Captain Obvious

Recent discussion on the same issue. Maybe some help in here? http://www.classiczcars.com/forums/electrical-s30/53259-parking-interior-light-fuse-melting.html

Wait a minute... Last I heard, you were driving around with your headlights on and your alternator had failed. Your battery voltage was dropping? "A minute or two later, I was getting 12.8 and slowly dropping. By this time the battery was reading 12.5." When I said that it either works or it doesn't, I meant that there really isn't much else in the whole design that could be an issue with the internally regulated system. Other than a loose drive belt or a bad connection, about the only thing that can go wrong is inside the alternator itself. The only other thing I could come up with is if your CHG lamp is burned out, there's a chance that your alternator won't get itself up over the hump of producing current. But if your CHG lamp works normal, then that shouldn't be the issue. Take it out and have it tested or borrow a known good one if you can and throw it in and see what happens?

Yeah, that sure starts to sound like marketing propaganda aimed at increasing your own sales by torpedoing someone else's product. I used to take my GM to 6000 RPM every once in a while and it never gave me any trouble doing that.

I'll put in a third vote for this. The internally regulated system either works, or it doesn't. You mentioned your charge lamp flashing yesterday... Does it still work today? The CHG lamp should light up when you turn the key to "ON" before you crank the engine. Does it?

Yeah, I grew up on the incandescent as well and completely understand. That whiter than white LED thing just doesn't work for me either. I don't know if it's all mental, or age... But I just don't feel that I can see as well with the cool white shade. The LED bulb I installed is a little whiter than the stock incandescent, but I find the whiter bulb offsets the yellowing old plastic lens of the dome light. End result is that I think it looks like it's "supposed" to look. Original shade, only brighter. Haha! I don't think my hair brained weird stuff I spend my time on is going to scare MSA or any of the other suppliers.

I settled on Part Number: 3710-WWHP6. It's a 37 mm long festoon with 6 LEDs in warm white. https://www.superbrightleds.com/moreinfo/festoon/3710-led-bulb-6-smd-led-festoon/661/. It was a little longer than what fit comfortably between the mounting clips and I had to grind a little off the connector clip fingers in the lamp housing to get it to fit between the fingers, but it's a once and done job, I've very happy with the outcome. Brighter and not harsh. Hot the "specifications" tab and you can choose what color you want. Lots of people like the "cool white" color, but I'm not one of them. I find the bluish "cool white" light harsh. I bought "warm white" and I love it. Here's some pics showing what I had to do to the mounting clips to get the bulb to fit. I used a carbide burr on a dremel. Don't get tiny brass slivers stuck in your fingers (or eyes): And even though you can't tell much because there's nothing else to compare it to, here's the obligatory "ON" pic: If you don't want to deal with modifying the clips to get the wider festoon to fit, you can sacrifice some brightness for ease of installation and get a 4 LED shorter version instead: https://www.superbrightleds.com/moreinfo/festoon/de3175-led-bulb-4-smd-led-festoon/238/1129/ Part number 3022-WWHP4 is the shorter 4 LED version in warm white. Lastly, I don't think you're going to find a "warm white" shade at a generic AP store. Seems most people like the bluish LED color of the "cool white" bulbs and that's all I've ever seen on the shelf. So if you want cool white, you might be able to find it local, but if you want to control the shade, you'll probably have to mail order it.

Gotcha. Step 0 - Buy or borrow a meter. :paranoid:

Well I sure hope that's truly the issue and don't want to rain on any pre-parade celebration, But... Your fuel filler cap is supposed to prevent vaccum buildup in the fuel tank. Shouldn't really matter if those lines were blocked off or not (unless you've got a non-venting fuel cap). I mean, I wish you the best here, but don't want you thinking you've found the smoking gun. Yet. Don't shoot the messenger?

