Cruise control will not work .

-
stroker402

stroker402

1968 dart GTS convertible
Joined
Jan 30, 2006
Messages
1,088
Reaction score
466
Location
milwaukee wi.
1968 dart cruise control will not work. what should I look for or check to find out why it will not working.
I was told that if my speedometer needle is jumping around (which it is ) the sensors in the unit pick up on that and will not engage cruise . Does that sound like the problem ? How do I fix that jumping speedo needle ? lubricate the casing on the cable or lube the speedo gear itself in dash with graphite?
Thanks for you help.
 
Since a 68 never came with cruise, what are you using for the cruise unit - electronic aftermarket or OEM vacuum/cable adapted to your engine? Pics would help too!
 
65 Dartman said:
Since a 68 never came with cruise, what are you using for the cruise unit - electronic aftermarket or OEM vacuum/cable adapted to your engine? Pics would help too!
Click to expand...
ok.
it's a oem vac/cable operated unit to a 1968 340 gts 4v auto . I believe dealer installed. I get pics up later .
It makes sense that if the speedo needle in dash is jumping around the cruise unit can't focus in on a set steady mile per speed.

1968-dodge-dart-gts-convertible-3.jpg
 
Last edited:
I will take a look in my later FSMs for troubleshooting the cruise.
 
On the troubleshooting page of my 71 FSM they list the probable cause and fix for jumping speedometer needle with the vacuum/cable cruise unit. Hope this helps solving your problem

6914D8E5-065A-4525-AC97-0462C7CC85E4.jpeg
 
Last edited:
My brake light switch on my chev truck fixed my CC, wouldn't let it engage
 
How does it know your speed? I would not think there was a sensor in the speedo head that early monitoring the needle? (But my Dad borrowed a Riviera with an overspeed alarm on the speedometer that you could dial in) First thing I would check is cruise control vacuum servo with a mighty vac after you lube the speedo cable with graphite. you can get it powdered in a tube for locks. I dont think grease is the prefered call out for a speedo cable. Let us know what you find.

PS>> there is no sensor in the speedometer head, the sensor is in the CC servo itself as there is a speedo cable going in, and a speedo cable going out to speedometer. I suppose it could be completely mechanical but it would take a mechanical switch/cable to manipulate vacuum signal.
 
Last edited:
lot of areas to trouble shoot here . I see a plug end with electrical wires too.
 
What Pista said - graphite is the preferred lubricant for the cables. I would go sparingly where the cables enter the servo unit as well as at the speedometer head. You could swap a regular speedometer cable from the transmission to the speedometer which will eliminate any issues with the servo/vacuum/electrical part and determine if your speedometer is still jumping around.
 
pishta said:
How does it know your speed? I would not think there was a sensor in the speedo head that early monitoring the needle? (But my Dad borrowed a Riviera with an overspeed alarm on the speedometer that you could dial in) First thing I would check is cruise control vacuum servo with a mighty vac after you lube the speedo cable with graphite. you can get it powdered in a tube for locks. I dont think grease is the prefered call out for a speedo cable. Let us know what you find.
Click to expand...
Yes , I think you are are correct there is no electrical sensor it's all mechanical right ? but there is a plug end with wires .
 
Last edited:
65 Dartman said:
What Pista said - graphite is the preferred lubricant for the cables. I would go sparingly where the cables enter the servo unit as well as at the speedometer head. You could swap a regular speedometer cable from the transmission to the speedometer which will eliminate any issues with the servo/vacuum/electrical part and determine if your speedometer is still jumping around.
Click to expand...
ok .
 
"there is no electrical sensor it all mechanical right ?"

No I believe there is an electrical component to it as the CC is stalk mounted. Probably just a electric servo that opens a vacuum port. Are there any harness plugs on top of your unit? If they are not on the unit, they have to be on the vacuum hose somewhere or maybe its cable operated? Here are two pics of different years, note the lower has no electical harness visible
index.php?PHPSESSID=hqf80kse714mkfdmfbablba750&action=dlattach;topic=114264.jpg
index.php?PHPSESSID=hqf80kse714mkfdmfbablba750&action=dlattach;topic=114264.jpg
 
pishta said:
"there is no electrical sensor it all mechanical right ?"

No I believe there is an electrical component to it as the CC is stalk mounted. Probably just a electric servo that opens a vacuum port. Are there any harness plugs on top of your unit? If they are not on the unit, they have to be on the vacuum hose somewhere or maybe its cable operated? Here are two pics of different years, note the lower has no electical harness visible
View attachment 1715196056View attachment 1715196057
Click to expand...
without taking another look , I believe there were two wires that joined into one plug .
 
Just an FYI- cruise speedo cable sets are cheap on rockauto

I thought they'd be hard to find, but they weren't
 
YY1 said:
Just an FYI- cruise speedo cable sets are cheap on rockauto

I thought they'd be hard to find, but they weren't
Click to expand...


And any decent speedometer place can make any length you need
 
65 Dartman said:
And any decent speedometer place can make any length you need
Click to expand...
I put graphite on the end of cable ends by servo , I'll dry that before I do the cable back of speedo . did notice that there is a wire that goes to the brake lite switch so that looks right.
I have NO Power at the plug end wires at servo with ign on . NOT good there. fuse looks good under dash marked AC.
 
Per the wiring schematic there should be 2 wires going to the brake light switch, 4 going to the turn signal with the cruise controls and 3 wires to the servo of which 2 are on one connector and 1 wire on another. Here are the schematics for the 71 Challenger,

B8D10252-62FB-4315-BE8C-372043B04E71.jpeg

71 Charger/Coronet,

51223E14-31A7-4327-B794-13A8034EF730.jpeg

and 71 C Body
B2F13ED7-B145-407A-A9FE-DA578993740B.jpeg


And here is the harness which is from a later M or maybe J Body but the connectors are the same
54868A7E-6DAD-446F-88B9-D882928A7184.jpeg


The very top connector goes to the turn signal cruise controls, the very bottom 2 go to the servo, in the middle right above the servo wires are the 2 blue ones that go to the brake light switch and the single wire right under the very top connector is connected to a hot wire when the ignition is on (not accessory or hot all the time). Hope this helps!
 
Whether you have the turn signal lever as depicted or the later one, the connectors are the same
 
The spare cruise harness I have is identical to the one in the first picture less the brake light switch.
D5677E01-779B-4DD2-BA52-28609183EF32.jpeg
 
In my post with the pics of the wiring diagram and of the harness, I've pointed out where each of the terminals go - to the cruise function on the turn signal switch, to the brake switch, to the servo and to power. Should point you in the right direction! Good Luck!
 
You must log in or register to reply here.
-

Back
Top