Fluke 116 vs Fluke 115 for HVAC Troubleshooting

Specs side by side

Specs checked against manufacturer documentation and official Amazon listings. Fluke 115 is hands-on tested by OhmSavvy; the Fluke 116 assessment is desk research. How we research.

Key differences

• →Only the 116 reads microamps: 600.0 µA AC or DC at 0.1 µA resolution, the range Fluke built for flame sensors. The 115's finest current step is 1 mA on its 6.000 A range.
• →Only the 116 measures temperature, with a Type K input from -40 to 400 °C and an 80BK probe in the box. Fluke's datasheet and manual list no temperature function on the 115.
• →Only the 116 has AutoVolt with a low-impedance input of about 3 kΩ. Every volts position on the 115 stays high impedance, so it can show ghost voltage on idle control conductors.
• →Only the 115 reads amps through the leads, on 6.000 A and 10.00 A ranges. The 116 has no amp or milliamp range.
• →Capacitance, line voltage, millivolts, resistance, frequency, the case, battery and 3-year warranty are the same on both.

Fluke 116 vs 115 spec by spec for HVAC jobs

Rather than list every range, the table below takes the functions an HVAC technician actually reaches for on a service call and reads each meter's line from Fluke's specification tab.

Flame-rod microamps: the 116's reason to exist

A gas furnace proves flame by flame rectification. The control board puts AC on the flame rod; the flame conducts better in one direction than the other, so a small DC current flows from rod to the grounded burner. If that current is too weak, the board shuts the gas valve a few seconds after ignition. The classic symptom is a burner that lights, runs briefly and drops out, then retries until lockout. The only way to measure the signal is a meter on a microamp range in series with the rod wire.

Flame signals are commonly a few microamps; the minimum each control accepts is set by its maker and is usually printed in the furnace manual. Work the arithmetic on an illustrative 3.0 µA reading. The 116's DC µA line allows 1.0% of 3.0 µA (0.03 µA) plus 2 counts of 0.1 µA, so about ±0.23 µA: easily good enough to tell a healthy signal from a marginal one. The 115 on its 6.000 A range shows 0.000 A for the same current, because 3 µA is a third of a percent of its smallest step.

A low reading usually points to an oxidized rod, a poor burner ground or a cracked insulator rather than the board. Our guide to measuring microamps with a multimeter covers the series hookup in detail.

Temperature and thermocouples

Temperature comes up on almost every HVAC call: supply and return air for a temperature split, a line temperature for superheat or subcooling, a heat-exchanger outlet. The 116 does it with the bundled 80BK probe. Fluke's accuracy is ±(1% + 10) on the 0.1 °C scale, so 10 counts add 1.0 °C; at 13 °C supply air that is about ±1.1 °C, before probe error, which Fluke excludes from the figure. In Fahrenheit the line is ±(1% + 18) at 0.2 °F steps, about ±4.2 °F at 55 °F.

That is fine for a temperature-split check. A rule of thumb many technicians use for cooling is a split around 15 to 22 °F, but the equipment maker's chart wins. Taking both readings with the same probe and meter helps, because a fixed offset largely cancels when you subtract one reading from the other.

The pilot thermocouple on a standing-pilot appliance is a different measurement, and here the two meters tie. It is a millivolt reading, not a temperature reading, and both meters have the same 600.0 mV DC range at ±(0.5% + 2). Open-circuit values in the 20s of millivolts are commonly quoted for a healthy pilot thermocouple; check the valve maker's figure. On an illustrative 25.0 mV reading, either meter is good to about ±0.3 mV. Our guide to checking a thermocouple with a multimeter walks through it.

Capacitors and LoZ on 24 V controls

Run capacitors are the most common failed part on a condenser, and on this job the meters are equal: both read 1 nF to 9,999 µF at ±(1.9% + 2). On an illustrative 45 µF compressor section, read on the 100.0 µF range, the allowed error is 0.86 µF plus 0.2 µF, about ±1.1 µF. On a 5 µF fan section, read on the 10.00 µF range, it is about ±0.12 µF. Either is tight enough to compare against the tolerance printed on the can. See how to test a fan motor capacitor for the procedure.

Control wiring is where LoZ pays off. Thermostat cable often has spare conductors, and long runs sit next to powered ones, so an unused or open wire can pick up a coupled voltage that a high-impedance input displays as a believable number. On the 115, every volts position stays above 5 MΩ, so you must load-test a suspicious reading yourself. The 116's AutoVolt position drops the input to about 3 kΩ, which drains coupling and leaves a real 24 V supply standing.

1. 01

   Odd voltage on a W or Y wire

   Call for heat or cooling is off

   →

2. 02

   116: switch to AutoVolt

   Input drops to about 3 kΩ

   →

3. 03

   Reading collapses?

   Coupled ghost voltage, not a fault

   →

4. 04

   Reading holds?

   Real voltage: check thermostat or wiring

Our guides to testing a thermostat and checking a 24 V transformer cover the control circuit step by step.

Where the 115 is the better HVAC meter

The 115's amp ranges are not useless on HVAC work. Setting the heat anticipator on an older mechanical thermostat calls for the current in the heat circuit, which is a fraction of an amp; the 115 reads it in series on its 6.000 A range, and the 116's 600 µA ceiling can't. Small inducer or damper motors and 24 V control loads can also be read in series. Blower, compressor and electric-heat amps are a different story: they are big, often above 10 A, and sit inside running equipment, so a clamp meter is the right tool with either Fluke.

A technician who works mainly on heat pumps, mini-splits and electric heat, with no gas appliances, never needs a flame-sensor range. If that technician already owns an HVAC clamp with a temperature input, the 115 covers the remaining multimeter jobs and adds amps. Our Fluke 115 review is based on the owner's own unit; the 116 assessment here is desk research against Fluke's published specifications.

HVAC specialist or general-purpose meter?

Fluke built the 116 as a specialist and the 115 as a field-service all-rounder, and the split shows the moment the meter leaves the mechanical room. Off an HVAC call, nobody needs flame-rod microamps, but plenty of jobs need amps: a parked car's battery drain, a bench appliance, a small motor. The 116 has no input for any of them, because its only current range tops out at 600.0 µA. Everything voltage-, resistance- and capacitance-based is identical, so the general-purpose gap is current and nothing else.

The tie in the second chart hides a difference in kind. The two rows the 116 loses are current, which comes up in car, appliance and electronics work every week. The two the 115 loses, LoZ and temperature, are handy but have workarounds: a load across the leads, or a separate thermometer. So a homeowner, a car hobbyist or a general maintenance tech who rarely sees a gas burner gets more from the 115, and our owner-tested Fluke 115 review covers it as an everyday meter. The 116 only becomes the better general meter if you already own a clamp for amps. If you want both amps and LoZ in this body, look at the 117 instead; the Fluke 115 vs Fluke 117 page weighs that step.

Fluke 116 vs Fluke 115 for HVAC: which should you buy?

For HVAC clamps and other meters ranked for this trade, see our best multimeter for HVAC technicians guide. If you are deciding between the 116 and the electrician's model, read Fluke 116 vs Fluke 117.

Frequently asked questions