# AC System Leak Detection in Upland > Find the AC leak before you pay for a recharge. Route 66 Auto Repair in Upland uses UV dye, electronic detectors and standing tests. Source: https://route66autorepairshop.com/cooling-heating-ac-services/ac-system-leak-detection Updated: 2026-09-17 Business: Route 66 Auto Repair, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699 Hours: Monday to Friday 8 AM–5 PM, Saturday 8 AM–2 PM, Sunday closed **TLDR:** We combine **UV dye**, an **electronic detector** and a **standing test** so the leak is located, photographed when possible, and quoted before any recharge. Route 66 Auto Repair in Upland finds AC leaks before we refill a system, because a recharge without a repair just rents you cold air. We use several methods, since no single one catches every leak: UV dye, an electronic refrigerant detector, and a vacuum or nitrogen standing test. You get the location, a photo when we can take one, and a written estimate to fix it. ## Which leak detection methods do we use? ### UV dye A small amount of fluorescent dye circulates with the oil. Under a UV lamp, a leak glows yellow-green. It is excellent for slow leaks at fittings and crimps, but it needs time to work its way out, so we may add dye and ask you to drive for a few days. ### Electronic detector A handheld sensor sniffs for refrigerant vapor. We move it slowly beneath each component, since the vapor sinks. It finds leaks in places dye cannot be seen, like inside the evaporator case. ### Standing vacuum or nitrogen test With the system empty, we pull a vacuum and watch whether it holds, or fill it with dry nitrogen and watch the gauge. A drop confirms a leak even when it is too small to find right away, and nitrogen is safe to release. ## Where do car AC systems usually leak? - The condenser face, from rock strikes - Crimped ends of rubber hoses - Service port valve cores and missing caps - O-rings at line connections - The compressor front shaft seal and body seams - The evaporator, inside the dash ## Our leak detection process 1. **Check for existing dye:** We look for dye from past service before adding more. 2. **Sniff the system:** The electronic detector checks each component, fitting and the evaporator drain. 3. **Run a standing test:** A vacuum or nitrogen hold confirms whether the system is sealed. 4. **Report the location:** You get the leak location, a photo when possible, and a repair estimate. ## What's included in AC leak detection - Visual inspection of lines, fittings and condenser - UV lamp check for dye - Electronic detector sweep - Vacuum or nitrogen standing test - Leak location notes and photos - Written repair estimate ## How pricing and timing work Most leaks are found in one visit. A very slow leak may need dye and a return trip, and we explain that choice up front. The diagnostic fee is stated at the counter and applies to approved related repair. Once the leak is fixed, the [AC system recharge](https://route66autorepairshop.com/cooling-heating-ac-services/ac-system-recharge) follows. If the leak is at a hose, see [AC hose replacement](https://route66autorepairshop.com/cooling-heating-ac-services/ac-hose-replacement). For line damage, see [AC line repair](https://route66autorepairshop.com/cooling-heating-ac-services/ac-line-repair). ## Frequently asked questions ### Why find the leak before an AC recharge? Refrigerant does not get used up. If the system is low, it leaked, and a recharge alone will leak out again. Finding the leak first means you pay for one fix instead of repeated refills. ### Can you find a leak if my system is completely empty? Yes. We use a standing vacuum or nitrogen test, which does not need refrigerant, and can add a small charge with dye to trace the leak afterward. ### What if you cannot find the leak? Some leaks only open when parts are hot or under vibration. We add dye, charge the system, and ask you to return after some driving so the leak shows itself. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.