Cruise Control won't work

[boulky12]

I've been trying to get the Cruise Control working on my truck.

First thing I did was replace the Servo (next to the distributor). My old one had holes in it. The one I replaced it with came out of another truck, so it's not new, but it didn't have any holes and it sucked in and out smoothly. After replacing the servo, it still didn't work.

Second thing I tried was the cruise control switch (on the column). I thought this was gonna be it for sure but I just replaced it with a brand new one and it still dosen't work

What else can I try? Is there a fuse for this?

Thanks guys

[hatzie]

What year? 

[boulky12]

What year?

86

[hatzie]

Don't just guess and replace parts.  Hail Mary Shotgun repairs get real expensive real quick.

Download the 1986 GM light truck service manual and the Cruise III Service Training Textbook from my signature link and get out your digital multimeter.  Section 9B pages 1378 to 1391 of the service manual is the Cruise Control test and service procedures.

Check the old and new switches function at the plug with your meter.  I've seen brand new switches that were not working.  Since the new switch didn't fix the problem the old one might be just fine too.

Check the brake and clutch pedal cruise switches with your meter.

There are resistance and voltage checks that should be done on the servo module.  I wouldn't trust a used servo unit till you run the resistance tests with a reliable digital multimeter.  You don't need a $280 Fluke 78 I use a $45 Extech 330 in the barn.  You can print the resistance check page for when you go to the salvage yard and test the little monsters before you plunk down any cash.

This is a complete Kent Moore J34185 Cruise III tester with the manual if You decide you can't live without one.  http://www.ebay.com/itm/like/262260358390?lpid=82&chn=ps&ul_noapp=true

[frotosride]

Any update on this? Mines been out since 2013 when it wouldn't shut off and I had to put the truck in neutral on the interstate and turn the ignition off @85mph..  haven't gotten around to troubleshooting it since.

[boulky12]

Any update on this? Mines been out since 2013 when it wouldn't shut off and I had to put the truck in neutral on the interstate and turn the ignition off @85mph..  haven't gotten around to troubleshooting it since.

Lol. I haven't really messed with it lately. I'm pretty sure its a bad servo but I'm too lazy to take it out and test it and I don't have the funds at the moment for a new one. I'm probably gonna go ahead and spend the 80 bucks for a new one soon tho cause i drive on the highway a lot.

[bd]

Don't just guess and replace parts.  Hail Mary Shotgun repairs get real expensive real quick.

[boulky12]

Theirs really nothing else it could be though

[zieg85]

Leaking/cracked hoses under the dash.  Leaking switch at brake pedal?

[boulky12]

Leaking/cracked hoses under the dash.  Leaking switch at brake pedal?

I'll check it out. Thanks

[boulky12]

So I went ahead and did some tests on the servo.

1st test I did was connect the ohmmeter to pin B and D. Should get 20-30 ohms. I got 0.

2nd test I did was connect jumper wire from pos batt terminal to pin A and E and ground to C. Connect vacuum lines and start Truck. The servo's supposed to pull in. Mine did. Then you pull the jumper from pin E. Servo is supposed to stay pulled in. Mine didn't. Then your supposed to pull off the larger hose and plug it, reconnect E, and start it. The servo is supposed to pull back in sand stay once E is released. If it dosen't the servo is leaking and needs replacement. Mine didn't.

So I think this servo's bad.

[hatzie]

Now you know instead of guessing.  You can do the same tests at a salvage yard.  Considering the quality of the Asian made new parts I'd test new ones too.

My other recommendation is that you run through the troubleshooting tree before you assume the other pieces are in good repair.  A fully working servo may not be the end of it.

[North Central Ohio]

It could also be as simple as the vacuum hose bein disconnected from the resevoir ball or from the "T" fitting,or somethin similar,up against the firewall.