ET RAM

I sure have been all messed up following this Haynes manual. I saw the PCM schematic and saw how the brake switch was wired. It shows the CC going to the seat side pins on the switch.

I did a lot of checking thinking this was correct. WRONG.

Today, I was answering a question on another forum and had to look at the manual again, in the brake section. There I saw the brake switch with the pin numbers and it is different from the schematic. This one shows the CC to be the center pins. Now this makes sense since one of the wire colors for the pins matches the servo feed wire. This wire color had me confused.

So all the testing I have done was with the wrong thing in mind. Oh well.

This is what I have found out. First, I rechecked the vacuum again. It is holding vacuum so that in not a problem. It is showing no codes. With the switch harness removed from the switch I did not get any voltage to the CC contacts, the middle ones, until I had the truck running and the CC turned on. I got alternator voltage 13.86 on pin 3 the CC feed wire yellow/red.

I tested the switch for continuity on all pins and it is working good. I also checked the pins as I moved the plunger and it worked. So, the switch is good. Same as the new one that I had tested.

I connected the harness and reinstalled the switch. I went thru the voltage checks I had done with the harness disconnected. Now, with the engine running and CC on I was getting 13.86 on pins 3 and 4. So power is good at the switch.

I disconnected the servo connector with the harness removed at the switch, I had continuity on pins 1, 2, and 4 and no continuity on pin 3 which is the power wire blue/red. This wire color now matches the wire color at pin 4 at the switch. Now it makes sense.

With the harness connected at the switch, I had continuity on all 4 pins at the servo.

Here is the problem. I reconnected the harness at the switch, started the engine and turned on the CC. I got 13.85 at pin 3 at the servo. But, each time I checked the voltage, the CC would turn off. Then I had to turn the engine off, restart and reset the CC. I would have voltage at pin 3. Once I checked for voltage the CC would turn off.

I did this quick one time and I went to the CC switches on the steering wheel and saw it on and then turn off.

Not sure why this is happening. It still will not engage. While the servo is connected, the CC turns on but does not set the speed and it does not turn off by itself.

When I get a chance, I am going to try the servo power checks to see how it does.

I hope all this makes sense. The pin info in my previous posts is wrong.

Now, I have a question. My truck has a manual transmission. I could disconnect the CC by just stepping on the clutch pedal. I have looked at the pedal and I cannot find how the CC is turned off at the clutch. Does anyone have any info on this? I will be reading the manual again and see if I can find some info.

Thanks.

infidel

You really need to buy the Diagnostic Manual if you're ever going to figure it out.
$21 here www.techauthority.com

mechrisme

I have a service manual that I've downloaded and it shows more then alldata does and I got all the diagrams needed so I just gotta spend some time testing everything, I found a short in the power to my ecm just testing too

dguru

They usually do have a switch on the clutch that will dump the cruise just like the brake light switch. The factory manual does not show it but every manual trans truck that I have seen with cruise has this feature to stop the engine from over reving when the clutch is depressed.

The switch could be before or after the brake light switch but does the same thing.

ET RAM

Bill,

Thanks for that link. I called Techauthority today and was told they do not have the Diagnostic Manual for my truck. They said that they had the Factory Manual in hardcopy for $90.00. They said all the CC info was in that manual.

Is this the best place to buy a factory manual or are there other places to consider? I probably should just go ahead and get a FSM.




dguru, Thanks for the info. I have looked all over to see how the clutch disengages the CC but have not been sucessful. I was thinking that if there was a problem there, the CC would not engage.

Maybe one day I will solve this problem. It is just not worth taking to a dealership.

dguru

Is everything else on the truck working?

An easy to understand bypass can be done. Make a jumper that connects to pin 3 DB/YE wire on the cruise control servo under the battery. You will have to strip some insulation from the DB/YE wire to do this. Crank the truck and hook that jumper to the Pos battery terminal and road test it. If it works the problem is in the brake light switch, wiring or the feed that supplies it. Be aware that if the cruise works you will have to turn it off with the cruise switch in the steering wheel because the jumper will bypass the brake switch. Be careful not to lose control and have a wreck. Turn off the engine if all else fails. I don't like to test things this way but you are having so much trouble this will help you locate the problem.

