Mystery Dash Switch in 1986 M998

[Phoenix77]

Yes; I looked in the TMs. No, it isn't depicted.

Only thing I can guess this might be associated with is the generator throttle handle (i.e., power feed on / off).

Anyone know what this does? Yes, I've messed with it with truck on & truck off...

Thanks in advance.

 

[Retiredwarhorses]

Most of the time for an IR lamp...

 

[donquijote]

On my rig... it controls the flashing beacon light.

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[Phoenix77]

I have a blackout light on the light selector to the left of the switch.

Might have been for a flashing light... This was a Ft. Bragg resident, and I surmise the 88k miles to be original and exclusive to on-base.

Maybe an MP HMMWV...

 

[Phoenix77]

Just traced the wire farther; went out to engine compartment and has power spliced off the light switches. Probably an IR light, as @Retiredwarhorses noted.

Perfect for my use, since I am installing two (2) supplemental fans under the grille to help keep the operating temp down.

Just need to verify 12v or 24v before connecting.

 

[Retiredwarhorses]

Just traced the wire farther; went out to engine compartment and has power spliced off the light switches. Probably an IR light, as @Retiredwarhorses noted.

Perfect for my use, since I am installing two (2) supplemental fans under the grille to help keep the operating temp down.

Just need to verify 12v or 24v before connecting.

save your money, fans are worthless and do more to increase temps due to blockage.
This has been covered for about 30yrs..

 

[Milcommoguy]

If all of the cooling system is up to snuff... one shouldn't be overly concerned with an over temperature condition. If cooling system can not maintain the +/- 190 to 220 degree range with system cycling as need, time to look into problem. (my experience 6.2L, other engines / configurations user have noted a little warmer)

Ditto the electrics. IMO one would be hard pressed to move / augment the air designed into the system with an electric motor. This system has about 8 ponies of air flow.

Here in the Mojave Desert with outside temps in the 120's easy... and anything in the sun is untouchable, my truck as never shown an over temp condition. That was after a couple of system flushes. Was full of junk and rusty crud. Replaced all the easy to get at components, T stat, T switch, Cad valve, hoses, cap, etc. (I like to know it's fresh and new) Use distilled water to slow the gunk build up.

Hot tip is to check the system for proper operation / cycling, clean the crud out of system and between the radiator stack (bugs and leaves) bent fins. Kinda like another PM step to Humv ownership, right after all the fluids, spindles, brakes, lights, rattles and squeaks.

AND that's the cool tip from here, CAMO

 

[papakb]

Probably the best thing you can do to improve cooling is to remove the armored grill if you have one. If not then like Cam says, make sure everything is in proper working order and you'll be OK.

 

[Crapgame]

On my rig... it controls the flashing beacon light.

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For RAWL Rotating Amber Warning Light, all our vehicles, from M1025 HMMWV to M125A2/M106A2 Mortar Tracks had them in Berlin.

 

[Phoenix77]

I did a full cooling system flush when I first got the M998. It will get to 220° and the fan kicks on as long as I am moving.

I switched away from the armored grille and it helps. If I'm creeping along in a parade, the fan doesn't kick on, and it will go north of 220.

These fans are to bring it down in those instances.

 

[Spitfirebuilder]

I used that switch for some fog lights. I installed an indicator light above it.

 

[DREDnot]

I did a full cooling system flush when I first got the M998. It will get to 220° and the fan kicks on as long as I am moving.

I switched away from the armored grille and it helps. If I'm creeping along in a parade, the fan doesn't kick on, and it will go north of 220.

These fans are to bring it down in those instances.

I would use that switch to manually turn the factory fan on. I added a switch to mine that just breaks the circuit between the temp switch and the fan control module. fan runs continuously and cools things down even in AZ heat in traffic

 

[Milcommoguy]

I would use that switch to manually turn the factory fan on. I added a switch to mine that just breaks the circuit between the temp switch and the fan control module. fan runs continuously and cools things down even in AZ heat in traffic

If cooling system is working correctly, cycling as is should... what would the need for a bypass / over ride switch. Worst case hot or broken it should run.

Hear in the Mojave Desert, highway or trail never worried about over temp condition. I note... any sludge up, plugged, rusted, busted, leaking component/s all bets are off.

Thinking and wondering, CAMO

 

[Coug]

If cooling system is working correctly, cycling as is should... what would the need for a bypass / over ride switch. Worst case hot or broken it should run.

Hear in the Mojave Desert, highway or trail never worried about over temp condition. I note... any sludge up, plugged, rusted, busted, leaking component/s all bets are off.

Thinking and wondering, CAMO

Some people don't like hearing it go back and forth between fan on and off due to the change in noise level, but other than that I don't see any reason.

 

[Milcommoguy]

Some people don't like hearing it go back and forth between fan on and off due to the change in noise level, but other than that I don't see any reason.

I get what you say and no issues on build it your way. For me... it is the heartbeat of the HumV. If I don't hear it roaring something is UP. On the same DIY mod's, I have a light that comes on when the fan is engaged. (came off of heater. moving the brake lamp to the center was a good idea too. Was always hiding behind the steering wheel. That's it from this peanut vendor.)

Cool ideals to make Humv even cooler, CAMO