The Stovebolt Site Forums The Shop Area The Electrical Bay Is "crosslinked" wire (i.e. SXL) necessary?

When using plastic covered wire is it necessary to use the crosslinked polyethylene (GXL,SXL,TXL) in the engine compartment like the wire manufacturers recommend, or will the PVC covered wire like is readily available at most parts stores do for a truck that isn't going to be driven that much? It's no doubt stepping things up a notch to use the XL wire, but I'm guessing most folks just use the PVC for whatever they need to repair on a vehicle and don't have any trouble. I don't think I have ever used the XL and I can't recall anything I have repaired in the engine compartment failing.

I'm using it to "repair" one of the replacement wiring harnesses I got from Jim Carter, which was for the birds (wires missing, etc.). I can't imagine them using the high dollar wire to make these with because the plastic covered terminals on them look like the cheapest thing they could find. The thing that concerns me is the length of wires running right next to the exhaust manifold along the inner fender on these old trucks (1941).

On the other hand one can't just go down to Autozone and buy crosslinked wire. You have to order it, and usually in quantity, so I want to know it's necessary before I delve into this endeavor. My personal feeling is it isn't because even if the heat of the exhaust manifold did degrade the PVC wire insulation it would take a very long time for it to degrade it enough to matter on a "hobby" truck.

no it's not 'necessary', the original stuff was cloth covered, then a little later, cheap pvc .... both have lasted the 40-50-60 years these vehicles have been in service without melting even laying on the engine .... just make sure any wiring you do is properly routed and secure so it doesn't flop around

"Cross-linked polyethylene" is otherwise called PEX, as in the plumbing tubing, if you're wanting your wiring to last 100 years, go to a plumbing store and buy some PEX tubing to use as 'conduit'

Bill

No, crosslinked (XL) automotive wire is a much higher quality of wire than PVC plastic insulated primary wire that is commonly found at parts stores. It's insulation can withstand much higher temperatures. It is explained here: http://www.automotivewire.info/automotiveprimarywire.htm .

This illustrates why parts stores probably don't carry it: the average person who works on cars doesn't know the difference so stores figure they would never sell any of it because people would just buy the cheaper PVC insulated wire.

as I said, it's PEX, high density polyethylene, a different type of "primary wire" .... and it's not generally found in any parts or electrical/electronics store because it's overkill, not because suppliers 'think you don't know better' .... current OEM involves computers and all the latest and greatest including using the XL plastic for the ducting but that doesn't make it "higher quality", spend the money if you wish, but no truck we deal with here came with it and as I said for your query, it is not "necessary" providing your routing the wiring properly, as original

Bill

I think the PVC insulated wire's insulation will eventually fail because it can't withstand near the temperatures of a boxed in engine compartment of one of these old trucks. I can't prove this, however, so I just use common sense: PVC is only good to 185 degrees Fahrenheit and engine compartments can get over 300 degrees. I think it's just a matter of how fast this will occur in a truck that isn't driven that much. It might take decades or just a few years for the PVC insulation to deteriorate to a point where problems occur in a truck that is hardly ever driven, I don't know. That's why I posed the question.

If I was building a wiring harness for something that mattered that was driven daily I wouldn't skimp on the wire. Volvo skimped on the wire on the 240's they built and they ended up with a bunch of cars that had to have their wiring harnesses replaced or repaired. Anyone that's ever owned one of these cars (like me) will tell you old 240's had crappy wires.

Looks like PEX wire is only used in the construction industry for building and overhead wires: http://en.wikipedia.org/wiki/Cross-linked_polyethylene#Other_uses_for_PEX . I can't find any such thing as PEX wire used for vehicle wiring, just the cross-linked wire types I mentioned earlier. Google it up.

well, the answer is it will take decades, there are plenty of high mileage old vehicles around with perfectly good original pvc wiring, I have some of them .... as I said, it's your money, if you think you need the most expensive materials, go for it, or use some PEX tubing for conduit for the same protection you think is needed

there is no such thing as "PEX wire", PEX [polyethylene, cross linked] or XLPE [cross-linked polyethylene] is the plastic, that's why they call it XL wire - and yes, as stated in that article, cross-linked polyethylene has been used for quite awhile as the insulation of choice for high voltage applications, I suspect you'd find it's on most modern battery and welding cables

Bill

The "medium voltage" referred to in the Wikipedia article is also referred to as the 15kv class.

That's 15,000 volts. The PVC is MORE than adequate for any of our trucks.

The rolls of primary wire I have gotten from NAPA say "meets or exceeds oem factory standards" on the box. That's good enough for me.

Les

As Bill says, pvc is adequate. The wires have a safety factor built into the heat spec. 300 deg under the hood? I'm not sure that is correct. Recent studies using thermocouples show engine compartment "center of hood" temps at below 100 deg. High temps were recorded at thermocouples mounted on catalytic converter and exhaust manifold (direct contact.) Lots and lots of pvc wires under hoods of old trucks across America, Canada and beyond, no melting yet. No wire will withstand direct contact with an exhaust manifold or pipes... or a catalytic converter which I'm sure we all have.? Not.