Thermal Flasher self-destruct

[Sunfamily267]

I did something to make the Thermal Flasher self-destruct…TWICE. (searched the forum for Burnt Flasher, Flasher, exploded Flasher...but did not find one related to my issue. If there is one, please forward to me. thanks.)

I have a 1999 M1097A2. Working on it for the past couple months off-n-on getting it road legal.

Situation:
Before replacing the Flasher, most of the incandescent lights were blown or not working. I checked the turn signal switch using TM 9-2320-280-20-1; pg 2-396-397. Ops Check good. I also checked for 24V on 325A (Pin A of Flasher cannon plug) while the turn signal was in the Left, Right, and Hazard positions. G2G (24.6V). I checked for a good ground on 57K (Pin C of Flasher cannon plug). G2G.I replaced the incandescent turn signal/running lights with LED bulbs and replaced Thermal Flasher NSN 5945-00-789-3706 with NSN 5945-01-584-9793 (works with LEDs and incandescent bulbs). The new flasher was not mounted, I just let it hang, I ops checked turn signals and hazards and all G2G. All the lights were working.

At the time of the Ops Check:
- Engine was off, just using battery power.
- The flasher was not permanently mounted, just hanging
- The battery was connected through a disconnect I installed on the negative side
- The Transmission 12V power was disconnected from battery and the 12V line from the Alternator disconnected. This was just because I was working on those items related to a separate task.

A few hours after the turn signal Ops Check, I was ready to check a few more things:
- I mounted the Flasher properly
- connected the Transmission 12V cable to the battery, yes to the correct battery terminal.
- connected the Alternator 12V cable to the battery, yes to the correct and same terminal.
- Closed the hood
- Engine is off

Not sure if this is related to the issue but when the 12V alternator cable is connected and the disconnect is open/off, I have a residual 3.3V floating.

So, I closed the disconnect and turned on the Lights (Serv. Drive and Dim). Lights all worked fine. Moved turn signal to Left position and went to check front signal, POP! and then the lovely smell of burnt electrical. Several bad words announced since this was the second one I blew-up, I thought I found the issues before (corroded bulb and bad wire...thinking these may have led to a short)

Hard to see in the picture but one of the 3 leads on the transistor is broken which I assume was the one with the juice on it to make it blowup.


Anyone else experience this? What was it and what was the fix?
Been trying to figure it out for a week now but stuck. Well, that is it. Can’t really afford to keep blowing these things up while troubleshooting. NaFC

Thank you for reading to the end. Please don't ask me why I changed to LEDs or "Why you did this or that..." Just some helpful hints on how to move forward if any ("did you try this or that...), Much appreciated!

 

[Mogman]

Welcome to the forum!!
When you disconnect the ground with the switch and you have any load at all on the 24V circuits you reverse polarity the 12V circuit.
You need two disconnect switches, one on the ground and one on the 12V connection to the batteries.
I can't see how this would kill the flasher but it is definitely bad for the 12V items IE the TCM and regulator.

 

[Sunfamily267]

Welcome to the forum!!
When you disconnect the ground with the switch and you have any load at all on the 24V circuits you reverse polarity the 12V circuit.
You need two disconnect switches, one on the ground and one on the 12V connection to the batteries.
I can't see how this would kill the flasher but it is definitely bad for the 12V items IE the TCM and regulator.

Copy. That's what I thought I'd have to do get rid of the 3.3v floating around. Agreed, I don't think this is related to the flasher issue. Something is shorting it, I think.

 

[Mogman]

Copy. That's what I thought I'd have to do get rid of the 3.3v floating around. Agreed, I don't think this is related to the flasher issue. Something is shorting it, I think.

I would put a fuse wired in where the flasher goes and make sure you do not have a short, of course the lights will just stay lit instead of flashing.
There are others with allot of experience converting to LED that will surly jump in and help.

 

[Mogman]

You could also wire in a 24V headlight across where the flasher goes if you have one laying around, the turn signals should not pull enough current to light the headlight but a short of course would, this would make looking for the short easier and cheaper than a pile of fuses, you would instantly see when you run across the "short"

 

[Sunfamily267]

I would put a fuse wired in where the flasher goes and make sure you do not have a short, of course the lights will just stay lit instead of flashing.
There are others with allot of experience converting to LED that will surly jump in and help.

