Rodents Are Chewing Bay Area Car Wiring. Here's What to Do
Soy-based wiring insulation attracts rodents, and South Bay cars that sit a few days are the usual target. The early signs cost nothing to fix; the late ones don't.
If your car has an electrical fault that comes and goes, and it spends nights parked outside or in a garage near landscaping, open the hood and look at the wiring before you pay anyone to chase the fault electronically. Rodent damage is common here, and unlike most intermittent electrical problems, it's visible.
Why cars specifically
To meet environmental targets, many manufacturers moved from petroleum-based wire insulation to soy-based coatings from roughly 2010 onward. It biodegrades better at end of life. It is also, to a rodent, food.
Add a warm engine bay after a commute, soft sound-deadening to shred for nesting, and a cabin filter housing that's dry and enclosed, and you have close to ideal shelter. Cars driven daily get hit less because the disturbance is constant. The ones that get hit are the second car, the weekend car, and anything left for a week while you're traveling.
The signs, cheapest first
- Droppings on the engine cover or in the airbox. The earliest sign, and the point at which this costs essentially nothing to solve.
- A smell from the vents when the fan first comes on — usually nesting material in the cabin air filter housing.
- Shredded insulation or nesting debris around the battery tray, under the airbox, or sitting on top of the transmission.
- An intermittent warning light with no pattern to it — often a partially chewed wire making and breaking contact as the engine moves on its mounts.
- A no-start with a healthy battery. By this stage something has been severed outright.
Where they get in, and what a real repair involves
The common entry points are the gap behind the wheel arch liners, the cabin air intake at the base of the windshield, and any gap left where a previous repair didn't reseat a shield. Rodents don't need much: if a pen fits, they fit.
Repair depends entirely on where the damage is. A chewed section on an accessible loom can be cut back, spliced properly with heat-shrink and soldered joints, and re-wrapped in an hour. The same damage inside a harness that runs behind the engine or under the intake manifold is a different job, because most of the labour is getting to it rather than fixing it.
Be wary of a repair that's just electrical tape over the damage. Tape traps moisture against a splice and the fault returns, usually in the rain, usually somewhere inconvenient.
If you suspect it right now
Don't start the engine yet. If a wire is chewed through and touching something it shouldn't, cranking it can turn a splice repair into a blown module. Open the hood in daylight and look at the top of the engine, around the airbox, and along any loom you can see.
Take photographs before you touch anything — for the insurer, and so we can see what it looked like undisturbed. Then check the cabin air filter, which is usually behind the glovebox and is where nesting material collects first.
If you find droppings but no visible damage, you've almost certainly caught it in time. If you find bare copper, have it looked at before you drive it any distance.
What actually deters them
Peppermint oil and ultrasonic gadgets get recommended constantly and the results are inconsistent at best. What reliably helps is duller and more practical: remove the food and the shelter.
Don't store birdseed, pet food or compost in the same garage as the car. Keep landscaping and woodpiles cut back from where you park. If the car sits for long stretches, park it somewhere with light and foot traffic rather than a quiet back corner, and open the hood every week or two to check.
Rodent-deterrent tape — a capsaicin-treated electrical tape sold by several manufacturers — is worth wrapping around exposed harness sections if you've been hit once. Being hit once is a reasonable predictor of being hit again, because the conditions that attracted them usually haven't changed.
Insurance
This surprises people: rodent damage is generally handled under comprehensive coverage rather than collision, because it's classed alongside other non-collision damage. Whether it's worth claiming depends on your deductible against the repair cost, but it's worth asking before you assume the whole bill is yours.
Take photographs of the droppings and the damage before anything is cleaned up. Adjusters ask, and a cleaned engine bay makes the claim harder to evidence.
Bring it in and we'll tell you which stage you're at. Often the honest answer is that you caught it early and it's a clean-up, not a repair.