Diagnosing Speed Control

[ckuske]

I've moved onto my next item:  Speed Control not working

It was non-operational when I bought the truck back (meaning it never engages/turns on)  I've printed out the FSM section, and have started to run tests.

I'm at Page 37-01-3 of the FSM.  The first test (Test for 12 Volts when On Button Pressed) is passing.  But, that's where my luck ends.

Step 2 of checking for 0-1 Ohms when pressing the OFF button is failing.  When my steering wheel is locked, it seems like the circuit is open.  If I put the truck in Run and the steering wheel unlocks, I get a 100-200 Ohms.   If I turn the wheel about 1/4 turn, the ohms go down to 40-60, but certainly never to 0-1 Ohms. I'm guessing the back side of the steering wheel isn't making good contact with the brushes on the turn signal switch?

The horn is working in different wheel positions, that's never been a problem.

Besides checking the brushes (the turn signal switch is brand new, put it about a year ago with very little use), what else should I be looking at if turning the wheel seems to alter the resistance readings?

[ckuske]

Here are a few pictures of the steering wheel and the turn signal switch:

[Gary Lewis]

It seems like you have a grounding problem.  Can you show us a pic of the way your steering wheel is wired?

[ckuske]

Sure thing - the yellow and blue wires go onto the two ears inside the steering wheel, and the ground wire fits inside one of the bolt holes that are used to pull the wheel.  It seems that is normal after doing some reading - it seemed questionable at first...

[Gary Lewis]

Yes, that is normal.  But if the ground isn't good you'll have lots of odd problems.  Big Blue's horn worked with the key off but not on at one point.  Turned out that the speed control was working as the ground for the circuit until it was powered up, but then it wasn't a good enough ground to pull in the relay.

I don't remember what the problem was, but I know others have had problems where the steering column wasn't well grounded.  And that's where I'd recommend you start.  Measure from the column to ground and move the wheel around, as you've done.  If it changes then you aren't well grounded.

[ckuske]

I measured ground from the metal collar on the column (right below the wheel) to a dash attachment point, and it came out to zero ohms.  Like 0.0 ohms which I thought was kind of suspicious - should I not use the dash mounting legs as the other end of the ground test?  

The test said to pick body sheet metal - maybe I take a kick panel off and try there are the ground point?

If all that is OK though, I'm assuming in general the column is grounded but the continuity from the wheel through the column is bad.

Should I pick one of the connection points (aka "ears") on the wheel as one end of this continuity test? (Where the blue/yellow wires attach)

[Gary Lewis]

The only grounding point that really matters to the speed control is where it is grounded.  And according to the schematic that is G703, which is said to be "attached to brace under steering column".  It is depicted on Page 139 in illustration #2.

So I'd check out that ground and do my test from the steering column's flange where your ground clip goes in to G703.  There shouldn't be any bobbles when you move the wheel, pull on it, turn it, etc.

But, G703 should also have a good connection to the body, so check that out as well.  One spot I frequently use is the bracket for the dash just above the emergency brake.  But you may have a grounding problem to the cab.  There's supposed to be a ground from the engine to the firewall near the windshield wiper motor.

[ckuske]

Found G703.  Another ground I never knew existed, because I never took the ECU or Speed Control Amplifier out of the truck even though I stripped the rest of the interior awhile back.  I will try to do some tests tomorrow against this ground, but it looks good.  I tweaked my back a few days ago and even though I am motivated to test all these connections, lying on my back over the transmission hump upside down doesn't feel so great that the moment!  I had some choice words when I was trying to get the connections off the amplifier...

PS - I no idea what that three terminal connector is for.  It must not be used in my truck?

[Gary Lewis]

I don't know that I would say it looks good.  The bracket the eyelet is going down against is painted, so you may not have a ground.  And if it really is connected to the bracket is the bracket connected to the firewall?  And is the firewall connected to the engine?

Ford was very lax with grounds up through '86.  In '87 and later they started adding a lot of grounds.  So our trucks aren't grounded well and there's no redundancy.  If one of those grounds isn't working then lots of problems arise.

As for the back, that sounds painful!  Hope you get some relief.

