Standard PVC and rubber insulated cable works fine in ordinary conditions, but it wasn't built for sustained heat, oil exposure or aggressive chemicals. When a cable is running in the wrong environment, the insulation degrades quietly for a while before it fails outright. These are the signs worth acting on early.
1. Insulation that's cracking, discoloring or turning brittle
If the outer jacket near a heat source has gone stiff, yellowed, or started to crack when flexed, the polymer is breaking down. PVC and rubber lose their flexibility well before fluoropolymers like FEP or PTFE even begin to soften - our FEP insulated wires are built to keep their mechanical properties across a much wider temperature band.
2. Repeated nuisance trips or intermittent shorts near heating equipment
Insulation that's thinning or embrittled from heat can arc or short intermittently, especially where wires flex or vibrate. This shows up as a breaker that trips for no clear reason, particularly on lines feeding ovens, furnaces or heating elements. Our FEP insulated heating wires are constructed specifically to hold their insulation resistance under sustained heat.
3. Failures concentrated near engines, exhausts or motor bays
Automotive and off-highway harnesses routed near an engine or exhaust see a mix of heat, vibration and oil that ordinary cable simply isn't rated for. If you're replacing the same harness section repeatedly, it's usually an insulation problem, not a wiring problem - our automotive harness cables are built with tin-plated copper and FEP insulation for exactly this environment.
4. Cable that's swollen, tacky or softened after oil or chemical exposure
PVC absorbs oils and many solvents over time, which shows up as a soft, swollen or sticky jacket. Fluoropolymer insulation - FEP, PFA and PTFE - resists this kind of chemical attack, which is why it's the standard choice in machine shops, process plants and anywhere cable runs near lubricants or cleaning agents. See our full cable catalogue for oil-resistant constructions.
5. The application has certification or compliance requirements standard cable can't meet
If your equipment needs to meet UL, MIL, CE or aerospace wiring standards, general-purpose PVC cable often won't qualify regardless of how it's performing physically. Applications like RTD and thermocouple signal wiring, in particular, need insulation rated for both the temperature and the precision the sensor requires - see our FEP RTD cables and FEP thermocouple extension cable.
What to switch to
The right replacement depends on how hot the environment actually gets and what it's exposed to:
- General heat, oil and moisture exposure: FEP insulated wire covers most industrial and automotive cases at a reasonable cost.
- Higher sustained temperature with tight tolerances: PFA insulated wire or PFA RTD cable.
- The most extreme temperature or chemical exposure: PTFE - see our extruded Teflon wires.
Not sure which one your application needs? Send us the operating temperature, voltage and environment and our team will point you to the right construction rather than have you guess and replace the harness twice.
Frequently Asked Questions
How do I know if my wire insulation is failing from heat?
Look for insulation that has gone stiff, cracked, yellowed or brittle near a heat source, along with nuisance circuit trips or intermittent shorts on the same lines. These are early signs the insulation is breaking down before it fails outright.
What insulation should replace PVC cable near heat, oil or engines?
FEP insulated wire covers most industrial and automotive heat and oil exposure at a reasonable cost. For higher sustained temperatures with tight tolerances, PFA is a better fit, and for the most extreme temperature or chemical exposure, PTFE insulation is the standard choice.
Can I use standard PVC wire for RTD or thermocouple sensor cabling?
Generally no. RTD and thermocouple signal wiring needs insulation rated for both the operating temperature and the dimensional precision the sensor requires, which is why FEP RTD cable and FEP thermocouple extension cable are used instead of general-purpose PVC cable.
