11-13-2018, 10:55 AM

time it between milepost - if you hit a mile in 1 minute, then you know you're traveling
60 miles per hour

kenandterry · 11-13-2018, 10:58 AM

.......but he might be speeding before he gets to that next milepost.

robo44 · 11-13-2018, 11:39 AM

True, speeding tickets aside, or wondering why a caravan of cars are honking their horns at me when I am "driving the speed limit" has me confused Service adviser just told me over the phone I was probably looking at KPH and not MPH. After 50 years of Driving I think I know the difference.

**Bama Rambler** · 11-13-2018, 12:18 PM

It's likely that the chassis was programmed for the wrong sized tires. Should be an easy fix to reprogram it to the correct tire size.

GoneSouth10 · 11-13-2018, 12:25 PM

Also, you may want to point out to that service rep (trying not to insult his intelligence the way he insulted yours, of course) that if you were looking at the KPH numbers, your speedometer would read "80" (assuming a true speed per the GPS at 50 MPH). I guess it's a lot easier to blame someone else than fix the probable problem (See Bama Rambler's post, which would be my first guess for a discrepancy that large).
Good luck!

Boomerweps · 11-13-2018, 12:40 PM

Most likely cause is the wrong plastic speedometer gear in the transmission for your tire and axle ratio combination. Being a new Ford chassis, Ford should cover it under warranty. Your salesman has used car salesmanitis also known as anal-cranial inversion.

GoneSouth10 · 11-13-2018, 12:54 PM

Quote:

Originally Posted by Boomerweps

Most likely cause is the wrong plastic speedometer gear in the transmission for your tire and axle ratio combination.

I'm assuming that the speedo is part of a fly-by-wire system in a 2019 chassis, so it should just be a reprogramming issue, per Bama Rambler.

That said, your diagnosis of the service rep's unfortunate condition was spot on!!

Bluepill · 11-13-2018, 03:12 PM

A Big problem is that your ODOMETER may be racking up too many miles. An error of 20% high is a lot.

n0ms · 11-13-2018, 03:25 PM

Quote:

Originally Posted by formerFR

time it between milepost - if you hit a mile in 1 minute, then you know you're traveling
60 miles per hour

This is the correct test. Reset the trip odometer also at the start. Math doesn’t lie .

cariboo camper · 11-13-2018, 04:10 PM

Quote:

Originally Posted by robo44

Hi
I just picked up our new 2019 FR3 33DS a few days ago. On the drive home from the dealer (about 400 miles of travel) I noticed that between my GPS speed reading and the Speedometer on the coach differs by 10 MPH.

The Coach stated Im traveling 60 MPH while the GPS says 50 MPH. GPS is pretty accurate, and while I know there may be some slight differences 10 MPH seems excessive.

How can this be? This is a brand new coach

Has anyone else seen or experienced this? I definitely will take or discuss with Ford as I would assume it is a warranty item that needs to be fixed or repair.

My 2917 FR3 DS28 was about 4 MPH lower reading when purchased new. I could fix it I suppose by putting in different gears in speedo cable but I have a GPS so I just learned to live with it.
I would agree though 10 MPH is way out there.

bubbles · 11-13-2018, 04:36 PM

My GT indicates 3 mph higher than my GPS at an indicated 65 mph. My previous MH with an identical chassis (different manufacturer) indicated speed always agreed with my GPS.

Scrapper · 11-13-2018, 05:40 PM

I once had a county deputy friend check my speed with his radar, my speedo read 3mph over while my gps was the same as the radar.

robo44 · 11-14-2018, 06:09 AM

Appreciate all the good (and funny) responses. I have an appointment to have Ford take a look. It sure sounds like a programming issue but we shall see and I will report back

pdqparalegal1 · 11-14-2018, 10:02 AM

Quote:

Originally Posted by robo44

True, speeding tickets aside, or wondering why a caravan of cars are honking their horns at me when I am "driving the speed limit" has me confused Service adviser just told me over the phone I was probably looking at KPH and not MPH. After 50 years of Driving I think I know the difference.

My Ford PU had KPH on display untill I scrolled through the menu and changed it. Pretty easy to miss.

robo44 · 11-14-2018, 10:17 AM

Mine is not a digital screen big numbers with the orange hand old school speedometer

**Bama Rambler** · 11-14-2018, 10:32 AM

Even if it looks like an old style analog speedometer it's still electronic and controlled by the ECM. Look at the speedo and if it moves during the self test when you turn the key on, it's electronic.

Chuck_S · 11-14-2018, 11:00 AM

The Ford chassis instruments are digital and controlled via the ECU. Ford chassis should have a firmware setting for the axle ratio if has the BCM module. I doubt the RV dealer has a clue how to access it but Ford can. And can anyone with a laptop and free Forscan software in it and a connector to the ODB2 port.

You should be able to access the "As Built" data with your vehicle VIN at motorcraftservice.com. Address 746-45-01 contains the axle hexadecimal data in the first data sequence. Mine is 746-45-01 x14B xxxx xxxx (where x can be anything). This indicates a 3.31 axle ratio. This is valid for my Expedition. I don't have all the codes for the larger trucks though but will bet someone has them.

And, of course, different tire diameters will affect the effective axle ratio,

-- Chuck

GoneSouth10 · 11-14-2018, 11:01 AM

Quote:

Originally Posted by pdqparalegal1

My Ford PU had KPH on display untill I scrolled through the menu and changed it. Pretty easy to miss.

Not to belabor the point, but the ratio of MPH to KPH is roughly 5/8 (1 MPH = 1.60934 KPH). Meaning if you're travelling at 50 MPH and your speedo is inadvertently set for "KPH", it will read 80 (whether digital or analog). Hopefully everyone who is on this forum can readily ascertain the difference, particularly in a motorhome/hauling a trailer, between travelling at 50 MPH versus 80 MPH by just looking out the window . . .
This is a quick fix on the ECM.

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