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Hi all,
Got a 69 cutlass S and during the course of switching all the interior lights to LED noticed a courtesy light under the steering column with a broken bulb. Have the same one under the glove box. After pulling the busted bulb and replacing with an LED the fuse blew immediately. Socket looks good and the other side has no issue with the LED bulb so wondering if this was an issue for these cars before I dig deep.
Thanks in advance
If what Eric suggests isn't the culprit, there is/was most likely a reason someone left both courtesy lamps/sockets dangling, since this was not a designed "feature" - most likely a known issue someone failed to resolve - a short most likely. Both of those courtesy lamps/sockets are super simple to trace/follow & resolve if you have known good sockets & lamps. You simply need to get under the dash and trace the wires. Using a circuit tester test light is the easiest method to find which wire may be the culprit.
How do you know there is no power going to any of those wires? If you have power to a wire which is not supposed to have power wouldn't that imply you have power to a wire which is not supposed to have power? At this point, there is no manner, as yet, in determining what any wire on those sockets are attached to. Therefore, if the fuse has been removed and you're still getting power to that wire (circuit) then you have an issue. IOW, that wire should not be hot (w/ the fuse removed) but, instead you are getting power to a wire which should not be getting power.
Are you sure you put the correct bulbs in? The courtesy lights use a bulb with 2 contacts not just one. This is so the negative signal coming from the door jam switches can be used to turn the light on. If you installed a bulb with a singe contact, it is likely touching both terminals in the housing which will blow the fuse.
Thanks all, yes I do have the correct bulb cross referenced them. And the other light under the glove box work fine. I will get out my testers out next weekend and trace the circuit see if I can find the short. Just checking for a known problem before digging in.
Appreciate all the feed back.
Thanks all, yes I do have the correct bulb cross referenced them. And the other light under the glove box work fine. I will get out my testers out next weekend and trace the circuit see if I can find the short. Just checking for a known problem before digging in.
Appreciate all the feed back.
the underdash courtesy lamps are a add on option. The main power feed plugs into the fuse box (orange wire) the ground trigger (white wire) plugs into a connector under the glove box.
You should be able to completely remove the harness and inspect it for damaged wires.
how do you know there is no power going to any of those wires? If you have power to a wire which is not supposed to have power wouldn't that imply you have power to a wire which is not supposed to have power? At this point, there is no manner, as yet, in determining what any wire on those sockets are attached to. Therefore, if the fuse has been removed and you're still getting power to that wire (circuit) then you have an issue. Iow, that wire should not be hot (w/ the fuse removed) but, instead you are getting power to a wire which should not be getting power.
Evidently in my ill attempt, what I was attempting to suggest was this. Let's say one of the wires to the socket is already "hot" (energized). With no bulb in the socket, you have no completed circuit to the fuse; albeit, the fuse won't blow since the socket (without a bulb) is an open circuit. You insert a bulb into the socket which completes the circuit but the fuse blows instantaneously when you closed the circuit inserting the bulb. How do you the other wire into the socket is not already "hot" (energized)? If the other wire into the socket is already energized (hot), you could be back-feeding a hot wire (which should not be hot) into the socket? This could happen under a couple conditions: (1) The incorrect orange wire (which should be separate for the courtesy lamps) or (2) the ground wire could be shorted out to a power wire (somewhere). What I'm saying is you have two wires, both are hot feeding into the socket where one should be ground (white) the other hot (orange). When you insert the lamp/bulb - bam, the fuse blows - feeding two hot wires into the same socket the fuse would not blow until you complete the circuit when the bulb is inserted thereby completing the circuit. Doesn't this make sense? I obviously am not attempting to know which wire(s) the OP is contending with, but my first attempt would be to determine if both wires feeding that socket are hot; and, if both wires are hot, which one is the correct one?
Two hot wires touched together would not blow a fuse. Voltage is potential difference meaning more elecrons (-) vs. less electrons (+). With no potential difference there is no current flow. No current flow and no blown fuse. Touching two + wires together (assuming they are both full battery voltage) would be no different than touching two - wires together. In both cases the wires are at the same potential. Think of it this way. take a short piece of wire and touch one end to the positive terminal of the battery, then take the other end and touch it to the same positive terminal of the battery; no potential difference = no issues, sparks, heat, fire, etc. If you take that same wire and touch the negative and positive terminals of the battery you will get a very different result (please do not try the second example).
Interesting tidbit for those unaware: As car guys, we tend to think of circuits as having a current flow from + (hot) to - (ground) known as conventional flow theory. However, from an electronics engineering or physics/ chemistry point of view it is just the opposite. The amount of valence electrons in one area compared to those in another area is what produces voltage (potential difference). As unlike charges attract just like the poles of a magnet if you have enough voltage (electrical pressure) to overcome the resistance between two points, electrons start moving from - to + and you get current flow (electron flow theory). This occurs because electrons repel eachother (- charges) and are attracted to the empty spaces on the valence shells of nearby atoms (which are less negative and as such have a net positive charge compared to the atoms with more valence electrons).
Last edited by Loaded68W34; March 28th, 2022 at 05:40 PM.
Gotcha - You're correct, no potential difference, I should have thought of that. Thank you for pointing that out. What do you think is going on? A ground short where one of the hot wires is creating a potential difference? I'm not sure if the sockets are mounted or if they're outside of the mounting holes themselves where the sockets are held into the metal dash underneath the dashboard. It's solid metal where the sockets attach.
Yep, you're correct in your discussion and I follow. Historically circuits were designed as positive to negative, but that is not true when you examine electron flow - which in a vehicle operating on a DC voltage battery electrons always flow from the anode (-) negative terminal to the cathode (+) positive terminal. I sometimes forget about the actual "potential difference", good on pointing that out.
Interesting tidbit for those unaware: As car guys, we tend to think of circuits as having a current flow from + (hot) to - (ground) known as conventional flow theory. However, from an electronics engineering or physics/ chemistry point of view it is just the opposite. The amount of valence electrons in one area compared to those in another area is what produces voltage (potential difference). As unlike charges attract just like the poles of a magnet if you have enough voltage (electrical pressure) to overcome the resistance between two points, electrons start moving from - to + and you get current flow (electron flow theory). This occurs because electrons repel eachother (- charges) and are attracted to the empty spaces on the valence shells of nearby atoms (which are less negative and as such have a net positive charge compared to the atoms with more valence electrons).
You're going to get into deep doodoo discussing valence shells.
Gotcha - You're correct, no potential difference, I should have thought of that. Thank you for pointing that out. What do you think is going on? A ground short where one of the hot wires is creating a potential difference? I'm not sure if the sockets are mounted or if they're outside of the mounting holes themselves where the sockets are held into the metal dash underneath the dashboard. It's solid metal where the sockets attach.
Personally, I think the wires are touching in the socket or the orange wire is touching something metal near the socket. The pins could be bent causing the terminals to touch only when the bulb is in, or there could be bare sections of wire just above the pins so that once the bulb is inserted the wires are touching eachother (or it could just be a bare section on the orange wire touching metal once it is pushed up out of the socket by the bulb). I think pictures would really help at this point. Socket pulled down away from the dash with a few pics showing bulb in and bulb out.
Seabass,
For some serious questions. With the socket hanging loose from the dash and the interior lights off (door jam switch pushed in) does the fuse still blow when you put the bulb in? If not, does it blow with the lights off (door jam switch pushed in) and the socket back in the dash? If you are testing this by yourself, it will probably be easier to remove the fuse, install the bulb, push the door jam switch in, and then re-install the fuse.
March 27th, 2022, 07:33 AM
