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Cruise Control Quit Working.

fatherdoug

Tonto Papadapolous
I took the '78 for a drive yesterday, and couldn't get the cruise to work. The last time I used it, I had to mash on the "set" button pretty hard to get the cruise to work. I installed a new cruise/horn pad from a Gen 7 truck which has worked flawlessly for the last 2 or 3 years. The fuse for the accessory circuit, which powers the cruise, is good. I will check vacuum lines and reservoirs to make sure they are good. I guess the only other possibility is the servo(hard to find a replacement), the amplifier(rebuilt available), or the speed sensor(don't know about availability). And yes, the horn works, also. Another possibility is the connections to the ring on the steering wheel.(Clockspring?)

I've been looking at the vacuum and electrical troubleshooting manual that Duncan posted.(Thank you!)

Any thoughts or experience?

I forgot to state this is a factory installed setup. Everything is original except the Gen 7 horn pad.
 

fatherdoug

Tonto Papadapolous
I checked all the vacuum lines and both canisters. I'm not seeing any leaks. I haven't checked any ohm readings yet. I pulled the steering wheel and found nothing obviously wrong with the wiring. I also pulled and reseated the electrical plug for the cruise control under the horn pad.
 

fatherdoug

Tonto Papadapolous
I found a package deal NOS servo/amplifier for $100. Waiting for it to arrive. Hope that solves the problem. Never did do any electrical troubleshooting since ions don't like me...
 

fatherdoug

Tonto Papadapolous
Replacing the vacuum amplifier made no difference. My oil pressure gauge no longer works, so I will have to pull the cluster out again to see what I screwed up. :headbang:
 

fatherdoug

Tonto Papadapolous
I replaced the servo with an NOS out of a 1972 Lincoln with 460(exact same setup). The chain from the servo was too long and was rubber coated. The rubber coating did not fit through the bakelite receiver on the carburetor, but a heat gun took care of that problem. Also the chain had to be shortened up so it wasn't dangling on the manifold. It worked great......twice, and then stopped working. Now I'm thinking it might be the horn pad, which was an NOS about 3 years ago from a Gen 7 pickup.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
BOO switch (I'd surely expect it to have one)?


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....the servo(hard to find a replacement), the amplifier(rebuilt available), or the speed sensor(don't know about availability)......

Every now and then I tinker on an experimental project and need parts, and I hit the local upull for them. If you get in a bind, I can keep my eyes out for something you may need; my cost is yours as would be USPS shipping (UPS sux), you do the research on interchanges between vehicle models and bear in mind, although they post the VIN, the lot doesn't inventory details about the features/options/engines/etc etc cars. I think you and most anyone would be amazed at the low prices (look in the linky for them).

Linky:.....http://pullandsave.com/ and I visit the north store.
 
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fatherdoug

Tonto Papadapolous
Thank you, Bill. The brake pedal cancels the cruise, so I'm assuming it does. If I remember, the cruise setup(regarding the brake switch) for this truck was specific to trucks with cruise, and may be hard to find?
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
I'd expect a wear item like a switch would be available for many decades.
 

fatherdoug

Tonto Papadapolous
The problem seems to be related to brakes/electrical. I have an older brake controller for a trailer with an indicator light that goes from green to yellow as the trailer brakes are applied. I noticed this morning that when the ignition switch was in the on position,
the indicator light was yellow without pressing the brakes, and that the indicator light would go back to green when the ignition switch was turned off.

I also noticed that I had no brake lights when the pedal was pressed. So, the problem appears to be electrical/brake related. I HATE electrical problems.

I ordered a NOS brake switch for cruise and will replace that. I did disconnect the trailer brake controller, but it made no difference.
 

BKW

Ford Parts Guru
The problem seems to be related to brakes/electrical. I have an older brake controller for a trailer with an indicator light that goes from green to yellow as the trailer brakes are applied. I noticed this morning that when the ignition switch was in the on position,
the indicator light was yellow without pressing the brakes, and that the indicator light would go back to green when the ignition switch was turned off.

I also noticed that I had no brake lights when the pedal was pressed. So, the problem appears to be electrical/brake related. I HATE electrical problems.

I ordered a NOS brake switch for cruise [confused] and will replace that. .
No such thing.
1978: There are two different brake (stop lamp) switches, with or without Speed Control makes no difference.

Before (D2TZ-13480-B / Motorcraft SW-691-A) or from (D8TZ-13480-A / Motorcraft SW-1511) serial number CG0,001 does.

The Speed Control switch within the horn pad was available separately. There are two different types.

1978/81: D8AZ-9C888-A = Off-On-Set Accel-Coast

1980/87: EOTZ-9C888-A = Off-On-Resume Set Accel-Coast
 
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CowboyBilly9Mile

Charter Member
7,118
442
USA
Results?
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Troubleshooting today. No results yet. It's only 93, and I'm sweating beer faster than I can drink it.

I'd pull it in the garage, close the door, fire up the AC, and git-r-done!
 

fatherdoug

Tonto Papadapolous
97 now. Garage is a storage shed........ Problem appears to have been the Turn Signal Switch. I got a new one for $132.00 from CG Early Ford Parts, compared to $170 from other places. The TSS solved all the previous lighting problems, except the wire colors on the new switch don't match the wire colors on the old switch. I think I got the turn signal wires mixed up with the hazard wires. Life is better, thanks to the MASTER.....:D
 

fatherdoug

Tonto Papadapolous
Cruise Control works now, also. The entire problem, lights, brake lights, cruise control was solved by replacing the Turn Signal Switch.

I forgot to put the horseshoe-shaped keeper back in the connector. That is why the turn signals and flashers were not acting right. It had pushed some of the pins back into the connector, so they weren't making contact.
 
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