Idiot and interior lights blink with brake light & turn signal?

So, my little guy has an annoying issue, and I just want to check with you guys/gals to see if this is normal Mighty Max/Mitsubishi operation or if it's something I should look into.

My check engine light is on, and I can cope with that, because it's the idle speed control thing, and it's slightly out of my budget and only rarely causes driveability issues. What does irk me, is that the check engine light (and the e-brake light) flickers slightly whenever the turn signal is on in rhythm with the turn signal, as will the dome light if I have it on, and these lights will also blink marginally when the brake is applied.

I was wondering if this is the nature of the beast, because I recall my father's '91 Mitsubishi Fuso did the same thing. I have the stock 42-Amp (or whatever) alternator, which I laughed hysterically when I heard how low the OEM alternator is!

So is this slight lamp flicker something that is completely normal in these vehicles? The electrical systems are so much less complicated than the hundreds of wires in an 80's GM, there are so few feeds and grounds. I'm willing to get into the grounds if this is abnormal behavior, but of my old man's Mitsu did it, maybe it's normal?

One other possibly related thing, if I have the lights on and I turn the dash dimmer down, my radio will cut off. The radio will also cut off/on/off/on sometimes when the volume is up high - aftermarket Sony running stock dash speakers and a 13-yr-old set of 6x9's, no subs... yet - and the dome light will actually flicker with the music as well when I turn it on. It may or may not be related to a possible cruddy ground somewhere, which is why I included it.

The on/off behavior also happened with some no-name aftermarket deck that came with the truck, running just the dash speakers, but the battery also had 2 dead cells and the truck had been sitting a year, so I didn't think anything of it at the time.

Since then, new battery & terminals, new battery ground cable, new alternator, and I cleaned the fusible link box and oxidation off those terminals. Thinking about running a dedicated ground wire for the stereo directly to the battery, but haven't done it yet.

Yeah, that is actually normal for a lot of vehicles. Some instrument and cab lights barely dim when the indicators are on, other cars seem to glitch badly in rhythm with the indicator relay. The brake lights, head lights and indicators draw a bit of current and it has an impact on the rest of the electrical system (the more accessories that are on, the greater the current draw). As for your head unit issue, check what you are using for a permanent power and ignition feed. Use the factory radio power circuit and fuse to drive the head unit and use the clock circuit for permanent power for the head units' memory (you can run it off the main battery but REALLY make sure you use a fuse in line to protect your head unit). Make sure it has a fuse in line for the permanent power to protect the head unit. Also make sure the chassis of your head unit has a good, solid ground. It has a direct impact on how the head unit performs (Pioneer head units will malfunction and fail without a good ground).

The flicker is normal for these trucks with the stock alternator and battery - be sure your cables have good connections, especially the multiple points where the ground connects to the battery tray, frame and engine block, and the ground strap from the exhaust manifold stud to the firewall. The dimmer issue is due to how the lighting and the radio is grounded through the dimmer - they add resistance to the ground to dim the lights instead of the + side. Disconnect the ground from the harness where the stock radio was and run the wire to a true ground - to the battery if you can.

I think your truck was a disco in its previous life.

You might try sandpapering the ground wire on the firewall, make sure all those contacts are good. There's a couple key ground wires that need to be well-connected (there's one on the trans, too) so take your time and just check all the ground wires.

Someone else on the forum was having a similar problem, and hopefully that person will see your post, and perhaps give you better direction. Meanwhile, don't play any Abba or Bee Gees or the truck might produce a mirror ball, and a John Travolta bobble-head doll appear on your dash.

*NOW* you tell me not to play ABBA or Bee Gees! (Both of which I have listened to successfully without any ill effects - at least to the truck!) Yeah, I'm 36, so I lived through the 80s, and the tail end of the disco era. Nearly anything can be heard emanating from my speakers - ELO, Rammstein, Indigo Girls, Linkin Park, Barry Manilow, Larry Gatlin, DMX. So my truck would be more likely to suffer an identity crisis than most. LOL

When I put my Sony deck in (which has successfully been through 3 previous cars, 2 major collisions, one of which the rear of the deck was exposed to weather for 4 months due to a twisted firewall) I was replacing a crappy aftermarket that was connected to the OEM harness, although to my extreme annoyance, the factory plug was cut off. I'm not sure if the ground that fed the busted deck came from the dimmer harness, I wouldn't be surprised because some people don't check that at all, thinking a black wire must obviously be ground. I just used what the other deck was using without actually checking into it, took the lazy way out!

