electric trouble

[N1265]

Hi guys,

I am having some electric trouble with my M880..... The alt gage vibrates back and forth and increases when I turn on the lights. the lights flicker constantly.

the truck idles fine and everything works and there are no blown fuses.


Any ideas on what this could be?

thanks : Nick

 

[TheSHAD0W]

Sounds like a bad connection to the battery. Check your connections, and you might need to replace wires.

 

[N1265]

I checked the cables to the battery and they seem fine. I also checked the power feed comming off the alt. and the ground wire going to the fender..... the problem continues

I noticed tonight that when I turn on the ingnition and or light switch on I get a loud "click" noise comming from under the dash.


any idea what this noise is and if it is my problem?

Thanks : Nick

 

[Larry_R]

The light flickering might be the alternator or the voltage regulator. If the voltage regulator isn't getting a good ground it does some wacky things. Have you taken it to the local auto parts store and had them check it while it's running? Might find something out.

As far as the "clicking" noise your getting. Mine has always had a similar sound when I turn on the headlights. It's coming from a relay or breaker under the dash. I think it's all part of the Military wiring that is put on them. It's a normal sound. I have three M880 series trucks, my partner has three, and my wifes cousin has one. They all do it. It's never affected anything so I don't worry about it.

When you find out what the prob is lets us know. All the shared info is a good thing.

 

[N1265]

Thanks for the advice ....

I have talked with an educated mechanic... he also recommends checking the alt. any ground wire and voltage regulator. I will do this when the truck is closer to getting on the road.

But for now I am trying to handle a problem with my tranny fluid. It looks like it has become contaminated with water. ( milky apperance) Is there any way of draining the tork converter and coolant lines? other than just changing the fluid 2 or 3 times ?

also, can anybody tell me the right tranny fluid to use in the M880s.

thanks again : Nick

 

[N1265]

Well,

I just got the beast on the road and took it in and had the alt. and voltage reg. tested..... They tested ok,

I am still have the jumping alt. gage and now I just noticed that when I but on the breaks the front turn signals come on ( very dim)

any ideas?

Thanks Nick

 

[clinto]

Somehow, the system is feeding voltage up throught the brake light circuit(s) into the front lamp harness wiring.

My 383 4 speed Road Runner would upon application of the brakes, start making the underdash reverse light glow. It ended up being a taillight grounding issue.

 

[N1265]

Ok, I will look there first,

Thanks Nick

 

[Larry_R]

Nick,

Check the wire connections on the back of the alternator gauge. The alt gauges are notorius for melting down and jumping around if the connections aren't tight. But it sounds like a ground problem.

If you have a volt meter, take some readings at the battery and at the back of the alt with the truck running. See if you are still getting the flucuation on your meter. It's gonna be a process of elimination. Let us know what you find out!! Larry....

 

[N1265]

The conections at the alt. look fine, they are not burnt or coroded. and everything there is tight .

I do not have a volt meter but the guy who checked the system said he also seen a dip in the system but it checked out good. he used a device that clamped on to the pos. and neg. side of the battery ...flipped a couple of switches and read the needle at an idle and at a slight rev.

does this info tell you guys anything?

thanks Nick

 

[cranetruck]

Grounding several lamps or devices to the same point, like a fender or piece of sheetmetal that is not itself grounded correctly will turn on the other lamps (or devices) at a lower intensity as the ground path is rerouted through it.
When your MV was first put together ALL metal parts were joined, using external/internal tooth washers and/or grounding straps to eliminate this problem and also to improve radio transmission/reception. In time the bonds may have come loose or pieces put back together without the correct washers.

Bottom line: Check all grounds, make sure the fender parts are grounded to the frame etc.
You can use a DVM (Ohm scale) for a fairly good measurement, but turn off power when using it.
Or use the Volts scale, connecting/holding the black probe to battery ground terminal (not the clamp) and the red probe to the light bulb that is supposed to get the full 24 volts. If it is less, then you have a poor return path.

Bjorn

 

[N1265]

thanks for the advice, Looks like I got a lot or work ahead of me.

Thanks, Nick

 

[N1265]

looks like there has been some " creative wiring " done to the truck,

the orginal wiring does not carry a break signal to the tail lights...and someone ran a wire to the break switch and tapped it in to the brown wires which are for the running lights. ( this is why when I apply the breaks the front turn signals light up)

However I am having a hard time figuring out how to go about solving this problem and getting it wired correctly.


I need to know :

1) if I simply unplug the blackout switch will it disconnect the blackout system so I can eliminate it being the problem when I am trying to diagnose this situiation. Or does everything run threw this switch ?

2) under the dash behind the ashtray is a blue plastic box with 4 wires going to it.... black,green,white,orange does this box have anything to do with the lighting? if so what is it called and do they normally go bad?

thanks Nick

 

[cranetruck]

Correction on the Oct 10 post.
This is what I said:

Or use the Volts scale, connecting/holding the black probe to battery ground terminal (not the clamp) and the red probe to the light bulb that is supposed to get the full 24 volts. If it is less, then you have a poor return path.

Should read:

Or use the Volts scale, connecting/holding the black probe to battery ground terminal (not the clamp) and the red probe to the light bulb return terminal. If the voltage is more than a fraction of a volt, then you have a poor return path.

Sorry about that.
Bjorn

 

[N1265]

Hi guys,

well I finally got around to dig into my lite problem tonight.....

It seems that all the power for the break lites run threw the turn signal switch. after tracking everything down and isiolating the problem there, I tore the cam for the switch apart and found the problem. ( A semi melted contact )


Thanks for all of your suggestions, you helped me to save me a ton of money.

Thanks again : Nick