And the problem BETTER go away once the speedo is disconnected! The dimmer control gets it's wires from the speedo, right? If the speedo is disconnected, so is the entire illumination control circuit? So what are you gonna do once everything (except the speedo) is disconnected and the problem still occurs? :ogre:

I know the 74 was transitional in spots, but according to the wiring diagram, your hazard switch DOES have a light on it. Either your bulb is burned out, your connectors are corroded, or maybe that's where your problem is originating. And about the other three... Defogger, Choke, and Seat Belts? None of them are controlled by either the dimmer or the combo switch. All three of those will always be full bright when their respective switch is turned on regardless of the position of the dimmer or combo switch. For example, the CHOKE indicator will come on full bright anytime the choke lever is pulled regardless of the combo switch or dimmer positions. Nothing is impossible, but it's unlikely that any of those have anything to do with the problem you are having. If I were you, next thing I would do would be to disconnect the hazard switch and see what happens. And you've been disconnecting things one at a time and then what? Reconnecting them or leaving them disconnected? If you've been reconnecting them, I wouldn't do it that way. I would disconnect something and leave it disconnected until you get to the bottom of the problem.

And I'm not sure if this is the most appropriate place for this, but since it's related... While reviewing the wiring diagrams for the 260, I turned up a couple mistakes. I don't know if these are old hat already known issues, but since I'm not the keeper of 260's electricals (Steve?) I thought I would hand off to the experts. Here's a portion of the 260 (manual trans) diagram: Here's what it should look like: If there is a collective "Problems Found on the 260 Wiring Diagram" thread, this could go there. If there isn't a thread like that already, maybe one should be started? I know I've got at least one other 260 problem that I've discovered.

boosd, SteveJ summed up the problem when he said that the Green/White wire is somewhere shorted to the Red/Blue wire. Problem is figuring out where that short is. Here's one idea that might help track it down: Park the car in a dark spot (dark garage or just wait until it's dark out). Turn the dimmer control to full dim. Turn the combo switch to the first position (turn on the parking lights). The parking lights should all be lit and the fuse should not be glowing. Then quickly turn the dimmer to full bright and look at your interior illumination lamps. Don't keep the dimmer full bright for long because you're going to pop the fuse or burn something up again. But quickly look at the following: speedo tach water/oil amp/fuel clock lighter heater control panel radio hazard sw If you can't look check all of them in a second or two, just turn the dimmer back to full dim and give it a minute or two for everything to cool off. After a cool off period, do it again to check the stuff you didn't check the first time. If any of those devices are NOT lit, I'd start there.

Steve, Haha. Yeah, that's one of the things that gives me trouble with distance diagnosis. That and the ability to explain things in a way that others understand. It might make sense in my head, but being able to convey that info without writing a novel is a different story! I found the same thing as you did with the buried splices. I'm planning some electrical upgrades (like headlight and starter relays) and have dissected a cadaver engine compartment harness for investigation. They did the same thing there. Splices crimped and taped and then buried in the outer layer of tape. Just hoping the fault isn't buried...

Yup. That's what I'm thinking. The thing that worries me the most though is that all of this started after some melties happening. I just hope it isn't melted insulation buried down in the harness somewhere. If it's a bulb, even I could probably find it. However, if it's melted and shorted insulation somewhere in the harness, I'd need one of those RF signal sniffers.

Maybe it's just me, but I'd much rather have that 280 than that series 1 barn find (maybe hit in front maybe not?) that's on ebay for stupid money. That 280 is fantastic. I still don't think I'd pay 25K for it, but it sure is beautiful.

The pot doesn't go OFF-ON instead of gradual. He's got a very low resistance connection somewhere between the output of the pot and ground. That connection is sinking away most of the current through the pot and only a small amount goes through the illumination bulbs because their resistance is higher than whatever is shorted. (Think voltage or current divider between the short and everything else.) So when the pot is cranked to full brightness, there's just enough current through the bulbs to get some light out of them even though the improper connection is sucking down most of it. But when you start cranking the pot away from full brightness, the current drops and the bulbs go dim. Bulbs are still passing the same percentage of the total current, but it's not enough to glow the filaments. Even with the pot turned a little off full bright there's still lots of current flowing through the pot (too much in fact), but not enough to glow the filaments or blow the fuse. At least that's my read... Electrical troubleshooting is very hard from afar!

