CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Seatbelts won't unlock, no dome light, no power to DLC, no radio

1999 Dodge Ram 1500. V8 magnum, 142,000 miles. The first problem I had is this, I was driving down the highway and noticed my seat belt light came on. I was the only person in the truck, and had my seat belt on. Didnt really think too much of it until I got in the truck the next time and couldn’t get the belts to unlock. I could not pull them out of their position to get them to wrap around me at all. Both the passenger seat, and the drivers seat. Also I noticed the next day the dome light wouldn’t work. None of them. No interior lights at all. So on my way to my friends garage to have things tested out, my radio stopped working all together. Got to the garage, noticed that the fuse for the seat belts was burned out. Replaced the fuse, still have the problem. Cannot figure out the dome light problem at all. Checked all the fuses, all is well. As far as the radio, I dont know what happened there. We pulled it out, checked for power, there was no power at all. Messed around with a bunch of different stuff trying to figure out the more major problems, decided to take a break from that and go back to the radio, all of a sudden had power intermittently.



One more thing that I should mention, I had a scan tool on this truck a couple of days ago due to a misfire on cylinders 5 and 8. Had no problems with getting the codes. Cleared the codes, truck is running fine now. However, tonight I thought I should put a scan tool on again to see if I can get any codes. There was no power at all from the DLC. I think this may be more of a headache that I want to deal with but I want to get some opinions on the whole deal if I can before I give up. So does anyone have any ideas on where I should look, or what I should test?

I would start by checking the battery and the charging system.

Fuses don’t just blow----they are caused (by high current) to blow. Something (a short) caused the fuse to blow. The wires to the seat belts and the radio may be connected. You want to check the wiring for abrasion, cuts, shorts to other wires and to ground.
You can spend a few days looking around, or you can engage an automotive electrician ---- especially, if no one knows how to use a multimeter.

I can’t connect any electrical issue that would prevent the seat belts from being pulled out,the issues that I have seen preventing the seat belts from “dispensing” are issues of mounting position or mechanical failure.

I did consider some kind of pre-tensioner issue with the seat belts but I dismissed the idea due to the year of the vehicle (not equipped with a electrical controled pre-tensioner?) maybe a check of seat belt retractor design would clear this up.

So, just a quick question to boggle your mind, oldschool, why would both the passenger side, and driver’s side seatbelt do the SAME thing at the same EXACT time? I highly doubt this is a coincidence that both would fail mechanically at the same time. That’s why I believe strongly that they are actually controlled electronically.

UPDATE: We found the issue. The first thing we did today was start working on figuring out the dome light issue. We figured that they were going to be the easiest thing to get our day going right possibly. We were right. I figured the best thing to do was to get a wiring diagram and figure out which wires were positive and ground, touch the two together briefly to see if the dome lights would illuminate. They did not. Actually, something else illuminated almost immediately, the wires in the dash! In about 5 seconds, maybe less(??) the wires inside the dash board started melting together and caused the inside of the cab to fill up with smoke. It never even popped the fuse, which doesnt make sense to me at all, but that’s what happened. So we disconnected the battery, and pulled the dash out to find that about 30 percent of the bulk harness was melted together. So from here, now we decide if the truck is worth putting a new bulk harness in or not. He still owes over 3 grand on the truck and know he wont be able to get that out of it if he sells it. So is this something that would be a good idea? Or is there a possibility there is still an issue somewhere else that is causing this harness to melt like it is?

What bothers me is a feature that disables the seat belts when the vehicle experiences a electrical system failure.

With battery disconnected can you pull out the seat belts?

If the seat belts need power to them to be pulled out this could make replacement difficult,have you had a look at the schematic? what does it show happening at the seat belt retractors?

Maybe the wiring to the switches in the seat-belt retractors that determine if the seat-belts are pulled out or not melted along with the switches. The melted switches might now be jamming the retractors. It’s a long shot, but it makes more sense than seat-bealts that require electrical power to be pulled out. It’s a good thing that model didn’t have explosive seat-belt tensioners.

You made a mistake when you caused a dead short by touching those wires together. Use a trouble light next time so you can have some resistance or use a meter. I’m sure that the wires melted together because of a dead short that you caused. The seat belt retractors were damaged before that, so you don’t get the blame. Haynes manual says nothing about GMC Sierra seat belt retractors. Troubleshooting says to shoot when trouble is found. Big help that was. Still nothing about seat belts.

That automotive electrician sounds better, and better, to me; but, of course, what do I know?!