mikekaz1 Posted October 2, 2015 Share Posted October 2, 2015 1991 Comanche (obviously). HO-4.0/AW4 Started happening about 2-3 weeks ago now. Battery will die over night/ extended periods ~6-12hrs. Is there any common power drains associated with these trucks? I've swapped batteries with another truck I have. And problem stayed with the Comanche. So its not the battery. I also tried replacing my ignition switch (not tumbler) as that was also a known issue for other problems I was having (won't run starter, radio losing memory, ect). And that seemed to fix it (day or two of starting ok in the morning) but problem returned and battery was under 9v and wouldn't start again. I plan on getting a DC amp clamp this weekend to measure my positive lead and try and fuse out legs to track it down. But just curious if there is common draw components. Link to comment Share on other sites More sharing options...
87MJTIM Posted October 2, 2015 Share Posted October 2, 2015 Have you recently done any electrical modifications? Perhaps a new/diff radio. I suggest this because some radios draw a lot of power to keep station presets and clocks. my 2¢ I saw a video on youtube how to test for parasitic draws. Hook a DVOM up to the batt. See how much current is flowing. Then start pulling fuses to see when the reading drops. That circuit is were you start your search. Link to comment Share on other sites More sharing options...
Lee21490 Posted October 2, 2015 Share Posted October 2, 2015 Have you recently done any electrical modifications? Perhaps a new/diff radio. I suggest this because some radios draw a lot of power to keep station presets and clocks. my 2¢ I saw a video on youtube how to test for parasitic draws. Hook a DVOM up to the batt. See how much current is flowing. Then start pulling fuses to see when the reading drops. That circuit is were you start your search. This. Had the same issue when i first got my mj. Turned out to be the fuse for the "Rear window defrost" P/O Swapped the whole fuse box out of the parts xj he used for the motor swap. :yes: Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 2, 2015 Share Posted October 2, 2015 A couple of XJ/MJ causes of parasitic amp draw I've experienced is the light staying on in the glove box due to a sticking switch, and also in a vanity visor due to another sticking switch. Normal amp draw reading with an ammeter in series with the battery positive terminal for our rigs with everything shut down is ~90ma. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 3, 2015 Author Share Posted October 3, 2015 OK so I did some investigation. Put my meter in series with the positive battery cable on 10a. And I was pulling about .23a. As soon as I unplugged the fuse panel maxi fuse it dropped to 0a. So I went off to the fuse box. Unplugged everything and started replacong fuses till the amp draw returned. Found to be accociated with the "dome light" circuit. As soon as that was added/removed I gained/lost the .23a. So I tried unplugging both done lights. Didn't help. Tried unplugging both door switches. Didn't help. Also found that the dome light fuse controls power to the clock and radio.... but both clock and radio have their own fuse. But can't understand why? Radio fuse and clock fuse both disable just themselves. But dome fuse cuts all three (dome, clock and radio) how or why is this? I don't understand it Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 3, 2015 Author Share Posted October 3, 2015 Have you recently done any electrical modifications? Perhaps a new/diff radio. I suggest this because some radios draw a lot of power to keep station presets and clocks. my 2¢ I saw a video on youtube how to test for parasitic draws. Hook a DVOM up to the batt. See how much current is flowing. Then start pulling fuses to see when the reading drops. That circuit is were you start your search. Radio is a used unit. Installed about two months ago. This problem is only 2/3weeks old tho. Link to comment Share on other sites More sharing options...
87MJTIM Posted October 4, 2015 Share Posted October 4, 2015 It was mentioned prior, check the glove box or vanity mirror. The 88 electric FSM has the floor lamp, B pillar lamps, cargo bed, and glove box are all fed from the dome fuse. This is hot all the time. The vanity (passenger visor) and cigar lighter getting power from both the dome and radio fuse. This fuse only is hot when in Run. Do you have the cargo box light? The cargo lamp is powered by the switch on the dash. It has an LED to show when it is turned on. It the switch is bad, the light my be on all the time. In a dark location, like a closed garage or "a dark and stormy night" sit inside the truck and look for any lights on. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 I tried leaving the glove box light out. Didn't help (I changed all interior bulbs to LED anyways). Cargo light is not factory. (On its own circuit) So I know that's not it. No floor lights on this model. And both b pillar lights are unplugged. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 I pulled the dome fuse just to double confirm my meter reading and diagnosis. But I also swapped my battery for a marine deep cycle. So we will see if that helps. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 4, 2015 Share Posted October 4, 2015 Have you unplugged your radio? Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 That's one of my next tests. I'm waiting tonight to see what happens with the whole dome light circuit unplugged. If I have juice tomorrow I know ive found it. And then I'm going to single out each thing from there. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 I'm just kinda puzzled on the power wiring. Why have independent clock/radio fuses if they are all controlled by the dome fuse. Also possible culprit (but sceptical as problem didn't start at the installation) there's a faint red light behind my radio dial (not whole thing) that stays on all the time. Now when I pull the radio fuse this stays lit. But when I pull dome light this red light turns off.... no idea why or how. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 4, 2015 Share Posted October 4, 2015 Most all radios, CD players, etc. have a non-switched 12V constant input. For sure the stock radios in our trucks do. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 Just found a semi-decent fuse chart. So the dome fuse holds the memory power (constant?) and radio fuse is the ignition power (switched?). Correct me if this sounds wrong. http://jeep.zerok.ru/index.php?page=105&word=dome+light Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 4, 2015 Share Posted October 4, 2015 If you are referring to your 91 the pink radio harness wire is 12V constant and the VIO/WHT wire is switched 12V. Anyhow, if your battery is alive tomorrow, unplug the radio and check the draw again.. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 Yes My 1991. I checked radio wiring again today. If I recall correctly the radio side has yellow wire constant(memory) and red wire switched (power). Which I had/have going. Yellow-pink red-purple. So that should be correct. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 well with the dome fuse out all night i stayed well above 12v on my battery! and fired right up, so it's definitely in that circuit. I'm thinking it has to do with the radio. its a "dual" head unit. I'm going to call their customer support tomorrow and question them on that backlight staying on and if its supposed to be there or not. Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 4, 2015 Author Share Posted October 4, 2015 also, on a side discovery. my drivers door switch for the dome lights never worked. in searching for this problem i found that the wires on the back of the switch have fallen off into that body cavity.... is there any easy way to retrieve these wires? Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 6, 2015 Author Share Posted October 6, 2015 So left the fuse in last night. And come 7pm tonight when I went to turn it on. BAM 12v and formed right up. Even with the dome circuit powered.... I'm going to monitor it still the next couple of days. But I guess its possible I had two failing batteries...? The original one was a very old and undersized battery. So honestly not surprising. The next was only 3/4yrs old originally from my TJ but in my s10 for the last 2 years and fully reliable the whole time in that (but also a standard 4banger). But this marine battery I inherited seems to be doing better. Also talked to dual electronics and they said its suppose to glow red. So should be OK I guess Link to comment Share on other sites More sharing options...
mikekaz1 Posted October 8, 2015 Author Share Posted October 8, 2015 yep I guess it was just the batteries.... as its been good since the third battery. thanks for everybody's input!. Link to comment Share on other sites More sharing options...
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