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Calling all NAXJA electronic gurus

P

PuddinHead

NAXJA Forum User
Location
Virginia
I just know I'm going to gets lots of responses on this one. Has anyone actually repaired one of those yellow AMC cruise control boxes? I've looked at everything else on the system and can't find anything wrong. I picked up 2 yellow boxes from the junk yard and still no go.:rattle: Two chips cross to LM339, but there's another chip on the cb, probably some kind of counter. I've tested the servo on the firewall, checked the vac lines, checked the vac switch under the dash, tested the speed sensor under the dash, ohmed the wires from the terminal block that plugs into the yellow box to where they're supposed to go (to the stalk switch and to the servo). I'm stumped and I don't like giving up. Thanks in advance for any help.
 
If two more junkyard units didn't work, I'm guessing its not the box. By vac switch under the dash, did you mean the white switch high up on the pedal? I know that breaks the vacumn on the system when the brake is pushed, but I don't recall if that or the regular brake switch is what tells the cruise to let go.

At least I didn't tell you to fiddle with the pots on it to fix a loose steering. :}
 
I have fixed 3 RENIX cruise control systems and with all 3 the problem was a break in one of the small wires that come from the switch to the steering column. I have not seen a failed RENIX CC box yet. If you look at the front of the turn signal rod where this switch assembly attaches, you will see a small black tube that comes out of the switch body and follows the rod into the steering column. I think there are 4 wires inside. These internal wires break at the point where it exits the plastic switch body. If you do some continuity checks at the CC module, through the various switches and back to the CC module, you should find the problem. If you find continuity is good, wiggle the wires at this point while holding the switch actuated.

If you have a Saginaw Steering colum (I think up to '91), the switch is common to many Chevy, Buick, Olds, etc. I bought mine on ebay for about $20 each.
 
that is what that yellow box is that says AMC on it i have asked like 10 ppl and nobody knew i guess you learn something new every day
 
lawsoncl said:
If two more junkyard units didn't work, I'm guessing its not the box. By vac switch under the dash, did you mean the white switch high up on the pedal? I know that breaks the vacumn on the system when the brake is pushed, but I don't recall if that or the regular brake switch is what tells the cruise to let go.

At least I didn't tell you to fiddle with the pots on it to fix a loose steering. :}
Click to expand...

I tested the white vac switch to make sure it would hold vac and then vent when the brake pedal is pushed. I'll have to double check it electrically. I've been wrestling with this thing so long I don't remember if I tested that part or not, but I think I did.
 
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MoFo said:
I have fixed 3 RENIX cruise control systems and with all 3 the problem was a break in one of the small wires that come from the switch to the steering column. I have not seen a failed RENIX CC box yet. If you look at the front of the turn signal rod where this switch assembly attaches, you will see a small black tube that comes out of the switch body and follows the rod into the steering column. I think there are 4 wires inside. These internal wires break at the point where it exits the plastic switch body. If you do some continuity checks at the CC module, through the various switches and back to the CC module, you should find the problem. If you find continuity is good, wiggle the wires at this point while holding the switch actuated.

If you have a Saginaw Steering colum (I think up to '91), the switch is common to many Chevy, Buick, Olds, etc. I bought mine on ebay for about $20 each.
Click to expand...

I tested the stalk switch by measuring voltage at the terminal strip for the yellow cruise box. There is a supply wire +12 volts and three "outputs" from the stalk to the cruise box. ON, SET and RESUME. I got 12 volts at the box each time I pushed one of these switches.
 
jneary said:
older jeeps break the wires at the brake light switch. or some of the newer ones can still go bad even if the brake lights work
Click to expand...

Some PO did some wiring on those switches because there are aftermarket connectors there. Anybody got a wiring diagram of these brake/cruise switches? That may be my problem.
 
cruise.jpg
 
Mine never has worked either. I don't recall seeing that 4 amp inline fuse either. I wonder where it is physically located? Looks like it might be on the column somewhere.
 
Ecomike said:
Mine never has worked either. I don't recall seeing that 4 amp inline fuse either. I wonder where it is physically located? Looks like it might be on the column somewhere.
Click to expand...

The cruise box fuse hangs free under the dash in an 'inline' socket. Mine is ok, else I wouldn't get power to the stalk switch which I measured at pins 5, 10 and 14. If I'm looking at it right looks like when you push the brake +12 volts is supplied to the cruise box? Maybe that resets the thing? Look at Ignition Connection Pin 7 wonder if that is plus or minus?
Drawing shows a clutch switch with one side indicated for A/T and other for Manual. The auto side shows NCA. Is this Normally Closed 'A'? Where is 'A'? Maybe the vacuum valve switch? To me the drawing shows a normally closed switch in series with a normally open switch connected to the blue wire with tracer that goes to cruise box pin 13???
 
