Welcome to JA my name is Mark.
By far the most common problem with cruise control operation is a faulty brake light switch. The power supply for the circuit travels through the brake light switch, so a faulty switch will interrupt the power supply to the system. The cruise control circuit is a separate circuit from the brake lights so although the brake lights may work fine the cruise control portion can still be faulty.
Putting in a new switch is the easiest and cheapest place to start.
Dodge Technician
22 Year Chrysler/Dodge Certified Specialist
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Alright I see you made 2 responses and I just read the last one.
Ok, so we have a new switch and no change. Do you have a volt meter to do some tests?
Alright, if you can hear the servo click then the power is present from the PCM, to and through, the brake light switch and to the servo. So we know that portion is functioning. Does your cruise light on the dash work now?
Since the power feed appears ok, we should look at the vacuum circuit for the servo. If you dont have a vaccum pump you can also use you finger to plug vaccum lines and check for a suction from the line when you remove your finger.
Also you will need to follow all the vacuum lines to be sure there isn't one cracked and leaking.
Alright, let's have a look in the steering column. Remove the column covers and lets have a look at the wiring going to the clockspring. Quite often they can break if you have a tilt column.
Hi Mark, pulled covers and the wires and connectors look fine. I checked with my OBDII tester and can find no fault codes. My manual shows me the same electrical diagram you sent me. Can you suggest someplace to check voltages or the best next step.
Thanks
Lonnie
Hi Lonnie, here is some testing you can do at the servo.
The engine must be started and running for the following voltage tests.
Here are the specs for the switch as well.
You can also monitor the voltage on the brown yellow wire at the clockspring. With the connector disconnected you should see about 5 volts. Once you plug it in you can use a paper clip to back probe the connector and check the volts as each switch button is pressed. Each switch button has its own resistor and this will alter the voltage on the brown yellow wire.
Hi Mark, I checked everything you suggested, all items checked OK except for item #4, there was no voltage at pin 3 on the harness. I disconnected the brake switch and compressed the plunger to simulate Brake off condition. 1st contacts n/o, 2nd n/c, 3rd n/c. I started the engine and checked power to connector, 1st pair power to white/red wire all the time (brake lights), 2nd pair power to yellow/red wire when cruise on button pushed, 3rd pair pink/black wire powered all the time. When I jumpered at the connector 1st set brake lights come on, 2nd pair jumpered sent power to pin 3 on the servo connector, 3rd pair jumpered drops power to yellow /red wire in the second pairing (cruise) My question is what is the 3rd set of contacts for and should the pink/black wire have power all the time?.
Alright, so we are back the brake light switch. Below is a pic of the switch and all 6 wires and the 3 sets of contacts.
You will see the set of contacts on the left side of the switch are closed in the "relaxed" or off position. This means that if you have to jumper the "second pair"........then there is no power going through the switch as it should, according the diagram showing that the contact between the yellow/red and dark blue/red is closed in the relaxed position.
So it would appear you have a bad switch or or it wasn't adjusted correctly when you installed it. Here is the installation procedure...
And to answer your last question about the pink/black wire...yes this is fused battery power to the switch so it will have power all the time.
Alright, I think there might be something amiss here.
The diagram is for illustration purposes and doesn't represent the wire connector at the switch. I'm curious what you are basing your statements on when you refer to the wires being "flip flopped. I'm also not certain what your n/c and n/o are referring to. I am thinking n/c is no continuity?? But n/o???
I'm including a pic of the wire connector at the switch and the function of each wire. I am adding in the '99 one in case you may have a 99.....it is different from the 98. Let me know if this is of any help.
1998
Hi Mark, I unplugged the connector at the brake switch and verified the color code to what you show for the98 Durango. With the engine off I checked for grounds, then I checked voltages with with engine running.
Cav engine off engine on resist reading (to Ground)
1 0 Volts 13.5 V 621 ohms
2 0 V 0 V 2 ohms
3 0 V 13.7 V infinate
4 .03 V .3 V 46 ohms
5 0 V 0 V 3 ohms
6 13.8 V 13.8 V 12 Volts
Cavity number 3 on the list says ground but I get no ground and get power with engine running and cruise button depressed.
Alright, but the second chart I sent for the 99 shows cavity 3 as speed control on/off switch, which is what you have apparently, so that part seems ok.
With the switch plugged in you still need to get the power to come out of the switch. It is getting there on cavity three, so it needs to come out on cavity 4.......according to the 99 chart.
If you are still unsure of which wire should have the power you can go the the servo and match up the wire color....should be the same.
I'm guessing they have messed up these 98 diagrams a bit as there is no need for 2 grounds at the brake light switch.....so that is why I went to the 99 diagram to see what it said.
Hi Mark, I rechecked everything you first suggested.
1. No power to Pin 3 of 4 way harness to servo (DB/RD wire) when cruise on.
2. Unplugged brake stop lamp switch and checked continuity to Cav 4 (DB/RD wire) to pin 3 of 4 way servo harness (DB/RD wire) OK, also checked to make sure not grounded.
3. Unplugged servo, put 12 volt external power to pin 3, pins 1,2,4 had 12 volts.
4. With stop lamp switch connector unplugged started engine, push cruise button on and got 13 volts to Cavity #3 (YL/RD wire)on connector, plugged back in to stop lamp switch and backprobed #3 to find power had dropped out.
Alright, so you are getting the cruise control on/off signal to the brake brake light switch.
This is the power going into the switch.
You have verified the wire connection from the switch to the servo.
So what is left?
The switch!
Maybe your parts store sold you the wrong switch or it is just plain faulty. But I would suggest you get a dealer switch.
Well, that doesn't surprise me, I alluded to that fact earlier. These are Dodge's diagrams, not mine, and I am only following the info supplied by Dodge.
To answer your question, no.
Very seldom there are any tests that will confirm or deny whether the computer is doing it's job. It boils down to a process of elimination.
If you cannot find fault anywhere else then the computer is "deemed" to be faulty.
You're welcome.......but it is frustrating when the manufactuer supplies the wrong info!
Sometimes this happens in our shop and we end up chasing our tails.