A2 M1123 - Troubleshooting Stop Lamp Switch

[Coonass77]

I'll revive a year old thread because I'm fighting this on both my M1123 and M1165 at the moment...

When troubleshooting these switches, I've found that leaving the switch installed, disconnecting the linkage rod and and actuating the switch by hand while testing w/ a multimeter can lead to false results. The reason is that when actuating the switch lever by hand, you're typically actuating it inline with the direction of switch travel. Once the linkage rod is installed, it can actually side load the switch lever a little bit which can either make or break continuity on older, worn switches. The switches in both of my trucks test ok when I move the switch by hand, but both start to act flaky and don't give me consistent results when the linkage is connected. Maybe it just happens to be my two trucks, or maybe it's actually a thing. But either way, just something to keep in mind.

 

[Coonass77]

Update on progress...
Two new brake switches ordered and installed. My M1165 is now working exactly as it should. For the M1123, I can't find a "sweet spot" in the adjustment range where both sides of the switch actuate when needed. I can either get the brake lights to work, or the transmission brake signal to work, but not both at the same time. It's like the trip points of the two switches are too far apart to be used by a single actuation lever. Has anyone seen this before? It's a brand new switch from COMTAC. Bad switch? Or does anyone have any secret tips or tricks to get it to work?... Thanks!

 

[aslemmer]

I’m having this issue with a brand new switch. The brake pedal must be damn near to the floor before it engages the brake lights. I’m in the process of doing some other work, so I’m unsure of the transmission switches adjustment as of right now.
The company I purchased the switch from states it is OEM, however the box it came in is definitely not a military box and the label is not military. I’m thinking chinesium, but not 100% as of right now.

Any insight would be greatly appreciated.

 

[papakb]

This is what happens when you try to do more than one thing at a time with mechanical switches built by the lowest bidder. What ever happened to hydraulic switches that activated when they felt pressure? Separate the two functions and let pressure turn on the brake lights and let the mechanical switch control the transmission. That way you only have to adjust the activation point for one switch. I know this might upset the purists out there but it can be done in a way that isn't readily obvious and still allows the functions to happen.

A big part of the problem with these systems is that the incandescent lamps draw a lot of current and cause the switch contacts to arc because only a small section of it is actually making the contact and passing current. Installing LED lights will lessen that draw and keep your switches alive longer.

 

[M371954]

This thread is very helpful, My 2000 M1123 is having similar brake light issues. All other lights work well and without issue. I didn't have any brake lights and I knew I wanted to upgrade to LED TruckLite's all around so I did it. I installed a new new brake switch along with the new LED lights. I understand, I am pushing the ghost (the problem) around by introducing new parts. Now, I still have the same problem, no brake lights. My other lights including the turn signals are working without issue except for hazard lights. The new LED's are functioning the same... no Brake lights.

I am going to try to use the meter and ensure the switch is getting power then look at the turn signal switch as a possible point of failure.

 

[DEA AK]

I've had more Hmmwv's then I can count ..I've had very little issues with the switch.

Hi Retiredwarhorses,
My m1097a2 didn't have a brake switch, I bought one and I see the labeled wires on it (75a, 75b and the wire for the tranny). Looking at the list of wires for the HMMWV that someone posted, all I see are numbers and no diagrams as to where the 75a and 75b connect.

could you provide assistance?

Thank you,
David

 

[peggrw]

Hi Retiredwarhorses,
My m1097a2 didn't have a brake switch, I bought one and I see the labeled wires on it (75a, 75b and the wire for the tranny). Looking at the list of wires for the HMMWV that someone posted, all I see are numbers and no diagrams as to where the 75a and 75b connect.

could you provide assistance?

Thank you,
David

Not sure what info you need. On my clipped diagram from TM-9-2320-280-20-3, 75B labeled in Red and 75A in Green go to Pins K & A respectively on the light switch connector. Other than that I can't be of much help.

 

[DEA AK]

Not sure what info you need. On my clipped diagram from TM-9-2320-280-20-3, View attachment 91342175B labeled in Red and 75A in Green go to Pins K & A respectively on the light switch connector. Other than that I can't be of much help.

Thank you very much!

 

[DEA AK]

Kind of like not planning on being a parent, I didn't plan on having a hmmwv 'right now' but I do. And with it, comes ups and downs... anyway, being up in AK is probably the worst place to have a hmmwv to work on/rebuild/etc.

I saw that the tires have dates stamped on them (i.e. week and year, like "5022" being the 50th week of 2022 or something AND to top it off anything being five years beyond that date is considered 'old.' Then factor in weather cracks or whatnot. What is a guy to do?

I have seen some companies selling tires actually say the tires are old and might have weather cracks. Who can recommend a good company that will tell you what they're selling?

Are the actually new proper size 16.5 inch tires $800 plus each?

Maybe some regular truck tire that isn't super off road knobby tires, I remember the hummers having a GSA tire that was more of a street tire.

