Speedy72t

I'm knee deep in crap & $$$ trying to diagnose the cruise control. I may have found a mistake in the "cruise diagnoses" link that floats around here and I want to run it by you guys.
It states that there should be voltage on pin 11 with the cruise in the ON posistion and the ignition on and that the voltage should drop to zero when the brake/clutch pedal is pressed. I'm beginning to believe the voltage should ALWAYS be at zero. There are three switches involved:brake light, brake vent & clutch vent. The brake light has continuity when open (pedal pressed) and the brake/clutch have continuity when closed (pedals not pressed). Voltage comes from the fuse to brake light switch to cruise stalk switch to brake/clutch vent to cruise computer. So if everything is adjusted correctly you will never have voltage on pin 11. Press the brake pedal hard enough for the brake lights to go on and the brake/clutch vent switches open before the brake light switch closes to light up the brake light.
I had 0.10 V DC on pin 11 but it went to 0.0 V when either the clutch or brake pedal were pressed so based on the diagnostic I ordered and installed a column switch even though the continuity readings on the switch itself seemed good. The cruise worked for one day. So I went back to the drawing board. Now I notice a 12V jump for just a split second everytime I press the brake pedal. So this is my early working theory. If the computer sees full voltage on pin 11 it assumes there is a PROBLEM and shuts itself down. This could explain why it has worked on and off for two years. I'm not even close to being done this but I wanted some feedback from other people with electronics experience.

autibahn

engage the clutch and put it into nuetral what is suppose to happen? Assuming you haven't touched the brake or disengaged the cruise control manually.

GDA4

when either clutch or brake is engaged, cruise control disengages..

Speedy72t

it does make me wonder what the deal is though. why not have all the switches have continuity when open. That way if you hit any pedal the computer will see 12V and shut off. this way I'm not really sure what the trigger to shut the cruise off is. The venting of vacuum is the only thing that I can see which means my problem may be a pinhole vacuum leak.

David.Norton

I think they put a trickle current into the lamps to check to see if the lamps are good, when I measured it I think it came up a few tenths of a volt when the brake or clutch was pressed, and was ground when operating, so if memory serves you are correct and would likely not see the change. I had a similar problem where my switch was bad, replaced it and then the cruise was intermittant (tried to clean it first, then gave up and got another switch when it still didn't work all the time). Soldered some joints inside the can that didn't look good on the connector next, now I'm good.

Speedy72t

I spent another couple of hours on it after this post. It's either the control box itself, something to do with the vac system or something I haven't even thought of yet. With the old parts I was getting as much as .5 ohm resistance on some points but with all the new parts and adjusting the switches I'm getting full voltage and 0.0003 ohm resistance every where else. I even verified as best I could that the speed sensor is operational. When the cruise first died you could here a relay having an epileptic fit. In retrospect I would say that killed the control box. I doesn't explain why it worked good for a couple of days this week but who knows. I did pull the board. The joints looked decent and nothing was burned but it's hard to say. I'm going to see if I can come up with another box tommorow but that's my last chance before we take it on vacation.

autibahn

the revs fly up to like 6500 rmps until i pushed the brake and it went back down. But it scared the crap out of me.

Speedy72t

For the short moment that mine worked today I engaged it while in neutral and it started reving like mad till I stabbed at the clutch to shut it off. Duh.