I have a 2000 f350 srw 7.3. 131,000 mi . Today several problems started.
1) The speedometer quit working
2) the overdrive switch started blinking off
3) The air conditioner will continue to run with the key off and in my pocket. I can turn it off at the control though.

All of these problems started at the same time , Any info would be greatly appreciated. Thanks Ron

 

Not really shure what you got going on but this may spark some additional posts for you.

1) fuse
2) P-codes being sent (mine was a transmission issue when it was blinking)
3) sounds like a short

hope this can get you going....

 

Never heard of the AC issue. For the other 2, I'd check the VSS on the rear diff. (NAPA calls it an ABS sensor). It's held on with a 10 mm bolt. Remove and clean it to see if you notice any difference. The part is less than $30 at NAPA, so swapping it out for a new one might also be an option. It's the most common issue for the speedo, and can account for the OD light too.

 

Today it started a beeping noise from under the dash. I checked fuses and found no problems. Any ideas Thanks

 

I agree on the abs sensor being bad. I had a 96 f150 and one today on my way to work the speedometer quit, trans wouldnt shift[auto],and it was the abs sensor . got it to work ,put it on the lift and swapped the switch in just a few minutes.Be sure to clean around the switch before removing it just to keep dirt out of the rearend. some have had luck cleaning the sensor others have not. when i replaced mine it was actually cheaper at the ford dealer than the other auto parts stores.but that was 6 years ago

 

the beeping noice you are getting from under the dash is because one of the idiot lights on the intrument cluster is out.. what ever problem you are having would of caused 1 of the idiot lights to come on but being the bulb is burnt out its beeping to notify you... happen to me last week with a airbag problem.. switched out the light bulb and the beeping stopped and the idiot light came back on

 

good job on the beeping i read that in the book but i had forgotten. ford actually trying to have a 2nd level of warning

 

After reviewing some of the threads another culprit may be a leaking windshield. I have been finding water on the drivers side mat.

Where does this lead? I went to a auto zone to have codes pulled and nothing showed up because the engine light was not on. Could it be a GEM?

I am not sure what might next step is after getting the windshield fixed.

The problems again are
1) no speedometer
2) blinking light on overdrive switch
3) a/c keeps running even with truck off and key in hand,has to be turned off at selector


Thanks Ron

 

The sensor being broken in the rear diff will cause the speedometer to show zero which would cause your auto-tranny to be unhappy there by showing a fault/blinking overdrive light.

There is the possibility that your ac/heater blower is continuing to run because of a ground loop (or whatever the proper term is). Check the major grounding bolts and screws under your dash. The loop will cause random power to go all over place. I once ended up with my dashlights blinking, drivers side window going down, and radio clicking on and off all because of a single grounding bolt being loose. I would have been funny accept for the part about driving through a snow storm with the drivers side window trying to go down.

The leaking windshield could also be the cause of the ground loop but not as likely as a loose screw. I've had a leaky windshield for over 3 years and haven't had an electronics problem. I'm still expecting to one day step on the carpet and be knocked back out of the vehicle by a heavy shock.

The more I say ground loop the more I like the phrase. Too bad I know someone's going to jump in and correct me.

I wish you luck with your search. Electrical gremlins are the most irritating problems.

 

I'd met a fellow once who told me about replacing his PCM twice and some other parts before finally discovering his windsheild was leaking on the drivers side, getting water down in the PCM. Since you're seeing water, it'd be a place to investigate. Hope it turns out an easy fix. Good luck!

 

Thanks for all the input .I replaced the sensor on the rear diff and I still have the same problems . Any ideas what I should do next. The funny thing is the speedometer went to 5mph and then quit again after I replaced the sensor.

 

what did the old sensor look like? did it have a lot of metal fuzz on it, if so that may be the problem, not likely but its a possibility if there is huge amounts of wear metal floating around

 

very little fuzz