A Fleet Air Compressor Purchase: What I Learned Ordering Viair for 12 Trucks

The Request That Started It All

The request came in on a Tuesday afternoon in late February 2025. One of our field supervisors leaned into my office and said, sort of apologetically: "We need air compressors in all the company trucks. Can you make that happen?"

For context, I'm the office administrator for a 28-person civil construction company. I handle purchasing for everything that isn't raw material: tools, PPE, shop supplies, and the occasional office chair. I'm not a mechanic. I'm not an electrician. But after about five years of ordering equipment for this company, I've learned how to read a spec sheet and when to ask for help. I took over fleet purchasing in 2024, and I'm the one who lives with the consequences when a part doesn't work.

Why I Started With a Portable Unit

We had a handful of cheap portables floating around the shop. They were the kind with a cigarette-lighter plug and a coil hose. They worked okay for topping off a tire in a warm garage. They weren't okay on a job site in January. One burnt out in 2023 while a guy was trying to air up a grader tire after a blowout. The replacement cost more than the compressor, and the lost time was worse. Saving $40 on a no-brand compressor ended up costing us a morning and a tire.

So I decided we needed something reliable. I ordered a Viair 88P air compressor from our local distributor before committing to a fleet-wide rollout. (Note to self: always test one unit before ordering ten.) The Viair 88P air compressor did what we needed in the shop. It has a 33% duty cycle at its max pressure of 72 PSI, which is enough for filling truck tires and trailer tires if you let it rest between cycles. It was small enough to toss in a truck, and it didn't feel like a toy.

The Onboard Air Decision

The 88P was a good portable, but it wasn't the right solution for trucks that run eight hours a day. The supervisor wanted onboard air: a compressor mounted under the hood or on the frame, wired to the battery, with a switch in the cab. That's when I had to learn more about wiring than I ever expected.

Our shop foreman said, "Order the Viair 80 amp relay kit. You don't want the compressor running direct through a toggle switch." I asked why. He explained that a relay lets a small switch control a big circuit. The compressor can draw 30 amps or more, and you don't want that current going through a cheap switch in the cab. The Viair 80 amp relay kit came with a harness, an inline fuse, and terminals that matched the compressor. I ordered eleven of them.

The Car Audio Control Line Question

Then came a question I did not expect. One of our younger techs asked whether we could use a car audio power amplifier control line as the trigger wire for the relay. He had installed stereos in high school and still had a spool of blue remote wire. The idea made sense in a way: if that wire can tell an amplifier to turn on, why can't it tell a relay to close?

I didn't want to dismiss him. I called a mobile-electronics installer we've used on a few vehicles. His answer was blunt: "A car audio power amplifier control line is a signal wire. It's meant to wake up an amp, not to feed a relay that controls an air compressor. Could it work? Probably. But is it the right way? No." We used the relay kit as intended. I can't tell you exactly how many amps a relay coil draws or what gauge wire you need for every install. What I can tell you is that the guys who install radios for a living don't want to use that wire for this.

A Side Quest: Bike Racks and CB Radio Interference

While the compressor order was being routed, I got pulled into two unrelated requests. First, our HR person wanted a 4-bike Thule rack hitch for a crew-cab truck. Second, one of our drivers asked a question that made me laugh at first: "Can CB radio interfere with WiFi?"

I'll tackle the bike rack first. We ordered the Thule 4-bike hitch rack for the 2-inch receiver on the truck. The fitment notes said it needed enough clearance for the hitch angle on our trucks, so we checked the receiver rating and the rack weight before ordering. No one wanted to find out on a Saturday morning that the rack drags on an incline. That turned out fine.

Now, the CB question. On paper, CB radios operate around 27 MHz and Wi-Fi operates at 2.4 GHz or 5 GHz. They're far apart. But our driver's iPad kept losing its Wi-Fi connection when he keyed the mic. The radio shop we use found the source: a cheap 12V USB adapter in the same power outlet. The adapter was generating broadband noise, and the CB wasn't the real culprit. We swapped the adapter and the interference disappeared. I'm not saying that's the answer for every truck. I've only worked with CB installations in our fleet—about six vehicles. If you're on a boat or a heavy truck, your experience might differ.

What I Learned From All This

The first lesson is boring but real: buy the right tool once. We could have bought ten more Viair 88P air compressors and handed one to each crew. The 88P is a great portable unit, but this project needed onboard air. The relay kit was a small part of the total cost, but skipping it would have made everything else unreliable. (Mental note: ask for a wiring diagram before ordering the next batch.)

Second, expertise has boundaries. I'd rather work with a specialist who says "I don't do that" than a generalist who says "sure, I can handle it." The mobile-electronics installer said he didn't touch CB antennas. But he told us what not to do with the relay. That honesty earned our trust for the next project.

Third, verify before you trust a product recommendation. I read the installation sheet for the Viair relay, looked at the wiring diagram, and checked the amp rating. I don't understand every detail, but I know enough to notice when something doesn't add up.

My experience here is based on one fleet and about 12 vehicles, all Ford and Ram pickups. If you're fitting out RVs, heavy trucks, or a different compressor brand, your setup will probably be different. I can't speak to every edge case. I'm the person in the office who orders the parts and makes sure they arrive, not the one under the hood.