I don't think it has anything to do with the parking lights. He said he disconnected all of them and the problem persisted. He also said that he can crank the dimmer all the way down and the fuse doesn't pop. It's got to be something powered by the dimmer rheostat.

Not sure what's going on, but tossing out some stuff to think about. How do you get a continual rich condition? - Nozzles not adjusted properly - Shouldn't be rich at 2 turns down (assuming nothing is worn out). - Float level too high - You checked this and it's OK - Float needle being overpowered by the fuel pump - You got a 3 psi regulator - Nozzles getting stuck down instead of returning fully up - You checked this and it's OK - Needles not installed correctly in the pistons - You checked this and it's OK - Pistons getting stuck and not rising properly - You checked this and it's OK How do you get a transient rich condition upon startup? - On a hot shutdown, you boil the fuel in the bowl and as it percolates, it bubbles up past the needle and into the carb throat and then runs into the intake manifold. - After you shut down, you slowly overpower a slightly leaking needle valve(s) with residual fuel pressure in the rail. The pressure in the stock rail and pump system drops to zero when the engine stops, but with your electric pump and a regulator, I don't know how you have it plumbed. If you're applying three PSI to the needle valves even when the engine is off, you might have a small leak in one or more of the needles that isn't a big problem when the engine is running and consuming gas, but might be an issue when the engine is off.

Very nice! Are you gonna rattle can the block or you got more elaborate plans for that?

The problem is in the dash illumination light section, but it's not the dimmer switch, it's somewhere else. Something in your illumination lamp section went almost short and is hogging current. It's not a dead short, but almost. It's not the dimmer itself. It's not the parking lights. Maybe one of your illumination bulbs in one of your gauges failed short? Could also be the illumination bulb in the hazard switch or the heater face. Maybe ash tray lamp (if you have one - not sure when they added that). I'm thinking that either one of your small illumination bulbs went short or you pinched or melted a wire somewhere behind the dash. Was everything working fine before you burned up (and then replaced) the first combo switch?

Excellent. Either a little tighter on the current banjo washers or going back to the old washers then. Even though the bowl gasket has been cleared of issues, I do have one more thought about that part... I was originally thinking the same thing, and that's why I asked the question. But after I asked the question I started thinking that it probably wouldn't really matter. The fuel level may be below the level of the bowl gasket when sitting static in the garage, but as soon as you hit the road and the fuel in the bowl starts sloshing around, that gasket is going to be completely bathed with fuel pretty much all of the time even if the bowl level is correct. So the bowl gasket has to be a positive seal even if the fuel level is correctly below the level of the gasket. In other words, you can't get away with a poor bowl gasket even if the fuel level is at spec.

If you did the float level on the car I have confidence in the results. I've never experienced the bowl gaskets leaking with new gaskets. They always seemed to do a good job of sealing. I guess it's possible that there is some flaw in the bowl lip or cap sealing surface that the old gasket was able to compensate for, that for some reason, the new gasket cannot? I have seen the banjo washers leak though. I solved that problem by simply loosening them up a little and then cinching them up again (maybe a little tighter than they were last time?). Failing that, you could try reusing the old metal washers. I wonder if maybe what you think is a leaking bowl gasket is actually fuel spreading from the banjo bolts and the bowl gaskets are not really leaking? Gas, being thin and volatile, spreads rapidly...

Did you do the clear line check on or off the car? If you did it off, I would recheck it on the car. You used new bowl gaskets and banjo washers?

Happy Thanksgiving to the Great White North!!

That's so cool! I did some distance learning from the same institute. I've got my Sheet Harbour Institute of Technology Hardware Engineer Associates Degree.