AC Repair in Longmont, Colorado

Longmont sits at 4,984 feet, the lowest elevation in the Boulder County portion of our service area and the mildest altitude penalty we work with anywhere in the metro. The standard derate here is 11.9%, against 12.1% at Erie's 5,026 feet and 12.8% at Lafayette's 5,210. That is a narrow spread, but it is why a Longmont system holds slightly more usable capacity than identical equipment installed a few miles south. Across a city of 92,088, most cooling calls still resolve to a short list of causes. Reach MoJo Home Services at 720-807-4050.

What should I check before calling for AC repair in Longmont?

Four things, all safe and all free. Confirm the thermostat is calling for cool and its batteries are fresh. Check both breakers, the indoor air handler circuit and the outdoor condenser circuit, plus the pull-out disconnect at the outdoor unit. Pull the filter and hold it up to a light. Then look at the condensate drain: a clogged drain line trips a float switch that cuts the cooling call entirely, and the system looks dead while nothing is actually broken. If all four check out, the fault is inside the equipment and worth a technician.

Why does a clogged condensate drain stop a Longmont air conditioner?

Because the safety switch is doing its job. Evaporator coils condense water even in dry Longmont air, that water runs to a drain pan, and biological growth or dust gradually blocks the line. A float switch in the pan opens the low-voltage circuit before the pan overflows onto the furnace or the ceiling below. The result is an air conditioner that will not run and a thermostat showing no obvious fault. Clearing the line and treating the pan restores cooling without anyone opening the refrigerant circuit, and it is one of the more common no-cooling calls we take in Longmont each July.

Does 4,984 feet still count as a high-altitude installation?

Yes. The 11.9% derate at Longmont's elevation applies to gas-fired equipment under the NFPA 54 rule and works as a proxy on the cooling side, where coils move air by volume but transfer heat by mass. It is a smaller penalty than the roughly 15% seen in the far southwest metro, but it is not nothing: a system sized from a sea-level rule of thumb will underperform here. The compensating factor is humidity. Longmont air carries so little moisture that latent load is minimal, so a properly run Manual J often calls for less tonnage than a homeowner expects even after the altitude correction.

What are the most common AC failures we find in Longmont?

In rough order: run capacitors out of tolerance, condensate float switches tripped by blocked drains, dirty filters and evaporator coils choking airflow, contactors with burned contacts, condenser fan motors, and refrigerant leaks. Diagnosis follows a fixed sequence rather than a guess: line voltage, capacitor microfarads against label rating, compressor and fan amp draw against nameplate, temperature split across the coil, total external static pressure, then superheat and subcooling together. Electrical and drain faults are usually settled on the first visit; refrigerant work is the outlier, because the leak has to be located before anything can be repaired, and where it hides sets the length of the job.

When is the right time to schedule AC service in Longmont?

April or May, ahead of the first stretch of 90-degree days. A system that has sat idle since September gives up nothing useful until it runs under load, and the opening hot week of the season is when every no-cooling call in a city of 92,088 arrives at once. A pre-season visit reads the same values a breakdown call would, with enough slack in the schedule to order a part rather than improvise around it. It also catches a drain line before it blocks, which is the single failure most likely to shut a Longmont system down on the afternoon it is needed most.

Who handles permits and sizing for replacement in Longmont?

Component repairs are unpermitted. Equipment replacement falls under Boulder County jurisdiction, the same authority covering Lafayette and Erie, and MoJo files the permit rather than leaving an undocumented changeout in the home's record. On the sizing side, a replacement quote for a Longmont home should show a load calculation run at 4,984 feet, a matched indoor coil, and a line set either reused after verification or replaced. Work in nearby Frederick follows the same sequence.

Other Longmont-area pages

We work AC repair in Frederick, AC repair in Erie, AC repair in Lafayette out of the same dispatch.

If it is the other system acting up instead, start at furnace repair in Longmont.

See AC repair for the service itself, or everything in Longmont for everything we do there.