There are definitely floating grounds. Car audio systems have used floating grounds for 30+ years. I wouldn't be surprised if there are floating grounds in the computers. Chrysler has used switched grounds for a while, too.

 

So your suggesting that possibly my installer didn't know what he was doing when dealing with Rams?

My understanding what he was seeing was that the ground was not always a 0.. it varied, I don't know by what magnitude or direction however. It sure caused weird issues though.. intermittent issues with the starter and such... it would work for a while, then sxxxt the bed the next time I tried..

 

You can follow the grounds off of the battery. One goes to the frame and one goes to the starter. I also spotted a thin braided one near the fire wall on my truck when I had the passenger wheel well liner removed. In my case it was broken in half...did not fix it yet.

If you are concerned you can disconnect the battery cable completely and clean all off the connections with some emery cloth.

Steve

 

Thats what I got back from him... How do you test for a floating ground?
+ Known 0 (ie Battery post)
- Suspected floating ground?

 

Check for voltage between your -terminal and frame with the engine running and not running. A floating ground means your ground (frame) isn't tied into your power source (battery). I do not think it's likely, I'd say he was having a problem with one particular component having a floating ground, not the entire truck.
Steve

 

It is highly unlikely. I haven't seen a "Floating Ground" in any cars except for some very early 1950 and earlier vehicles that have very simple electronics and the radios mount (and ground) to the radio bracket by one single bolt.

I have never ever seen a "floating ground" on any vehicle with a computer.

A Floating ground literally means that there is NO PHYSICAL GROUND CONNECTION.... and the ground on our vehicles is the chassis, which is also connected to the Negative Terminal on the Battery.

So it is possible that what he is seeing is a "Ground Loop" but no way in hell is he seeing a "floating ground".

Now a little theoretical-history on a Floating Ground... they were used in VERY VERY high voltage transformers, and when there was a problem with the transformer the thought was that instead of "vaporizing" the ground rod and wiring, causing a very unsafe connection to the output wires, they basically put a rod "nearby" and a rod coming off of the transformer (I'm wayyyyy oversimplifying this which is why I'm sure people will rebut what I'm saying) and they would use a "floating ground" so when something when wrong there would be this CRAZY Arc going to the ground which is dangerous, but was the only thing they could do at the time in an attempt to minimize power outage to as many customers as possible. (again I'm oversimplifying)

Now I'm not going to get into Capacitance and "Phase-to-Phase" topics because that will take a considerable amount of time that I'm not willing to take unless you're paying me, besides there are a million textbooks on that stuff.

What they found was that when this "arc to ground" occurred it would almost always "fry" the transformer, so it would require complete replacement 99% of the time. Which is why they now use other methods of "grounding" now in combination with "floating grounds", which are safer for people and equipment. (This is kinda sorta how "Neutral Grounding" was invented/discovered)

A big plus to this "floating ground" aka "ungrounded connection" was that it greatly reduced AM/FM Radio Interference, and power would not be "interrupted" it would simply keep going until the fault was fixed or the source is cut. (which is why old car radios were grounded like this or not grounded at all in some cases)

Now keep in mind I am really only talking about AC connections right now, and that is because it is extremely hard to get DC to behave correctly with a "true" floating ground" as it will just take the path of least resistance which is usually an attempt to go "back the way it came" which is why Diodes are needed so frequently in DC systems.

I'm going to stop here and simply post a link to a video that will kind of illustrate what I am talking about at the 101 level.


Anyways, good luck in the goose hunt for the floating ground.

I personally think the OP is experiencing a "ground loop" or possibly a very serious short circuit somewhere. And those are very very difficult to trace in a DC system...

I haven't seen the truck first hand so its hard to identify without a doubt what the problem really is.

 

I live in Florida and own a 2007 Dodge Nitro and the AC compressor quit rightat the beginning of the summer. (Murphy’s Law, right?) The Dodge Nitro at thetime had about 90,000 miles so I was not too surprised and I took it into the autoshop that I have used for 25 years. They replaced the compressor with one fromthe manufacture which included a one year guarantee. Perfect!

Well it worked fine through the rest of the summer, however the beginning ofthe next summer the AC compressor quit again!? So I took back to the same shopand they promptly replaced this unit for free and I’m on my way. (I am now oncompressor number two) but I was very happy that I went to a reliable shop ANDthat I purchased the replacement compressor from the Manufacturer and not somecheaper after-market unit. Feeling pretty smart!

Well, this scenario repeated itself again this summer, still within this secondunit’s one year warranty. So I make an appointment at the same auto shop who diagnoseda leaking compressor (again). The shop contacted the manufacturer to replaceit. But this time the manufacturer is refusing to replace the compressor again,saying there must be something wrong with my Dodge Nitro!? Hello? It’s your (DodgeBrothers) vehicle…. I should have mentioned that both failures are apparentlydue to a leak where the unit is pressed together? The shop states that it isnot leaking from any of the fittings or from improper mounting, alignment, etc.I asked that specific question.

Has ANYONE had a similar situation? I don’t understand how the Manufacturer canjust decide NOT to warrant the unit? IF it were out of warranty I wouldunderstand, but it isn’t. Both times Dodges’ compressor FAILED and I’m withoutAC. BTW I commute 70 miles each day to work, here in the sunshine state. This isnot a good situation and I’m STEAMED!

 

I live in Florida and own a 2007 Dodge Nitro and the AC compressor quit rightat the beginning of the summer. (Murphy’s Law, right?) The Dodge Nitro at thetime had about 90,000 miles so I was not too surprised and I took it into the autoshop that I have used for 25 years. They replaced the compressor with one fromthe manufacture which included a one year guarantee. Perfect!

Well it worked fine through the rest of the summer, however the beginning ofthe next summer the AC compressor quit again!? So I took back to the same shopand they promptly replaced this unit for free and I’m on my way. (I am now oncompressor number two) but I was very happy that I went to a reliable shop ANDthat I purchased the replacement compressor from the Manufacturer and not somecheaper after-market unit. Feeling pretty smart!

Well, this scenario repeated itself again this summer, still within this secondunit’s one year warranty. So I make an appointment at the same auto shop who diagnoseda leaking compressor (again). The shop contacted the manufacturer to replaceit. But this time the manufacturer is refusing to replace the compressor again,saying there must be something wrong with my Dodge Nitro!? Hello? It’s your (DodgeBrothers) vehicle…. I should have mentioned that both failures are apparentlydue to a leak where the unit is pressed together? The shop states that it isnot leaking from any of the fittings or from improper mounting, alignment, etc.I asked that specific question.

Has ANYONE had a similar situation? I don’t understand how the Manufacturer canjust decide NOT to warrant the unit? IF it were out of warranty I wouldunderstand, but it isn’t. Both times Dodges’ compressor FAILED and I’m withoutAC. BTW I commute 70 miles each day to work, here in the sunshine state. This isnot a good situation and I’m STEAMED!