Another note is the cruise will not work till you go at least 35MPH

Busboy

First, the brake light sw's are a known problem. As you know there are 3 sets of contacts (so any set could work or not on their own), one open 2 closed. The open contacts are for the brake lights, the other 2 are for the cruise. One set allows the cruise to be turned on while the other disengages it. Modern cruise control use a sudden increase in engine RPM to disengage the cruise, this could be clutch depressed or put into neutral. It also disengages with sudden decrease in speed, sudden stop like an accident or sudden increase in speed like wheels spinning. To engage the cruise you need 35mph(i think), brake pedal not pressed, not in neutral and there may be another thing I don't remember. The PCM takes care of this so battery connections and grounds are important as low voltage is used.
To start I would change the brake sw ($15?) then clean all the battery connections and grounds. Is your park brake light out and is your tach stable?

ET RAM

Busboy, thanks for the info. I have checked that switch several times and it tests good. I even tested a new one at the auto shop and both tested the same. Everything works correctly except the CC.

dguru, I am going to try what you suggest. I was thinking along those lines. The feed wire to the switch is good. I have voltage there. I believe the problem is in the wire from the switch to the servo. I can get voltage at pin 3 of the servo but lose it when I do a voltage check.

I am going to test it again. When I lose voltage at pin 3 servo, I will check for voltage at the feed wire going to the switch. If I have voltage there, the problem is in the wire from the switch to the servo. I will, also, do a continuity test with the harness disconnected at the switch.

Any way I will check this out. I am used to doing jury rigged tests. Being in the country I don't have too much risk of hitting anything. Although, I have seen cows on the road a few times.

Thanks all for the help.

infidel

There is no direct wire from the switch to the servo.
It goes to the PCM which determines whether to throttle up or down based on input from the vehicle speed sensor.

Cruise problems I've run into besides the typical have been a bent male pin at the brake light switch that didn't make connection and enlarged female connectors at the PCM from a meter probe.
Only way to see the bent pin was with a mirror.
Both problems were from the owners trying to fix something they knew little about.

dguru

infidel
Not trying to be mean or anything but DB/RD wire that runs from the brake light switch goes direct to the dump solenoid in the servo. It is basically the power feed to the servo. The PCM controls the vent solenoid and the vacuum solenoid(these ground to operate and get feed from the dump wire). The brake light switch interupts the feed when the brake is pressed. This causes the servo to dump vacuum.

If you don't get power to the dump solenoid nothing works.

I do agree that the brake light switch is the most common problem. I bet the problem here is a corroded wire under the battery but I am not sure if he has properly tested the brake light switch at this point.

ET RAM

Looking at the schematic, that is how I see the system. That is why I want to do a continuity check on the wire from the servo plug to the switch connector. I did have a lot of battery corrosion in that area. I had to clean it up and then painted the area with an aircraft battery acid paint.

The brake switch tests good everytime I check it. I use a 9 volt horn continuity/voltage tester that I made. The horn sounds with the pedal up and goes off with the pedal pressed. I even checked for cross continuity between all pins. I also checked continuity during the plunger movement. It just checks out good. A new switch at O'Reillys tested the same way. I am tempted to buy a new switch but think I will be wasting my money.

I am going to test continuity again and this time use a meter and see what readings I get.

infidel

dguru, you are correct.
Difference is I may have wrong assumed ET was referring to the cruise switch, not the brake switch.

ET, a fellow who threw every part there is to a cruise control on a '95 gave me all the good parts after he sold his truck.
If you find what's wrong I probably have the part.
In fact I have three or four of some of them...

ET RAM

infidel,

thanks for the offer on parts. If I can figure this out I may take you up on the offer.

I see now what your thought process was. The CC switch works and turns the system on and off. I get voltage to the brake switch. It just drops off after the brake switch. I see it at the servo plug pin 3 and then it drops off when I do a voltage test. Maybe it is the wire.

dguru, I am going to run the jumper thru the cabin with an on-off switch. This way I can control the power feed and be able to shut it off if needed. I can also attach a voltmeter and see what the voltage is doing.

Thanks for the help.