[ckuske]

True about the paint - I was just happy I was able to find it!  If anyone else has a picture, I'd be curious to see what theirs looks like.  I'm pretty confident things are good with the grounds to the engine.  I know for sure the EEC has a ground to a post on the intake that I redid.  I'll try to trace this one back and see if it's part of the same harness coming through the firewall or is something different.

My back is better each day, once every couple years I get spasms that lock up my lower back and after a few days the muscles relax and I'm back to normal.  It could be worse!

Maybe I'll try to relocate that ground - or even jumper it to somewhere else as a test?  I still think there is a problem when turning the wheel that is separate.  The ohms shouldn't jump around from just turning the wheel.  The copper contacts on the switch look a little worn, but I'm assuming since the back of the wheel rubs on that, it's normal?  Perhaps I should use fine grit sandpaper and sand the disc on the back of the steering wheel?  I'm probably getting ahead of myself - one thing at a time.  But I'm trying to anticipate my next move...

[Gary Lewis]

Glad to see the back is getting better.  I've had a few of those and they are not fun.

I don't understand how the steering shaft is supposed to be grounded.  The factory bearings top and bottom have plastic races and the top one is then set in rubber.  So it can't ground through the bearings.

Perhaps it is supposed to ground through the rag joint to the steering box?  But I'm not convinced the steering box's bearings are a good conductor of electricity.

In any event, we had a discussion about this in the thread entitled Steering Column Ground, and you might want to at least read this post.  In that post there's a pic with three brushes and a description of the purpose for each.  Check to see if the ground one on your column is actually grounded.  Does it change if you move things?

[viven44]

Its been a long time but I had a "lesson learned" when I installed the turn signal switch. There are 2 screws that hold the turn signal switch to the column. I think if you overtighten those screws that will reduce the spring tension BETWEEN the PINS that connect the blue and yellow wire AND the "RACES" on the backside of the wheel... which in turn will affect resistance value depending on wheel position..

[ckuske]

Thanks Gary!  I'm reading up and am gathering things to try.  I'm going to focus on just getting the ohm readings to come out correctly.  I suppose I could even try things just on the wheel itself, and make sure the switches have the right resistance values out to the hub of the steering wheel?

I also stumbled on this post from Ron - is this a real thing?  (I'm guessing so!)

If so, I'm missing a brush according to his picture.. (see my photo above)  If I need it, any ideas where I can get one???

[ckuske]

That is worth a definite shot Vivek, thanks for that!  

[ckuske]

One more note, this blurb from Dennis Carpenter mentions a speed control brush assembly needing to be re-added/connected.  I think the part number contains 9C899, but for the life of me I can't find an example of it that makes any sense.  Do I have a missing link (no pun intended)?

[Gary Lewis]

Chris - Using the verbiage from my post in the Steering Column Ground thread, I think you have all the pins "with the one circled in red being the ground, the one in yellow being power, and the one in blue going to the speed control".

Those match my pic in that post.

[Gary Lewis]

As for 9C899, that is the ground pin, as you can see from this snippet of the illustration:

[ckuske]

Thanks Gary.

I'm feeling better today so I started measuring resistance again.  Same results as yesterday, actually it was a little worse.  I decided to move the turn directional switch out of the way, and take a look at the bearing.  I posted a video here

I'm guessing I should replace the upper bearing, right?  I'm not sure if its related or not, but the wheel has some "jiggle" in it, perhaps the continuity is disrupted.  I need to take the whole upper flange off to replace the bearing, right?

[Gary Lewis]

Chris - If you have a tilt column, as I think you do, then I can't answer your question as Big Blue has a non-tilt column and that's what I've just been into.  But on my column the upper bearing doesn't have anything to do with the grounding of the column.  The bearing has plastic races and is encased in rubber, so there's no chance it'll conduct.

If I were you I'd pull it apart to see what the issue is.  The instructions are on our page at Documentation/Interior/Steering Columns & Steering Wheels.

[ckuske]

Am I confusing lower vs upper?  I would assume the bearing showing in my video with the steering shaft is the "upper" and I think the illustration supports that.  It looks metal to me, and this link for a replacement looks correct.

I guess what I am asking so far for this portion of the adventure is:  Is the play of the steering shaft in the video acceptable?  Should I replace it while I have the column apart again?