Solved The speedometer & odometer suddenly stopped working in my 1993 Aerostar.

[mmerlinn]

Two hours ago, at 399,500 miles on my 93 Aero, I bought gas. Half hour later my odometer went blank, my speedometer needle went max, and the cruise control quit working. Van runs and drives ok, just no idea of how fast I am going. Even after turning everything off, the needle still stays at max.

Worse yet, I expected to roll over to 400,000 miles on the odometer in 3 days, but now, unless I quickly find the problem, that will not happen.

Anyone have any ideas of where I can look? I suspect it is somewhere in the speedometer circuits, but I have no idea where, nor how to find out.

 

[BrooklynBay]

Did you check the fuses?

 

[mmerlinn]

Nope.

Which fuse would it be? Or where do I find a wiring diagram to find out?

BTW, all other gauges work fine.

 

[BrooklynBay]

Do you have the owner's manual? The fuse box is under the driver's side of the dashboard by the kick panel.

 

[mmerlinn]

No owner's manual and have replaced other fuses before. It is just a question of exactly which one to look for.

 

[BrooklynBay]

The 1993 Ford Aerostar fuse block diagram was taken from my Ford software.

 

[mmerlinn]

Thanks for the diagram. As it turns out, this cannot be a fuse problem as the problem disappeared without me doing anything.

When I went to work this morning the needle was still pegged at max before I turned the key on. When I turned the key on, the odometer was working, but the needle did not move. 500 feet down the road the speedometer started working again. No more problems at all today.

It looks like all I lost was about 12 miles on the odometer. However, if this happens once, it will happen again, so there is no way I can say the problem is solved. I did nothing to solve it.

 

[BrooklynBay]

Remove the kick panal on the front passenger's side to obtain access to the PSOM module. Unplug it, clean the contacts, add antioxidant or tune up grease to the connections, then plug it back in. It might be a good idea to do the same thing with the connections on the gauge cluster, and the VSS on the top of the rear differential.

 

[Jose A.]

I think it might be the Vehicle Speed Sensor (VSS) at the diferential / rear axle.

 

[mmerlinn]

SOLVED!!!

I finally figured out what the problem was.

If the ignition switch does not completely return to the drive position after starting, then the circuits involved will remain disconnected, so no odometer, speedometer, etc. I can manually cause this problem to return at any time, so I know that I did indeed find the problem.

Sucks that it took me over 3 years and a different 93 Aerostar to finally solve this problem.

 

[BrooklynBay]

Thanks for the update. Your thread is now marked as solved.

 

[Adam_tinkerer]

From what I've heard, the odo resets to 300K again instead of 400. My '95 made it to 391K, but a likely burnt valve and massive oil leak kept it from going much farther!

 

[mmerlinn]

From what I've heard, the odo resets to 300K again instead of 400.

What you have heard is BOTH correct AND incorrect!

Early Aerostars, like 1986 vintage, had an odometer that rolled back to 100,000.0 miles after reaching 199,999.9 miles.

Later Aerostars, like 1993 vintage, had an odometer that rolled back to 300,000.0 miles after reaching 399,999.9 miles.

I don't know when the change was between them. Nor do I know whether Ford ever fixed the issue in later vehicles.

I just know I had a 1986 that rolled over as above, now have a 1993 that rolled over as above, and now have another 1993 with 273,000 miles that I expect to watch roll over at 400,000.

 

[RangerX]

Do Aerostars have a digital odometer? My 93 Ranger has a mechanical one, just wondering...

 

[mmerlinn]

Do Aerostars have a digital odometer? My 93 Ranger has a mechanical one, just wondering...

All three of my Aeros had/have digital odometers. No idea whether all Aeros had them.

However, my 1986 Aero had a digital speedometer, while both of my 1993's have analog speedometers.