Fuse idea sounds like a plan for troubleshooting and I have a couple old headlights I swapped out too. I should be able to rig something up. The Flasher (transiter) just opens and closes (blink, blink, blink....) 24v on wire 325A; Pin A, correct? What is really getting me is that this circuit could not be any simpler. 24v to it, ground for internal use, 24v out.

 

[Mogman]

Yes it is in/out on 325A/B not sure which way but for troubleshooting with a (EDIT, incandescent) headlamp for example the polarity does not matter, I would think it does matter how you connect the flasher itself.

 

[Sunfamily267]

Yes it is in/out on 325A/B not sure which way but for troubleshooting with a (EDIT, incandescent) headlamp for example the polarity does not matter, I would think it does matter how you connect the flasher itself.

just an update...I have not T/S the flashers yet...I do have the pieces now to continue that T/S. I did buy a different Flasher Relay that was $16 and works with 5v-30v DC @ 10A and some inline fuses. Plan on doing the headlamp and trick with fuses first though.
However, the fun continues. I was cleaning up my mess to start it after some fluid changes, transmission work (replaced relay and trans light), installed a back-up switch for new B/U lights, and a few other minor things. Went to start it, "Wait" light came on as usual, and when I moved to Start a nice BLUE flash and welding sound came from the Positive Buss Bar area (wife was watching from a distance and saw it). That is a new issue. I assume I caused that issue somehow because it didn't do that the other 10 times I started it in the past (pre-a lot of cleaning, wiring, and R/R of some pieces). Researching it tomorrow to see if I dropped something by the starter or near the buss bar. Just went for a walk after that last disappointment.

 

[Mogman]

just an update...I have not T/S the flashers yet...I do have the pieces now to continue that T/S. I did buy a different Flasher Relay that was $16 and works with 5v-30v DC @ 10A and some inline fuses. Plan on doing the headlamp and trick with fuses first though.
However, the fun continues. I was cleaning up my mess to start it after some fluid changes, transmission work (replaced relay and trans light), installed a back-up switch for new B/U lights, and a few other minor things. Went to start it, "Wait" light came on as usual, and when I moved to Start a nice BLUE flash and welding sound came from the Positive Buss Bar area (wife was watching from a distance and saw it). That is a new issue. I assume I caused that issue somehow because it didn't do that the other 10 times I started it in the past (pre-a lot of cleaning, wiring, and R/R of some pieces). Researching it tomorrow to see if I dropped something by the starter or near the buss bar. Just went for a walk after that last disappointment.

It's ALWAYS something!!!

 

[Sunfamily267]

It's ALWAYS something!!!

A good update.

So, T/S the flasher again, couldn't find any anomalies, shorts, or anything unusual. I did not use wire 57K as my ground, I connected a new ground to the chassis and checked it for continuity, G2G. The headlight test worked fine and came on as expected with all wires connected and turn signals in L & R. I replaced the headlight with a non-OEM Flasher Relay I bought for $20 and used a voltmeter to check the blinking side, G2G. I connected the new Flasher Relay and inline fuse to the turn signal lights and all blinked...G2G. Not sure what the issue actual was but I eliminated the ground 57K and the OEM Thermal Flasher, and all worked fine. The OEM Thermal Flasher that I ordered three times (2 exploded, 1 being returned) from Midwest Military Equipment said it was the one that works with LEDs or Incandescent bulbs but the NSN ended in 3706 vice 9793. From what I read NSN ...3706 is for incandescent bulbs. I do not think that was the issue that caused the initial self-destruct though. Anyways, It is working now.

2nd issue, The Blue Flash during starting...that was a loose nut on the Positive Buss Bar just enough space between the nut/washer and the solid buss bar to cause an arc. That also fixed an early starter issue (starter would engage but then spin freely...didn't have the juice to stay engaged fully).

Today was a good day! A lot of issues resolved. Did a driving test and almost everything is working as it should. No more Limp Mode either. Transmission is working normal now after replacing the relay and some broken wire issues. The Trans Light stays on, but I'll search the Forums for that. I've seen many about that.

Thanks for the T/S advice.

 

[Mogman]

Great job!!
That is still strange that the OEM flashers blew up like that, at the end of the day if you have working flashers that is all that matters!!!