Cruise control in 98 Stratus

Since the I've had the car ('98 Stratus, 180,000+ miles now) the cruise control has intermittent failures. The ways it happens are:
1. After start driving, turn the CC on, the CC light comes on. Pressing
the set speed button makes the light come off. Can't be turned on again unless I shut and restart the engine. Usually works fine after the restart. 2. Having driven a long time, with CC working fine, come into city traffic, have to brake/accelerate. After passing through the city traffic, want to resume cruise, pressing the resume button shuts the CC off, as above. Again restarting engine makes it work fine.
These effects are more pronounced in warm weather; in the winter it happens very rarely; in the summer - almost daily. Something else - after each "major surgery" on the engine, the effect disappears completely for 3-4 months. After changing the head gasket, the rear main seal and the cat converter (each on a separate occasion) the CC worked fine for the next 3-4 months. Each time I was hoping that it was fixed permanently, but it came back.
Now the warm weather has returned, and it's happening again. I would like to figure out why it's happening, if not fix it, before the car eventually departs (it won't last forever, unfortunately). The several attempts to diagnose it at dealerships have failed - it's working fine when there, and the scanning tool shows nothing (admittedly that's what they tell me - I have no idea what tool they use and which parameters they read).
Can somebody (maxpower?) suggest a sure way to diagnose the reason? Do I need to go to a garage right after it shuts off, with the engine left running? (Usually that's impossible, because it happens on the road far from known dealerships/garages and I can't drive the rest of the way w/o CC). Do I have to tell them what specific scan tool to use or which specific parameters to look at? Or maybe something else to look for?
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Glenn, did you see/read this? Do you have any suggestions how to diagnose?
Patok wrote:

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Patok wrote:

Have you pulled the diagnostic codes? My SWAG would be that you see something pertaining to the output speed sensor. There should be at least SOME clue in the stored codes.

You can't drive without cruise? Sheesh, only one of my cars even HAS cruise control (the wife's) and I rarely use it :-p
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restart.
The engine controller would have to be scanned for fault codes to start the diagnostic procedure. The DRB has the capability to see what the last cut off was on the cruise as it was working. In other words.... if you are using the cruise and it just shuts off for no reason at all......you would have to have this scan tool connected to see what deactivated it. It would show, brake switch, vacuum, speed and so on. The most common problem would be the brake switch. Sorry not much help here
Glenn Beasley Chrysler Tech
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restart.
Second reply
The engine controller would have to be scanned for fault codes to start the diagnostic procedure. The DRB has the capability to see what the last cut off was on the cruise as it was working. In other words.... if you are using the cruise and it just shuts off for no reason at all......you would have to have this scan tool connected to see what deactivated it. It would show, brake switch, vacuum, speed and so on. The most common problem would be the brake switch. Sorry not much help here
Glenn Beasley Chrysler Tech
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maxpower wrote:

I must agree with Glenn in that it is likely the brake light switch. It is a mechanical switch and the cruise control brake signal circuit does not draw enough current to keep the contacts clean. My cruise control would disengage for no reason ('98 Stratus ES). Took it to the dealer and they replaced the servo but that did not fix it. I replaced the brake light switch with a Dodge part and it has worked perfectly since (6 years now). If it were vacuum related I would think it would not be able to maintain speed at times. The cruise will disengage if the actual speed drops below the set speed by 10 MPH or so.
--
Gyz

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