Backlighting for Climate Control and 4X4 shifter always on

[johnsonmtz]

The back lighting for the 4x4 floor shifter and the climate control module are on constantly in my '89 K1500 and will not turn off causing the battery to drain. The lights remain illuminated even when the truck is not running and key is removed from the ignition. The backlighting for the gauge cluster only comes on with the headlamps and I've also confirmed the dome light only turns on when the door is opened or through the dimmer switch. Finally, we've also confirmed the courtesy light in the engine bay is turning off when you close the hood. So, it seems all lighting circuits and switches are working properly except the climate control and 4X4 shifter backlighting.

I found a source to download the wiring schematic for the truck but have to admit I haven't fully studied it yet to track down these circuits. I can turn a wrench pretty well but electronics and wiring aren't my strong suit so I'd appreciate any help I can get. I would appreciate any information for wires/locations to trace and troubleshoot this issue. First off, I'd like to confirm when these lights are supposed to be on: is it always on when the key is in the run position or is it only when the headlamps are on? Second, where do these bulbs get power: is it through the headlamp switch or does it come through the run circuit in the ignition?

Thanks.

 

[johnsonmtz]

So far it seems the schematic is showing a grey wire powered by the 5A Panel Lamp fuse provides power to these lights through the Audio Alarm Module in the Convenience Center. I'm assuming I could just pull that 5A fuse and temporarily fix the issue, but I'd really like to solve the source of the problem and not have to do this.

I would appreciate any information/knowledge on what this Audio Alarm Module does and how it works.

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[pressureangle]

The middle diagram is where you are; it shows that the panel lamp fuse connects directly to the lamps in question without any switches in between, so the issue is between the fuse and the upstream power. I would expect the power to come from the headlamp switch at the same point as the gauge fuse. It's possible that the wires have been hot enough to short the panel lamp fuse line to the battery + line coming in. I'd have a close look at the headlamp switch, switch plug, and harness wiring nearby.

 

[johnsonmtz]

The middle diagram is where you are; it shows that the panel lamp fuse connects directly to the lamps in question without any switches in between, so the issue is between the fuse and the upstream power. I would expect the power to come from the headlamp switch at the same point as the gauge fuse. It's possible that the wires have been hot enough to short the panel lamp fuse line to the battery + line coming in. I'd have a close look at the headlamp switch, switch plug, and harness wiring nearby.

Yep, you're right. Looking closer at these diagrams and doing a little searching I've learned more about the Audio Alarm Module and I now suspect that may be my problem. I discovered this is actually what I would call the door chime and realized that ever since we've had the truck I've never heard it make a sound. Whether I have the key in ignition, headlights on, seat belt....nothing, nada, quiet as a mouse.

Since the grey wire that illuminates these bulbs comes out of that module I'm thinking something may have failed internally causing a short that has created my problem. Tonight I'm going to pull the module and see if the lights go out. If they do, that at least confirms the module is the point that powers all of them. Next I'll test the module and see if there are any shorts between pins. If the module is bad I plan to upgrade to a 14101255 so it gives me the chime sound instead of the constant buzz.

 

[johnsonmtz]

Well, on to square 1. Looked under the dash and the audio alarm module doesn’t exist. Previous must have pulled it so they didn’t hear the chimes or get seat belt warnings. .

 

[pressureangle]

It appears that the gray wire actually *powers* the alarm module rather than that being the source. Look at the second diagram again, the fuse connects directly to the lamps that stay on, apparently including the 4x4 console lamp. If the module plug is accessible, test the gray wire for power and see if it is actually connected to the same fuse.

 

[johnsonmtz]

I haven't fully diagnosed the problem, but I have some new clues. Originally I thought the problem was in the Convenience Center. However, recently I was pulling the fuse for the courtesy lights because I was working on door pins and didn't want to run the battery down. When I grabbed the 20A fuse to pull it i wiggled a little and I heard the Climate control cycle and the 4x4 light come on. I can repeat this by simply pushing and wiggling the fuse at any time.

I now think my issue is actually in the back of the fuse block and the wire for the KEY ON position is shorting to a positive post and leaving the truck continuously with power to the dash.

Any idea which color wire is the KEY ON circuit? I can try to figure it out from the manual I downloaded, but a hint in the right direction would be appreciated.

Thanks.

 

[AK49BWL]

I haven't fully diagnosed the problem, but I have some new clues. Originally I thought the problem was in the Convenience Center. However, recently I was pulling the fuse for the courtesy lights because I was working on door pins and didn't want to run the battery down. When I grabbed the 20A fuse to pull it i wiggled a little and I heard the Climate control cycle and the 4x4 light come on. I can repeat this by simply pushing and wiggling the fuse at any time.

I now think my issue is actually in the back of the fuse block and the wire for the KEY ON position is shorting to a positive post and leaving the truck continuously with power to the dash.

Any idea which color wire is the KEY ON circuit? I can try to figure it out from the manual I downloaded, but a hint in the right direction would be appreciated.

Thanks.

Depends on which circuit you're looking for. From the ignition switch to the fuse panel, Brown is hot in Run/Accessory, for the radio, wipers, and windows. Orange is hot in Run only, for the HVAC controller mostly.. Pink is hot in Run/Start, running the cluster, engine electronics, and ECM. Based on the HVAC system cycling, I'd say you're looking for a loose large-gauge orange going into the fuse box, probably one of the bus bars. The fuse box has multiple rows that are fed by bus bars with only one wire going in... One may have come loose and is shorting stuff together.

 

[GoToGuy]

Did you download the OE service manuals on the forum download links? There are year specific OE service manuals , having, all the wire digrams location, routing , all the factory info. With the OE you could completely disassemble and reassemble the complete truck. They will be your new best friend. Enter " service manuals " in the search bar at top. A few paragraphs down you'll find the member who has the links to get them . The not hard to use, more complete, not vague and generic like aftermarket manuals. Some years have more than one volume download all for your year. You never know, you might wanna rebuild your power steer pump yourself. Good luck.

 

[johnsonmtz]

Sorry it’s been so long but I want to wrap up this thread. I finally got a chance to pull out the fuse panel and see which wire was loose or bare that was causing the problem. Turns out, it was just a loose screw. The problem starting shortly after my son did some speaker work and I thought he had pinched or pulled a wire. Apparently while doing this he had dropped a screw and never found it. The crazy screw landed on the back of the fuse panel and was bridging between the orange 12v wire and the key-on climate control circuit.

Thankfully there were no other problems so I should be in good shape. Some days I just have a screw loose…..literally. Thanks for all the info and guidance.