Reaching at straws here...

 

[Coug]

Kind of like not planning on being a parent, I didn't plan on having a hmmwv 'right now' but I do. And with it, comes ups and downs... anyway, being up in AK is probably the worst place to have a hmmwv to work on/rebuild/etc.

I saw that the tires have dates stamped on them (i.e. week and year, like "5022" being the 50th week of 2022 or something AND to top it off anything being five years beyond that date is considered 'old.' Then factor in weather cracks or whatnot. What is a guy to do?

I have seen some companies selling tires actually say the tires are old and might have weather cracks. Who can recommend a good company that will tell you what they're selling?

Are the actually new proper size 16.5 inch tires $800 plus each?

Maybe some regular truck tire that isn't super off road knobby tires, I remember the hummers having a GSA tire that was more of a street tire.

Reaching at straws here...

5 years is the cut off for the MT/R tires, due to sidewall failures. For MT or Baja I wouldn't worry as much.

Feltz tire sells tires by date code for very reasonable pricing.

Depending on what tire type you want, 100% tread with guaranteed date codes are in the $275-$350 range.

Freight was pretty reasonable as well. I think when I bought mine a year or two ago a set of 4 2018+100% tread Baja tires were under $1500 delivered to a freight yard about an hour from me. Would have been a couple hundred more for home delivery.

 

[DEA AK]

5 years is the cut off for the MT/R tires, due to sidewall failures. For MT or Baja I wouldn't worry as much.

Feltz tire sells tires by date code for very reasonable pricing.

Depending on what tire type you want, 100% tread with guaranteed date codes are in the $275-$350 range.

Freight was pretty reasonable as well. I think when I bought mine a year or two ago a set of 4 2018+100% tread Baja tires were under $1500 delivered to a freight yard about an hour from me. Would have been a couple hundred more for home delivery.

Thank you for your reply. It sounds like you've kept using your MIL wheels. How are the bolts holding up (that hold the two pieces together?). Do they need replaced often, I am assuming that you always need to replace the wheel gasket and probably have a couple of spares.

Do you know of anyone running after market steel (cheap) wheels with more readily avail 17" tires like the bf Goodrich ones on H2s (for instance). That way Costco or somplace could mount and balance them.

Thank you again

 

[Coug]

Thank you for your reply. It sounds like you've kept using your MIL wheels. How are the bolts holding up (that hold the two pieces together?). Do they need replaced often, I am assuming that you always need to replace the wheel gasket and probably have a couple of spares.

Do you know of anyone running after market steel (cheap) wheels with more readily avail 17" tires like the bf Goodrich ones on H2s (for instance). That way Costco or somplace could mount and balance them.

Thank you again

I've never had to replace any of the studs holding the wheels together. You only need to replace them if something is wrong, like someone over tightened and stretched them, or they have heavy rust damage, or anything like that. As long as you reassemble them with a little bit of caution (don't use your biggest impact gun on it's highest power setting and hammer away at them) they should last many cycles.

I've probably done about 20 wheels taken apart and back together since I bought my truck, and only had to replace the o-rings on a couple of them, and those usually when I first get them. Several have been apart 3+ times and no issues.
I tend to fill up the tire, then let it sit for a day or two and check pressure again before installing them back on the truck.

 

[Mogman]

I've never had to replace any of the studs holding the wheels together. You only need to replace them if something is wrong, like someone over tightened and stretched them, or they have heavy rust damage, or anything like that. As long as you reassemble them with a little bit of caution (don't use your biggest impact gun on it's highest power setting and hammer away at them) they should last many cycles.

I've probably done about 20 wheels taken apart and back together since I bought my truck, and only had to replace the o-rings on a couple of them, and those usually when I first get them. Several have been apart 3+ times and no issues.
I tend to fill up the tire, then let it sit for a day or two and check pressure again before installing them back on the truck.

Just like your wheel lug nuts these should ALWAYS be torqued with a good torque wrench to specifications.
Initial 85ftlb then 125ftlb

 

[DEA AK]

I've never had to replace any of the studs holding the wheels together. You only need to replace them if something is wrong, like someone over tightened and stretched them, or they have heavy rust damage, or anything like that. As long as you reassemble them with a little bit of caution (don't use your biggest impact gun on it's highest power setting and hammer away at them) they should last many cycles.

I've probably done about 20 wheels taken apart and back together since I bought my truck, and only had to replace the o-rings on a couple of them, and those usually when I first get them. Several have been apart 3+ times and no issues.
I tend to fill up the tire, then let it sit for a day or two and check pressure again before installing them back on the truck.

Great, thank you, I appreciate your help.

 

[DEA AK]

Just like your wheel lug nuts these should ALWAYS be torqued with a good torque wrench to specifications.
Initial 85ftlb then 125ftlb

I am assuming the military treated this truck like their own personal vehicle, doing proper service to spec... hahaha right!

Thanks for your help, I appreciate it.