Cruise control components

jclars

Registered User
Hi All,

Been awhile since I posted, just having fun with the F100/SC! Been running great! The project attracts a lot of attention. Still haven't put the hood on the truck as the SC engine is a real eye catcher.

Decided to put the CC back together and thought all I needed was to install the vacuum cut-out switch. Got it in place (yellow button depressed when brake is off, correct?).

I have the EVTM, but confused on what specifically makes up the basic CC system on an automatic. What are the electrical components and how does it work? Or maybe more to the point, what might be missing to not make it work?

Is there a way to bench test it without having to actually run it down the road?

Thanks as usual,
John
 
Having recieved great help on my vacuum/boost issue on a different post, I used the knowledge to discover a reversed check valve on the cruise control vacuum line, and so I now have CC.

I was looking for an "on" indicator light on the dash, but I guess this wasn't even available in later years.

If I wanted to add an "on" indicator light, where would I tap in? I tried
the lb/bk wire 151 shown in the EVTM, but it jumpered the horn when I pushed the CC on. I really dont want that kind of indicator!

Anyone done this to their ride?

John
 
Wish i knew where my spare Cruise control module is, even thou i think you said you are using a '89/90 SC setup? which has the cruise control parts inside the ECU?

with the later ('91+) the module itself has a lot more Inputs/outputs(??) then is used. Even has a Throttle position sensor input!

I'm also one of those people that having a light on the dash saying cruise control is set is truly needed. I just think it should be obvious :p

Also wonder if you can use the O/Y (Orange / Yellow) (from my '91 EVTM) wire that goes to the Solenoid that is suppose to be Positive
 
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I guess I would take either at this point. I know my 2004 F150 simply has one light to indicate on, and I think it is upon engaging. Our newer Explorer has both on light, and then upon engaging, a speed indicator. Now wouldn't that be nice!
 
Pressing the 'on' button on the steering wheel, while the engine is running and vehicle speed exceeds 25mph, lights the main cc circuits. CC stays on until you either press 'off' or turn off the key. That's the circuit I would tap into.

According to my '90 EVTM:

C134 - DK BL/W - secondary junction block

-- Behind L/H side of I/P, right hand side of steering column, on secondary junction block term 12.

Alternatively, you can probe the cc's servo motor: GY/BK; O/Y; W/PK.

Note that pins 51, 11 & 35 on the EEC are involved, but I would use them only for reference :)
 
So I need to be cruising down the road with my probe light attached to verify, or will it show on at idle? Just wont engage?

Is the secondary junction the one by the LH kick panel (not the fuse block)? I have moved them around a bit in the remodel...

Thanks,
John
 
I can tap 'On' at rest, and then use 'Set' at speeds above 25 to engage.

The block in question was on the steering column as noted...and may well be the multi-connector that is frequently referenced when talking about replacing the ignition switch (not the key/lock cylinder).
 
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I would definitely work at the power wires for the servo in the inner fender. The cruise control signal wires from the steering wheel are actually the SAME wires that honk the horn. The EEC monitors the voltage on those wires to decide if you are trying to engage CC or not.

Certain combinations of button presses will sometimes honk the horn as well. Fun stuff! :p
 
If I havent already revealed my limits with electrics, I at least know when to ask for assistance (having bumbled a little further, but also having learned).

I tapped into each of the servo motor wires Gy/Bk, O/Y, W/Pk with a grounded test light, and travelled about 40 mph while hoping one of them would light it up while pushing the CC "on" button. Of course none of them did this as you probably already knew.

I am thinking this is because they are simply resistance signals, like a fuel sending unit, and maybe I have to jump across a pair of them to get a signal to the light?

You were right about horn honking with signals from the steering harness. I jumped across to a ground from the blue wire coming out of the CC and when I punched the CC "on" button, got a horn signal. Not exactly what I want.

Any more ideas? This is becoming more of a challenge than a necessity at this point...

Thanks,
John L.
 
What gauge are those wires?

If there is enough current to shuttle a servo there should be enough current to light a small indicator, I'd think.
 
16 to 18 ga. Should be enough, although I probably ran a 8' lead to the cab in order to see it while driving. I disconnected the plug-in while I performed this test at the male end of the connector. Thus any continuity between the three wires was broken. I am already seeing what my next test is going to be...

John L.
 
Maybe you know, but Ford is notorious for using grounds to make and break circuits. I chased a boost trigger for 3 months before I first learned this, way back when...

The circuit needs to be monitored when in place...don't assume hot at a connector when the circuit is open.
 
16 to 18 ga. Should be enough, although I probably ran a 8' lead to the cab in order to see it while driving. I disconnected the plug-in while I performed this test at the male end of the connector. Thus any continuity between the three wires was broken. I am already seeing what my next test is going to be...

John L.

I would backprobe the connector with long hatpins if you can. Also, consider using an LED test light so it doesn't take as much load.
 
I would backprobe the connector with long hatpins if you can. Also, consider using an LED test light so it doesn't take as much load.

I carefully pierce the sheath with a straight pin, then attach a lead, being sure to seal the puncture w/silicone adhesive when done. That, or find another harness I can sacrifice and patch in - I've done this for TPS testing on cars w/mandated adjustment.
 
Thanks to both suggestions. It may be a couple of days before I can take it on another test run. I may be able to insert pins into the back of the connector plug as well, without disturbing the wire sheathing.

Another question that I have in the mean time: Did the 89 automatics have the brake cut-off switch as well as the vacuum cut-off? Or just the vacuum switch? Seems pretty fail safe in and of itself.

John
 
You mean the electrical brake cut-off? The vacuum switch is also brake operated. But I recall discussions about both.

John L.
 
I don't really recall a separate switch. Still, if you step on the brake, the EEC quits trying to accelerate until you hit "RESUME". I wonder if it simply monitors feedback at the CC servo itself and shuts off when it sees the servo move in a way consistent with a vacuum dump?
 
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