Cruise control

[Romel]

Hi Gary,
I am just wondering what mine cruise control problem could be on my 1986 XLT. It does work sort of, when I engage it, it just goes full throttle, when I press coast it eases but after I release it goes wot again. The only thing that comes to my mind is the amplifier unit malfunctioning. Or am I overlooking something? I have changed the buttons on the steering wheel, it is the same.

[Steve83]

No, it's more likely a fault in the servo: either a bad TPS, or (the most-likely) a plugged vacuum vent (usually due to wasps).  Read this whole caption:

[Romel]

My problem is I am located in Europe so access to parts is very limited.  I have measured the ohm resistance of the buttons, checked the vacuum hoses.  I am not a kind of a guy that writes on the internet before he opens up the hood. I will take the servo apart tomorrow ans see what I can find inside, try to measure the tps for consistency and such.

[Gary Lewis]

Romel - You don't have a TPS on a diesel do you?  And I don't see anything in the schematic for the speed control that requires any input from the engine.  It gets the input from the speed sensor and you tell it when you want it to keep that speed.

So I wouldn't start taking the servo apart.  There are testing suggestions in the Speed Control section of the EVTM and I'd try those.

Do you have the factory service manual?  The EVTM says Section 37 has more diagnostic info, and if you don't have the service manual I will scan that section in this evening.

[Steve83]

Gary Lewis wrote

...don't have a TPS on a diesel...

The TPS is inside the servo - it's what tells the cruise module where the servo is.  It has nothing to do with engine management.

[Romel]

I thought the potentiometer in the servo is basically TPS, I have found some good info on cruise control on the internet. I try to examine more if my back decide to work. I am almost 2 months home with hernia of vertebrae disc, so a lot of time on the internet, but actual work limited to whether I can move or not. I try to examine the servo, I think good write up here http://www.thorssell.net/hbook/ccptest.html  I will try this and see.

[Gary Lewis]

Sorry about your injuries.

I've scanned Section 37 of the 1985 factory shop manual and embedded it on the page at Documentation/Electrical/Speed Control, and on the Instructions tab.

I'm not saying this is far better than what you found, but it is 37 pages long and written by Ford for their tech's.  

[Romel]

Thanks Gary, I have lots of time for reading, thank you for scanning the documents.

[Gary Lewis]

Enjoy.  And, get better.

Unfortunately my printer/scanner is not working in the shop, so I had to use my wife's and it isn't nearly as good as mine.  But, I think those pages will work ok.