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The most common cause of the cruise not working is a bad clock-spring connector. Is the Air Bag warning light on? Does the horn work from the pad on the steering wheel?
That's good to hear. Now we know the problem is somewhere else.
You might already know this, but Ford issued a recall for the speed control deactivation switch. Has that repair been done to your truck? If yes, then you'll need to remove the driver's air bag module so we can start testing the circuit from the switches. If you'd like, I could upload the circuit diagram so we could both follow it along.
Yes, you should. The recall I was referring to is NHTSA's 09V399000 (Ford's 09S09) and pertains, among other vehicles, to all Ford and Super Duty trucks from 1999 to 2003 - you can click here to read the actual recall notice.
I'd be more than glad to continue our diagnosis if necessary after the recall concern has been addressed.
Well then I guess that means your VIN was not included in the recall.
Regarding the diagnostic procedures, first thing to do would be to remove the driver's air bag squib from the steering wheel so we could then gain access to the wiring going to the cruise switches. Is that something you're comfortable doing and have the tools to do it with?
Also, how about that wiring diagram, would you like me to upload it so we can follow along, or would you rather work off my instructions?
OK. The squib is what houses and contains all the things that will inflate the air bag. The air bag will come out of the squib when activated.
You will need basic hand tools and a good multimeter. I have attached the diagram in case you'd like to take a preliminary look at it.
I'm usually online weekdays from 2 to 8PM. Look forward to working with you.
My apologies. We just had a massive power outage.
Next step would be to use your meter to test continuity on the cruise switches, or, as I would prefer, you could leave the airbag squib out and re-connect the battery so we could test actual voltages at the switches. How about it?
It's the Caribbean, so they call it Atlantic Standard Time.
The only thing you need to remove for now is the airbag squib. With that out of the way, the switches and wiring should be accessible for testing.
OK. Turn the ignition switch on and check to see if there is voltage at the Dark Blue wire coming to the part of the switch that turns it ON and OFF (right side of the diagram - same circuit feeds the horn switch). If there is power there, turn CC on and check for power at the Light Blue/Black wire (left side of the diagram - circuit goes to the powertrain control module (PCM). Are those circuits OK?
You assume correctly, my dear sir (sorry I was just talking to my neighbor from the UK... )
It's actually quite common for these switches to fail after a few years. You can find new switches online for less than $100.
OK. Does that mean there's now power at the Light Blue/Black wire (left side of the diagram) with the cruise switch turned on and still the cruise won't work? If so, then there is more than just a bad switch and we need to keep testing.
The diagram shows power coming into the switch from the right side via the Dark Blue wire. When the switch is turned ON, the circuit closes and sends power through to the left side (Light Blue/Black wire). That means that either the replacement switch is not good or the clock spring is bad. Can you remove and test the switch for continuity to confirm it is good?
That's OK. I'm usually on weekdays from 2 to 8 PM EST.
The reason I asked to check the replacement switch is because it is very rare to see a clock spring that is OK for the horn and airbag circuits, but not for the cruise control - as a matter of fact, I've never seen one do that.
That's interesting. So it seems that the cruise did work after all, albeit just for that one time. That sounds like there is an intermittent open circuit somewhere between the switch and the PCM; however, the fact that the light did not come on when the switch was turned ON, tells me we still don't have sufficient data to rule out the switch or the clock spring as being the culprits.
I don't know how familiar you are diagnosing intermittent circuit faults, but it can be a major headache. Recognizing they had that kind of problem, Ford came out with what they call "wiggle tests"; meaning you grab a hold of the suspected wiring harness and connector and shake the heck out of it to see if the issue can be duplicated. Thing is we have several connectors involved in this circuit.
One thing that could make our task a lot easier would be if you could plug in a NGS or equivalent scan tool that would show the PIDs related to this issue. Is there anyway you could get your hands on one of those? If not, there's just those "wiggle tests"...
Not unless the check engine light is on and there a codes set. You see, the auto parts stores call those things "scan tools" for marketing purposes, but they're are nothing but code readers only good for retrieving and erasing codes. The NGS scan tool I'm talking about is what we used at the Ford dealer and would be the best option; however, there are aftermarket companies like SnapOn, OTC, Autel, and more that make scan tools that can almost duplicate NGS functionality.
You see, the way manufacturers have set things up, you need very expensive tools that require very expensive training to diagnose most of the computer-controlled systems on the vehicles they sell - they have used loop holes in the Clean Air Act to basically create a monopoly where you have to take your vehicle to them in order to get it fixed. It sucks...
Sorry for the rant, didn't mean to sound like Bernie Sanders ;-)
So it looks like its back to the wiggle...
Do I leave the air bag out? Yes
Wiggle while I drive? I wouldn't recommend doing that. The cruise should turn on with the engine running and the truck not moving, then set once the truck is moving at over 40 MPH
Should the cruise light come on when I touch the button, or do I have to hold the button while I hit set? The sequence should be; Turn switch on; reach desired speed; set cruise (light comes on)
Or.....would I likely just solve the problem if I installed a new clockspring? That's impossible to know at this point. The intermittent open could be anywhere in the circuit, the clockspring being just one part of that circuit.
I understand. I wish there was something more I could contribute other than what I've already have. It all boils down to having the proper scan tool...
At this point, it looks like I have nothing else to contribute. I'll opt out and reopen your request to the field in case another expert wants to chime in. Please do not reply until another expert responds or the site will cycle the request back to me.
Welcome, I'm Chris (aka Moose).
Different tech here, would you like me to try and help?
Super, is this still the only issue we are addressing "1999 Ford F350 Diesel cruse control doesn't work, light doesnt come on."
Thanks, ***** ***** how Ford wants this concern diagnosed. https://dl.dropboxusercontent.com/u/90220402/speedcontrol..pdf
If you would prefer me go through step that needs to be done I can do that it will just take longer.
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