I've just finished installing a new alternator in my '03 6.0L Diesel Ex and as I was getting ready to close the hood my son noticed something odd. On the upper right firewall is a plastic blower housing. Attached to firewall right above it is a small flat braided grounding strap that runs down and across the back of the engine and disappears. The strap is melted into the blower housing. As I looked more closely at it, I realized that there was a small diameter light gray wire or tubing that was melted completely through laying right under the grounding strap. Following this tubing out it runs to some sort of valve/sensor on what I'm guessing is a heater hose (steel wrapping around corner of alternator bracket and connecting to rubber hose that runs back to firewall behind alternator). The gray tubing plugs into this valve/sensor. The other end of the gray tubing runs down firewall at far right corner behind blower unit. Can anyone tell me what the tubing is and what I should do about replacing/fixing it? Thanks!

 

I'm 90% sure the little grey tubing (its really small right?), that attaches to big black heater hose assembly thing is a vacuum line. I think you'll just have to replace it.

It is my understanding that the valve thing that the grey tube plugs into is a heater core flow switch or something. Basically (i think), when vacuum is applied, it bypasses the heater core for the A/C, which basically lets the air get colder, instead of running hot coolant through it. If this is the case, the worst thing that will happen without having that little vacuum line plugged in will be A/C thats not quite as cold.

The only thing I would be worried about would be losing vacuum to other circuits (blend door/auto hubs/etc...) if the little grey hose is just sucking in air. I would, if nothing else, plug it up until you can replace it.

Also, Im not sure about this, but my guess is that the other end of that little grey vacuum line is on the back side of the A/C control panel. I say that because it is the blower selector switch which would decide when to apply vacuum to the line, vs when not to.

Hope that helps. Sorry I can't be any more helpful, but im think thats whats happening. Somebody else will come along and say something better, im sure

Isaac

 

It is a vacuum line as afreemanmd said but it is an easy fix. Just cut off the end and go to an auto parts store and buy a short length of rubber vacuum hose and slip it over your gray line to replace only the damaged part. Cut out all the burnt section.

 

I'd search out the other end of that grounding strap . Sounds like a very corroded or poor connection to ground ,hi resistance ,hi heat . Also could be a direct short to ground . ( alternator wireing ?). What caused the alternator to fail ?

 

I would check the grounds on both your batteries .Sounds like when starting it is trying to ground through the strap bacause your battery to Engine/Chassis grounds are dirty or loose.