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Pin 7 traces back to the "gauges" fuse, so its a +12 feed when the ignition is on. Might be easier just to probe pin 13 and hit the brake pedal to confirm it changes. The pink wire from the hazards I believe is also a +12v feed.
 
lawsoncl said:
Pin 7 traces back to the "gauges" fuse, so its a +12 feed when the ignition is on. Might be easier just to probe pin 13 and hit the brake pedal to confirm it changes. The pink wire from the hazards I believe is also a +12v feed.
Click to expand...

Pin 13 supplies +12 volts when the brakes are applied. NCA looks to be a bridge. The vacuum vent/switch isn't shown in the drawing. It is normally closed and supplies ground until the brakes are applied.

I went back through and tested everything under the dash, tested the servo on the fire wall and tested the stalk switch. Everything works normally. I also re-tested the speed sensor on the odo cable. It measured about 105 Hertz a@ 45 MPH and on the AC scale it produced 1.5 volts @ 45 MPH.

The only thing I can't test is the yellow cruise box. I replaced two of the quad comparator ICs with equivalent LM339s (Radio Shack). Nada. No worky. If I was somebody else this would piss me off.
 
I see that the brake switch has two set of connections. I think one set provides power to the rear brake lights and the other set kills the cruise. One set drives a relay which i need to pull and test because sometimes my brake lights work and sometimes not. This means another trip under the dash standing on my head. This will probably not net me anything, but its my final attempt at repair. Anyone have any other repair suggestions other than just forgetting it?!!!1
 
At least good to hear i'm not alone... I have same prob. This is what i did a few months ago:

- Switch on column-check!
- Switch on brake pedal-check!
- vacuum release-check!
- no vacuum leaks-check!
- Servo functioning-check!
- Speed signal-check!
- In-line fuse-check!
- Tried swapping the control module-check!
- All ground points ok-check!
- Good voltage at control module-check!
- Big stupid connector on firewall- cleaned...


All tests have been done according to FSM where available data could be found.... Gave it a rest to allow my back to heal after all the upside down under/inside the dash action, but will get back to it soon...

Come to think of it: I think i will do a full test on the ecu unit. Check all input signals at the ecu connector. If input is OK: Check output signals on the ecu connector. If output signals on ecu are ok (and servo is working) it should be the wiring between ecu and servo.... do the ohm!
 
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xj88kjetil said:
At least good to hear i'm not alone... I have same prob. This is what i did a few months ago:

- Switch on column-check!
- Switch on brake pedal-check!
- vacuum release-check!
- no vacuum leaks-check!
- Servo functioning-check!
- Speed signal-check!
- In-line fuse-check!
- Tried swapping the control module-check!
- All ground points ok-check!
- Good voltage at control module-check!
- Big stupid connector on firewall- cleaned...


All tests have been done according to FSM where available data could be found.... Gave it a rest to allow my back to heal after all the upside down under/inside the dash action, but will get back to it soon...

Come to think of it: I think i will do a full test on the ecu unit. Check all input signals at the ecu connector. If input is OK: Check output signals on the ecu connector. If output signals on ecu are ok (and servo is working) it should be the wiring between ecu and servo.... do the ohm!
Click to expand...

I haven't tried to check the outputs from the cruise control ecu, but I have ohmed the wires and checked for grounds on said wires from the cruise box to the servo. All appeared good. Like I've said before the only thing I haven't tried to test is the cruise control box itself. The little yellow devil. Whatever is wrong, its not halfway dead, it's like the cruise box is not getting power.:dunno:

If you're talking about testing the engine ECU, I don't think the cruise is connected to it. The system is pretty much stand alone, picking up power inside the cabin with the cruise control box wiring and vacuum hose running out through a common grommet in the firewall to the servo which opens and closes the throttle. At least that's the setup in my 90.
 
PuddinHead said:
I haven't tried to check the outputs from the cruise control ecu, but I have ohmed the wires and checked for grounds on said wires from the cruise box to the servo. All appeared good. Like I've said before the only thing I haven't tried to test is the cruise control box itself. The little yellow devil. Whatever is wrong, its not halfway dead, it's like the cruise box is not getting power.:dunno:

If you're talking about testing the engine ECU, I don't think the cruise is connected to it. The system is pretty much stand alone, picking up power inside the cabin with the cruise control box wiring and vacuum hose running out through a common grommet in the firewall to the servo which opens and closes the throttle. At least that's the setup in my 90.
Click to expand...

nope, I'm talking yellow lunchbox :looney:. ECU= Electronic Control Unit or Engine CU? tired of writing cruise control unit over and over... :dunce:
 
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