I've seen many a botched install in Chrysler cars because people remove the actual ground strap from the radio and tap into a random black wire instead.

I'll get back into the main ground harness and check on them, and in the meantime, I'll run a dedicated ground to the deck. If my deck is grounding partially through the antenna, this will clear up radio reception a little. I've already cleaned up the manifold ground and gave the connection points for the negative cable a good scraping when I changed it. But I haven't checked the tranny ground.

Good call about the increased draw with the brake lights and all that. You're absolutely right about that, and I recognized the added draw as the actual issue. I know the juice has fewer actual paths through the vehicle than, say, the 80s and 90s GM vehicles I've owned - and so any voltage drop becomes even more crucial, because it involves more equipment due to less physical wires being used.

I was mainly concerned if the flickering lights were normal for the trucks, since every car has its own specific glitches and ghosts. I suppose if I really want to cut down on the amount of current draw, I could switch to LEDs, and even changing the bulbs throughout the cluster would make an improvement to overall demand on the system. I've already considered that option (since I plan on pulling the cluster to install a tach anyway) but I've been hesitant to pull the trigger on it due to color choice and brightness. I honestly don't know what will be bright enough and easy enough to read, and not sure if I want to keep the factory green or not.

Swapping the instrument lights to LED's will make a minimal improvement on current draw. The main cab light would draw more from the system but it is never on while you're driving anyway (a brighter cab light is nicer though...) My suggestion for the instrument backlighting - match whatever the stereo head unit display puts out. It will look better at night.

The lights flashing is a bad ground wire somewhere. Whats happening is power is running from the flasher through the lamp and into the truck. But the shortest / easy path back to the battery is through the drug light and the parking brake light. There is high resistance in the ground. Cab to frame, frame to battery, engine to cab, bed to frame. Does it flash opposite to the flash of the turn signals. Kind of like a rail road crossing guard?

Geezer: I have 7-color illumination on the deck, so my options are a little more open than some would have. I currently have the deck set to red because other colors kind of kill my night vision, so the radio illumination doesn't distract me. However, the stock green dash is dimmer than I'd like it, most cars' gauge illumination is a little dimmer than I'd prefer. I would like the radio to match the gauges, but if I have to choose between my OCD-everything-must-match and gauge clarity, I'd pick gauge cluster clarity every time. lol

Camoit: The bright-dim-bright-dim flashing of the idiot lights with the turn signal is *not* opposite of the turn signal; leading me to deduce that it is not back-feeding through the dash to ground out. The flickering is that the idiot lights dim when the turn signal comes on, and brightens when the turn signal clicks off. The idiot lights also dim quickly once and then back to full brightness when I step on the brake. Most people might not even notice that it does this; however, I've owned many cars in my life and they've all had similar symptoms but to a much lesser degree. That's why I was asking if this was "normal" for these vehicles and their low-output charging systems. Nothing points to a serious issue or impending doom (at least, not at this point, but since I have some of the world's worst luck, I thought I'd check with experts on these trucks).

However, if this was atypical, it is something I'd like to address as soon as possible to prevent a tow home from work or whatnot. ;-)

Just a quick cursory check of amperage draw in the gauge illumination circuit, using that "old-fashioned" math... Assuming six #194 bulbs are used to illuminate gauges only, the draw is 1.62 amps. Switching to #194 LED bulbs changes the draw to 0.42 amps. That is a reduction of roughly 75%. And if I'm pulling the cluster to swap them out, I'd also do the idiot lights too. Every little bit counts with a 42-amp alternator, right?

Future plans include adding an amplifier and a subwoofer (probably 500-600 Watt, single or double 10" depending on what I can find/build for a box). I'm not trying to blow the windows out, I just need a little of the lower end filled in. Should I add a second battery and an isolator to reduce stress on the charging system?

First up, ditch the 42 amp alternator. The extra load of audio gear on the charging system will actually kill engine performance (I have seen guys running big amps with a stock charging system and heard the alternator belt screaming from being under load :lmao:). I'd be going large - try and source something like an 85 amp alternator. Get a decent battery to back it up while you're at it. A strong charging system is your best friend and often gets overlooked when thinking about performing mods.

look for a 75 to 100 amp alternator - they were stock in starquests and should be easy to find new or rebuilt. Also install a 1000 ca battery, and a 1 farad or larger stiffening cap for the amp. The cap will also get rid of the light flicker when the turn signals flash.