Just won an auction - M1088A1

The turn signals and emergency flashers don't work on my M1088.

I just found the flasher unit:


I tested the flasher box. It flashes with 12v DC hooked up and a test light. I'll clean the connector. Is there something else I should check?

While under the dash, under the passenger kick plate, I found three cables with connectors that were not connected to anything.

What are they for?

All the flasher power passes thru the hazard switch(its powered all the time) the flasher output passes thru the turn signal switch. Here is a condensed lighting diagram I drew once upon a time if the hazard sw gets unplugged the TS wont flash…

The cable should have a metal tag with a number on it, P something… on the schematic, on the first page or 2, most all the plugs are listed… Y0u can use the wire numbers on the plug wires to help ID them also…

Ronmar said:

each cable should have a metal tag with a number on it, P something… on the schematic, on the first page or 2, most all the plugs are listed… Y0u can sometimes use the wire numbers on the plug wires to help ID them…

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Where is the schematic? I get lost in the TMs. If you could give me a hint, I'd appreciate it

well the A1 schematics are in the tech manual section here on SS. Forget what year your truck is?

Ronmar said:

well the A1 schematics are in the tech manual section here on SS. Forget what year your truck is?

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It's a 2003 M1088 A1. I've downloaded all the TMs for the 1083s would it be in there somewhere? OK, I just found the FMTVA1 schematic.

Not as familiar with anything beyond an A0, but that could be harness points for a winch control switches. That harness was an option in the A0, but may have been included in A1 and above applications (my attempt at a semi educated guess?)

there are a couple unused plugs under the pax dash. The trucks use a generic wire harness that supports different options that may or may not be installed in a particular vehicle...

The A1 schematic table is not as complete as the A0(doesn’t show all the Plugs in the list) Message me and I can Email you just the A0 schematic in .PDF form. Between all the versions, the wiring actually stayed very similar with the same breaker plug and relay designations for the most part… Even a lot of the wire numbers remained the same for particular circuits…

You will find MANY unused connectors on every vehicle made in the post-WWII era. The wiring harnesses are built in a modular fashion and connectors are added so that features can be added or subtracted depending on how the vehicle was ordered and in some cases the connectors are supplied for later installation of options - such as when Air Conditioning or Keyless security was commonly installed by the selling dealership prior to delivery - back in the 50's though the 80's and even into the early '00's this was common practice and still is for some features to this day.

On our trucks there is a whole constellation of accessories in the TM's that can be added - everything from radio gear to arctic troop, battery, and engine heaters, etc. Many of these come with wiring harnesses designed to plug into various places on the truck for power and control routing. It is up to the recieving unit command as to which of these features they will elect to install - mission parameters and budget notwithstanding, the troops love added features just as much as folks in the civilian world if they can justify them.

In your picture there - the two-pin Deutsch connector is for the troop 12v accessory outlet - they added those on A1's to stop the troops from cutting their own wiring in for phone charging, etc.

MatthewWBailey said:

I'll send you a bottle of Tylenol. It's the most important , most used consumable during overhauls.

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Alcohol is.

Ronmar said:

All the flasher power passes thru the hazard switch(its powered all the time) the flasher output passes thru the turn signal switch. Here is a condensed lighting diagram I drew once upon a time if the hazard sw gets unplugged the TS wont flash…

The cable should have a metal tag with a number on it, P something… on the schematic, on the first page or 2, most all the plugs are listed… Y0u can use the wire numbers on the plug wires to help ID them also…

View attachment 950574

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The flashers are working now! I have working Hazard lights and turn signals. I did two things: I unplugged the solid state flasher module and sprayed both sides of the connector with electronic cleaner. Then I cleaned up the circuit board using small foam brushes I got all the dust off and the sprayed the board liberally with electronic cleaner There was a LOT of dirt and dust on the board.

I had not yet gotten around to testing the fuses and relays, or checking the contacts for dirt and corrosion.

I did all that yesterday. This afternoon I went out and tried the flashers and they work great! I'm guessing it was the connector to the solid state flasher that was a little dirty. It didn't look bad, but yesterday the flashers didn't work and today they do!

Somehow, automagically, the flashers are fixed!

Very often it's just dirty switch/relay contacts, capacitors that need to reform (radios, etc), and the like. Just USING the vehicle you will often notice that things start working on their own after a little bit of operating time.

GeneralDisorder said:

Very often it's just dirty switch/relay contacts, capacitors that need to reform (radios, etc), and the like. Just USING the vehicle you will often notice that things start working on their own after a little bit of operating time.

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I love automagic repairs