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Incorrect, you'll get 24v at the motor and that is only if that compressor motor is case grounded. Many of the good ones are not. The only sparks that could fly is the result of doubling the voltage that the motor is designed to operate at.

No, Undysworld is correct: if the compressor negative terminal is also the compressor chassis, and if the chassis is connected to the truck chassis, then the lower battery (the one that has it's negative connected the the truck chassis) will be shorted; certain to fry the negative compressor wire and make the sparks fly!

If everything we did to our trucks had to be UL safety approved we would never have anything but 24V equipment. There are ways of using 12V parts, but this quickly becomes frought with ways to "let the smoke out of things". Do so at your own risk.

Jim M.

First, thank you everyone for your replies to my original post. I wish I were nearly as electrically savvy as many of you clearly are. While I THINK I understand what needs to be done to use one of Viair's portable 12v compressors with our trucks, I'm now sufficiently hesitant to simply get a 24v system and make it an OBA system, and sacrifice the convenience of the portable system.

Jimm391730 wrote: No, Undysworld is correct: if the compressor negative terminal is also the compressor chassis, and if the chassis is connected to the truck chassis, then the lower battery (the one that has it's negative connected the the truck chassis) will be shorted; certain to fry the negative compressor wire and make the sparks fly!

100% incorrect and a lot of "if" statements.

We are getting lazy on the "quote" button. Read complete statements .

What has been said is if a 12v device is connected to the "upper" battery, and the chassis of the device ( assuming it's housing is grounded) comes in contact with the vehicle chassis, you will have 24v going to it, and you have smoke released.
Plain and simple.

SO, if you just HAVE to run something on 12v, use the lower battery, and realize you're going to be replacing batteries sooner than later.

David Dunn wrote:What has been said is if a 12v device is connected to the "upper" battery, and the chassis of the device ( assuming it's housing is grounded) comes in contact with the vehicle chassis, you will have 24v going to it, and you have smoke released.
Plain and simple.

Furthermore, this entire topic is about a Viair compressor. One that is NOT case common. The entire argument is moot and off-topic.

delete

undysworld wrote:Fleq,

The relevance of this discussion seemed to be with regard to operating a 12v compressor (of unknown ground) on the Pinzgauer, using one 12v battery. The topic WAS

Using 12v Viair Compressor with 24v Pinz

.

EXACTLY, the topic of this thread is using a 12V VIAIR compressor on a 24V system. A Viair compressor DOES NOT have a ground that is case common. That is a FACT and is KNOWN. Everything else that the "what if" crowd is introducing is confusing the issue and of no help to THIS topic.

Sorry to have troubled you.

Fleg wrote: Furthermore, this entire topic is about a Viair compressor. One that is NOT case common. The entire argument is moot and off-topic.

I talked to Viair this morning and tech support said that the case weren't isolated and the possiblity of a case grounding was there, if the housing came in contact with the vehicle chassis and the leads were to the upper battery, it would get 24v.

As much as you want to call it moot and off topic, this is relevant to the safety aspect of use of the Viair or any 12v electrical item in a 24v system.

Fleg,

It appears my suggestions were accurate, on-topic or not. I didn't post them on here for my own help. What seemed common sense to me might be of some help to others, but only if I offer it up. Obviously, some, including yourself, know little about 24v auto electrics. I myself make no claims of genius, but I know a little. Why that pi$$ed you off, I don't know.

If I somehow offended your purist sensibilities by going off topic, I apologize, but as Dave observed, it is relevant to the use of many (if not most) 12v devices.

Furthermore, IIRC, I agreed with you that for many folks a 24v compressor was a wise choice.

Call me the "what if" crowd, whatever. If you don't wish the benefit of others with more knowledge than yourself, that's your issue. But please don't come around here badmouthing people (myself included) to the point where they no longer feel it worthwhile to post information.

Paul

Well said, Paul. And no offense intended to Fleg or anybody else, but EVERYTHING commented upon here, from the good through the "ifs" to the bad are generally good food for thought for everyone, even if those thoughts are rejected out of hand.

The "if" statements that I pose are specifically to keeep me from opening my mouth to change feet. I know that I am not likely to be 100% correct without knowing every detail, and I never claimed to.

In the end, it appears that we have all be convincing enough to Hersir to get him to go with a 24V compressor for all the reasons stated. And perhaps this helps shed some light on using other 12V accesories too.

Take all with a grain of salt and good spirits.

Jim M.

Wow I missed alot. Not everything is available in 24vdc IE. fuel pump. Biggest negative I have seen about tapping one battery is in the charging as the one that is tapped never gets fully charged as I think Jimm mentioned. I have been stranded in the past from one poorly charged battery and some ghost drains.

Prefferably a well aged(good spirited) Irish Whiskey

Jim M.

Thank you, and Amen.

Jim L.

Well, if it's to be Irish whiskey, I'll suggest the Midleton (or Bushmills Distillery Reserve if you're in Antrim).

But for meself, it's Aberlour a'bunadh tonight.

Cheers to all!

David Dunn wrote:

Fleg wrote: Furthermore, this entire topic is about a Viair compressor. One that is NOT case common. The entire argument is moot and off-topic.

I talked to Viair this morning and tech support said that the case weren't isolated and the possiblity of a case grounding was there, if the housing came in contact with the vehicle chassis and the leads were to the upper battery, it would get 24v.

As much as you want to call it moot and off topic, this is relevant to the safety aspect of use of the Viair or any 12v electrical item in a 24v system.

Rather then believe what someone posts on a internet forum, I actually took my Fluke DMM to my Viair and confirmed, it is case isolated. Might want to check your source again.