Cruise control not working?

Yes, I have power on both sides even popped in a new fuse while after checking. Then checked again.

My cruise control recently stopped working after I washed the engine and I dont know if a plug got wet or the switch went out and if I got a plug wet were would it be located. Also when I push the button the light in the gauge cluster flashes but it wont stay on.

My cruise control (CC) worked sporadically after I installed my LED tail lights. I replaced the turn signal/CC assembly, replaced the stop light brake switch, and Light control module signal flasher (LM487). None of those worked. I finally read on this site to check the 3rd stop light bulbs (cargo stop light). That was the right answer. Both bulbs were burned out and then replaced. The CC began working as the result. Thanks.

Installed led brakkelights high mount and taillights and now cruise dosent work at all no indicator or function at all some told me just coinsidence all fuses I could identify for cruise appear good and all brakelights turn and backups work fine

Cruise control stopped working. I was highway driving and turned the switch to on. I pushed the button to set the speed. I noticed the indicator light on the dashboard lit momentarily and then went out. The cruise doesn't work. I replaced the fuse in the fuse block left driver side of the dashboard. That didn't fix it. An inspection of the old fuse showed it not to be blown. Where do I go from here to troubleshoot the problem?

I had this problem and used the guide to find out my brake light switch was bad, I got a new one $34.00 all good now

When I turn on the cruise control and attempt to set it, the cruise light indicator comes on and then turns off when released. I recently connected a trailer brake controller and connected it to the white wire on the brake pedal switch. Trailer brakes work fine.

Truck listed above is the base model 1500. He's not fancy but he's paid off and normally runs like a champ. Everything worked normally except I had no heat and smelled coolant. I had the heater core replaced. Yeah! I have heat. Bad news I learn a few weeks later my cruise control doesn't work. I do a lot of in town driving so cruise isn't necessary. Well I hit the interstate, flipped the switch, pushed the button and nothing. No light, no cruise. Is there something I can check?

A little background. This truck is a one owner and has been maintained very well by me. No rust, very good condition overall and garage kept until about five years ago.

The problem, sorry but this will be a bit lengthy but the following information is relevant.

Back a couple months ago, I went to the garage to get the truck and run some errands. I was puzzled when I opened the door to the garage and heard the radio playing. I thought "oh great the battery will be dead).

I started the truck and backed out of the garage and turned the key to the off position. The truck was still running and the headlights were still on. To make a long story short, I chased wires and voltage for a couple hours. I also pulled the power center and looked for corrosion underneath which is pretty common. I saw no problems and re installed it.

I "pecked" around with a screwdriver handle in the power center and could make it malfunction so I pulled all the relays and reseated them and the problem went away. Not sure if it would return or not but so far it has not.

About two weeks ago, I noticed my cruise control no longer worked. I hoped it was a fuse but it was not. I kept driving it until I had time to work on it. Last week I happened to be at the rear of the truck while it was idling and I noticed the hi mount brake light was on but dim.

A couple years back, I replaced the stock hi mount unit with an after market LED unit which has been working fine.

I worked on it today and the following is what I have found.

The hi mount brake light is on but dim (sometimes flickers a little but mainly lit about half of normal) anytime the key is on. It doesn't matter if the headlights are on or not.

All three brake lights work as they should
I am assuming the cruise not working is because of this issue. I hope.

I have replaced the brake light switch.
I also replaced the entire power center under the hood with a brand new OEM unit ordered from GM. (It came with all fused and relays installed so everything there is new).

I did this just to eliminate that as a possible issue (and the problem with it not turning off a couple months ago).

I also unplugged the trailer harness under the dash in case it was a problem with the wiring but it was not.

It was suggested that I look at the multi function switch next but I am not sure the hi mount stop light runs through it or not.

My next step is to chase and clean all the engine bay grounds and remove the hi mount light and take a look.

It could be a defective hi mount light assy but there should be no power to the unit unless I push the brake pedal or light up the cargo lights. Somehow there is some voltage feedback getting to the lamp between the brake switch and the hi mount stop light.

It has been a real head scratcher so I am hoping to get some guidance here.

Thanks in advance for any assistance.
Dan

Thank you for your reply

The cargo light does not affect this issue. I mentioned that along with brake light voltage when the brakes are applied, or the cargo light is on would be the only time voltage should be present on that light.

If the ignition switch is on, the led's do light up dimly. I do understand there could be some issues with feedback through the LED assembly, but there should not be any voltage there for the lights to light up when the key is on.

I no longer have the OEM light as it was deformed and was allowing water to leak inside the cab. I chose the LED due to the high cost of another GM OEM replacement.

Even when they are lit dimly, when the brake is on, the lights get full bright as they should.
I will check all the items you suggested and get back to you with the results.

Update:

I removed the hi mount light and tested the voltage to the brake light. The blue wire (which is the one that supplies twelve volts when the brake is pressed) has a constant four volts DC on it when the key is on. I broke the connection to the light assembly to eliminate it and with no load, it still has four volts on it. When the brake is applied, it goes to twelve volts. I need to find out where this stray four volts is coming from.

I am attaching a diagram to illustrate. Since I severed the wire at the light, the only other connection is from/to the cruise control. I have that diagram but they are from different sites and I am not sure where the blue wire comes in yet.

By the way, the cruise worked this afternoon.

More as I find it :)

Update #2:

I started looking for the four volt bleed and started with the VECHMSL fuse and the TRCHMSL fuse. Here is what I found with my testing.

With the key off, there is no voltage across either fuse, normal.
With the key on there is the four volts I also found at the high mount light.

I then activated the brake pedal with a bar and then re checked the fuses mentioned above. They now have twelve volts on them and the brake lights are on full bright.

I unplugged the new brake light switch but it did not change anything.

Looking at the diagram, it appears my next step would be the hi mount relay (CHMSL). It was getting dark and I was not able to locate it yet.

Got to be there or possibly the multi-function switch?

Anyway, I think I am getting close, hopefully.

Thanks

You are correct that the 4 volts is gone when the key is off.

What puzzles me is that these lights just started coming on dim as described. It has been a couple years that they have not with this LED light. Something has changed

I understand that 4 volts is not enough to see using the regular bulbs and I also understand what you are saying regarding the relay.

Everything you describe above make a lot of sense and it is new info for me. Thank you!

I guess my OCD will not let me give up *grin* If it started doing this right away when it was first installed, I wouldn't worry about it but since it is a new problem, it is hard to let it go.

Do you know where the hi mount relay is located? I saw somewhere that it was under the hood on the passenger side but that makes no sense

Thanks again, I really do appreciate all your input