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Discussion Starter · #1 ·
i have a 78 power wagon (4x4 goes without saying) with a 360 4-barrel. recently the cruise control has been buggin out. ill set it and it will kick in for a little bit, but then ill lose speed. when i push down a little bit on the gas, it kicks in again and goes back to the set speed. it will do this several times before i just get frustrated and turn it off. it used to work perfectly fine until about a month ago. any ideas?

p.s. if my switch is toast, is there any place that sells new ones?
 

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sounds more like the control unit not sensing the drop in speed / the control unit is the thing that the speedo cables go,s into / take it apart and clean it up and regrease it / they get gummed up or wear out
 

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I had the same problem with my 77 but now it holds fine at 35mph or so and doesn't work at all at highway speeds. The damn thing. When it did work, it was one of the best cruise controls I had ever used, rock steady, as good as anything newer.
 

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Discussion Starter · #6 ·
when it loses speed, its just as if i take my foot off the gas pedal. the hose and connections are all good, because it was working up until a few weeks ago. when it quit working, i noticed the lever was really grimy and hard to move. would dirty connections on the switch be a cause, and if so, how do i clean the switch/lever ?
 

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Well it could be the contacts in the switch. The cruise gets it's power through the switch. I've never tried to take one apart..you might just want to get one from the salvage yard and try replacing it.
 

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Turn on your key to the run position, turn your cruise on, and remove the 2 prong plug at the cruise servo. You should hear a light clicking from inside the servo when you disconnect and reconnect the plug. If you have good ears, you can listen for the clicking when you flip your cruise switch to the on position, also it should click when you press set. Mine does not click when I press resume, but I don't think it is supposed to. This might give you an idea if your switch is working.
william
 

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From the WD-40 website...

Cruise Control Troubleshooting

Here's a way to troubleshoot a non-working cruise control. Try wrapping a towel around the cruise control buttons on the steering wheel and douse the buttons with lubricant or cleaner. Then work the cruise buttons back and forth for about five minutes. This simple tip will often make a cruise control work like it's brand new!
 

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I have had good luck with tuner lubricant on electrical parts. It is blue and comes in a spray can and is specifically for lubricating tuner/switches. I discovered it at an electrical wholesaler. The switch does come apart, but it appears to be held with small roll pins, and I would try dousing it like chump said before disassembling it.
william
 

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Discussion Starter · #14 ·
yeah, the roll pins are what held me back from taking it apart. i think my contact points on the inside are not hitting or something. i would rather just replace the whole thing if i could. does anyone have any NOS ones lyin around.....(hahaha), or would i probably be able to find one at the spring fling in april (biggest west coast mopar event)?
 

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I agree with Chump, I would check the servo unit first. The FSM diagnosis is fairly helpful, but I decided I needed to tear mine apart. After getting it completely disassembled (lots of little loose bits, so pay attention!) I found what I think is the problem while reassembling it. I found a tiny tear in the edge of the rubber diaphragm that pulls the throttle cable (with vacuum). I carefully patched it with some rubber patch solvent, and will test it out tomorrow. I also compared the original servo to a newer (early 80's) unit to see if they were the same. They were different, but the electrical, vacuum, speedo and cable hookups appear to be compatable.
william
 

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I replaced the servo on my 75 with one from an 83 Imperial. The bracket is a bit different, but everything else is pretty much a plug in deal. Works A-1 now. I am determined to find out what is wrong with the original though, as it looks much nicer (smaller, all metal) and I would prefer to have the correct unit on the truck. At least it is working now...
william
 
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