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Discussion Starter #1
So my cruise control has stopped working. Which is annoying, since I prefer to set it at 60mph and chill on the highway, what with only a 3-speed and no overdrive and all.

What's the best way to go about diagnosing these old cruise control systems? I figure it is one of two components (servo or transducer).
 

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Discussion Starter #3
checked the brake lights are working ?
You say this, and it makes me curious. The brake lights do seem to operate normally. But I noticed a few weeks back around dusk while it was running, lights turned off, that the taillights were very faintly illuminated. This was after completely rebuilding the taillight electrical with all new sockets and LED bulbs. Once I shut off power the lights turned off completely. Could this be related?

As for fuses, I'm surprised I haven't checked those. There aren't many to check, as it is. Good old glass tubes.
 

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Discussion Starter #4
Although, I also can't help but wonder if the lighting issue was because of the voltage regulator being bad and overcharging while simultaneously having a worn out light switch. I still need to buy a new switch and cut/grind off the current knob so I can remove the dash panel. The damned knob is glued on. Anyhoo...

Is a switch like mentioned in the Marauder post used on an old 78 Ford? I don't really see replacements listed if they are. Although it couldn't hurt for me to check that switch on my Marauder since the CC hasn't worked in years, assuming it's a wiring issue at the base of the steering column right now. Probably never read that post since I haven't actually removed the brake pedal assembly or the master cylinder/booster on that car.
 

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Forget about my repliea as you never mentioned what vehicle in first post and I was thinking it was the 2003 Mercury Marauder .It helps if you give vehicle as no one remembers every posters vehicles .
 

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Discussion Starter #7
So, if the brake light switch is worn, could I expect to test it for circuit continuity while in the released/open position? I'd rather not just swap parts. I did that with my old Town Car, and the new switch was garbage, requiring the pedal to be nearly fully depressed before closing the circuit. Also turned out the problem was with the connector, not the switch. Maybe I did something wrong, as I was maybe 19 at the time, around 20 years ago, and was still quite green with auto repairs. Either way, just don't want to repeat a mistake.
 

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Discussion Starter #9
We all goof up. No big deal. I usually make it a point to indicate what car I'm talking about, often in the subject, so I screwed up with that.
 

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I dont know the set up on that car but on others there was a brake pressure switch usually on or near master cyl. which if failed , screwed CC.As for the light problem , others on forum are better at electrics than me and might chip in with some advice .
 

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Discussion Starter #11
Not too worried about the lights. That's more of a curiosity than anything right now.

Now, one thing I noticed is that the servo is connected to vacuum. Any idea what kind of trouble can be had with CC with vacuum issues? As it is, I know I still have some vacuum leaks somewhere, so I'm planning to replace the hose connecting the servo to the manifold and that coffee can vacuum reservoir. If it doesn't fix anything, at least I know it won't be an issue down the road.
 

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Have you checked the check valve near the servo? A vacuum leak will definitely mess up cruise control.
 

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Discussion Starter #13
Have you checked the check valve near the servo? A vacuum leak will definitely mess up cruise control.
I did just recently. I realized that I hadn't yet replaced and of the vacuum hoses that run from the manifold on the firewall to the CC servo or the large reservoir can on the fender. So a few days ago I replaced those hoses. I tested the check valve while I was at it, and it seemed ok.
 

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Discussion Starter #14
Ok, so I finally finished the conversion to LED bulbs for everything but the headlights. I had the wrong "electronic" flashers for the turn signals and hazards. With that done, and installing LEDs up front (the rears having been done months ago), I did some checking of stuff.

This all harkens back to my mention of the taillights being slightly lit with the car running. I wanted to check, and they light up just so long as the key is in the "RUN" position. With the new LEDs up front, I wanted to see if it was the regular lights or the brake lights causing the taillights to glow.

I wanted to check this because it seems like in some instances, no matter the age of the car, for certain circuits if you replace an incandescent bulb with an LED, it still lights up ever so slightly, even though the circuit is supposedly turned off. So, I figure once the parking lights and taillights are all on LED, if that's the circuit lighting up, the parking lights should come on as well as the taillights once the key is turned to "RUN". Well, the parking lights did not illuminate, so I'm leaning towards it being the brake lights.

If this is the case, then somewhere along the line the brake light circuit is not being fully opened, thus tricking the cruise control into thinking the brakes are in use. I guess the only way to know for sure is to do one of the following:

> Remove a taillight, pull a bulb and socket, and check to see which circuit is getting powered.
> Replace the LED bulbs in the taillights with incandescent bulbs and see what happens.

I suppose the first would work well with just a multimeter. I'll get to this a later on, though. It's cold outside and I'm hungry. Saturday is looking to be a nice day, so I might take do more investigating on this then.
 

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Discussion Starter #15
Ok, so I found it is indeed the brake/turn signal lights that are getting power. I tested 7.3V with the key in both the run and accessory positions. I disconnected the brake switch and both flashers, and still read voltage.

So, could this be triggering the cruise control, because the circuit has less resistance? If so, what circuit(s) should I check? Or am I best off just wiring in a resistor to each taillight and seeing if that solves the problem?
 
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