Haven't been here is a while because the Aero has been behaving... until yesterday. It's a 95 shorty 2WD 3.0L with about 225,000 miles (365,000 kilometers). The instrument cluster has needle-type gauges (not a digital dash), but a digital LCD odometer.

When I started the van yesterday, I noticed the odometer was blinking on and off, and the speedo needle was "twitching" in time to the odo blinks. The van was not moving at the time. When the odo was on, it sometimes diplayed all 8's, like a normal startup and sometimes displayed the current mileage. The blinking and twitching was at a regular beat, not erratic like a poor connection. All the other gauges work fine.

As I started driving, the speedo moved up to indicate the speed I was driving, but it was still twitching. I shut the engine off and restarted it after about 5 seconds - the odo was blank and the needle was dead at zero. I shut it off for a few minutes and when I restarted, things were blinking and twitching again. After a couple of minutes of driving, they went dead again. Since then, sometimes they blink/twitch, sometimes they are dead. I have not noticed normal function since.

I'm having a bad vehicle week. When the speedo starting acting up I was pulling my utility trailer to pick up a wrecker engine for my son's car (cracked head), then I had to leave the van and trailer for my wife to drive home because her car blew a brake line on the way to work. We only have three vehicles and this is the only one that both moves and stops!

After dropping my son off at work this morning, I noticed the engine seems to rev a little higher at "country road" speeds (50 mph), like the torque converter clutch is not locking up. This van has never had transmission trouble & I have changed the fluid & filter a couple of times, but it's due again.

I have had the instrument cluster out before, and had great difficulty disconnected the speedo cable. I would normally suspect a bad or dry cable if the needle twitches, but it was doing that when the van was stopped. Due to my other vehicle woes I haven't had any time to look at this, but I need to take the van out of town this weekend, and I am concerned about highway driving if the TCC isn't locking up (high gas consumption and an overheated transmission).

I searched and found threads about the problems F-150's and Expeditions have with blinking odometers, but in those cases the speedo still works, or the speedo isn't cable-driven.

Anybody had problems like this and can help me narrow my focus? I have had a few electrical gremlins lately: tempermental camper connector feed so my left trailer brake/turn light works inconsistently, door ajar light glowing dimly even though all doors are closed (once only - this morning), and a couple of other things I can't recall right now. I have had a leaky windshield for a couple of years now (a poor rust repair at the top) and figured this might account for the electrical glitches, but it hasn't rained for a couple of days.

Any advice will be greatly appreciated.

Cheers,
Eric

 

i had a similar problem, no speedo, odo, and also my interior lights would not wokr, and the radio woudl not work, and the trans would not shift right.
I found a thread on here and it led me to the wire going thru the sunvisors to the lights in the vanitiy mirrors inside the visors, the insulation was cracked, and shorted them out, and blew the 15amp fuse, that fuse controls all of the above.

 

check fuse #8 and #17, power to PSOM

your analog speedo needle is electronically driven by the PSOM
likely failure is speed sensor on top of rear differential which sends an electronic pulse signal to PSOM via wiring, magnetic pickup driven by steel notched tone wheel mounted on ring gear back...sensor commonly fails or wiring/plug connector damaged/corroded...may also be damaged/broken tone ring

if speed sensor circuit fails, transmission may not shift into 4th OD or TC lockup also no cruise control

or you have a failing PSOM module or cracked solder joints on PSOM circuit board=common failure

Programmable Speedometer/Odometer Module
The Programmable Speedometer/Odometer Module (PSOM) includes the Speedometer, the Odometer, and the Trip Odometer, which are all electronically controlled by a microprocessor. The microprocessor receives a speed signal input from the Differential Speed Sensor (DSS), and uses a programmed conversion constant to convert the signal to the standard 8000 pulses-per-mile speed signal output.

For Programmable Speedometer/Odometer Module diagnosis, refer to Section 13-02B of the Service Manual.


Programmable Speedometer/Odometer (PSOM)

The programmable electric analog speedometer receives its input from the anti-lock brake sensor. The liquid crystal display (LCD) odometer is a combination trip odometer and total odometer. The total odometer is normally displayed. To see the trip odometer, press and release the SELECT button on the upper right side of the speedometer. To zero out the trip odometer, press and release the RESET button on the upper left side of the speedometer while the trip odometer is displayed. If the trip odometer is displayed, press and release the SELECT button to return the display to the total odometer value. The speedometer, containing the trip odometer and total mileage odometer, is serviceable only as an instrument cluster assembly. Refer to «Section 13-01B» for ordering instructions.

NOTE:
Before ordering a service cluster, contact the instrument cluster technical hotline for diagnostic and system troubleshooting assistance. The hotline phone number is 1-800-523-7763.

The speedometer is also used to provide a speed signal for correct operation of the vehicle's Powertrain Control Module (PCM), electronic transmission and speed control (if so equipped). Because of this, it is VERY IMPORTANT to change the speedometer's internal conversion constant if the size of tires, or the rear axle and ring gear on the vehicle are changed. Changing the conversion constant to the proper value when the tires, or the rear axle and ring gear are changed will also make sure that the speedometer retains the original factory-set accuracy. The conversion constant can only be changed six times once the vehicle leaves the factory.

 

Thanks for the information.

I'm thinking (hoping) it's a blown fuse. All the items Nick listed that are on that circuit are acting up:
1) The speedo/odo (and thereby the transmission shifting)
2) I just called my wife at work (she has the van today) and she told me the interior lights are dead. The dim door ajar light comes into play here, too.
3) The radio has worked sporadically during the past couple of years. It's an aftermarket unit & I figured it got wet & was shorted out due to the leaky windshield.

Unfortunately I probably have to wait until my wife gets home (9:30 tonight) before I can take a look at it. And of course, if the fuse is blown, where is the short???

Nick: since you traced the circuit before, do you remember the wire color and might you have any idea where I can clip it (if necessary) to isolate the non-essentials until I have time to trace everything out?

96_4WD: Thanks for the info. It will help me out if it does not turn out to be a fuse. The only thing that doesn't add up is that I know there is a speedo cable to the back of the cluster - I have had the cluster out a couple of times and had a heckuva time trying to disconnect it. To me, the speedo behaves like an electric driven unit (twitching while the van is not moving), but there is definitely a cable there. Might it make a difference that this a Canadian van with a metric cluster?

Cheers,
Eric

 

i think the wire color is black, but pull down ur visors, and the headliner and they're right there.

 

I had that same wild thing with my 95 AWD. I picked up a used speedometer from the junk yard and it worked perfect. Dealer price was $300 junk yard $10 if you pull it yourself.

 

Fixed it!!!!

Fuse #8 was blown. When I replaced it all was working as it should, so I started fiddling with things on that circuit. When I opened the front passenger door, the interior light dimmed (I had turned it on from the headlight ****). Closed the door quickly and the light went to full bright. Next time I opened it all was fine. When I started wiggling the pin switch, the interior light dimmed again then the fuse blew.

So I pulled out the switch and voila... the green/yellow wire had pulled out of the plug and the bare end was hanging in the breeze. >SNIP< >TAPE< and all is now fine. Since this van has morphed from family hauler to cargo/work truck, I don't really want the interior lights on whenever a door is open (I often take out the bulbs).

Thank you very much, folks! I am sure I would have spent hours troubleshooting this one. 5 minutes troubleshooting, 10 minutes fixing (the kick panel is a little tricky to get off), and 2 fuses were all it cost me.

FTE rules!

Cheers,
Eric

 

glad to hear you fixed it, these vans have freakin weird wiring, as in all the random crap they cram onto a circuit