HoneywellM847D1012 Actuator, Spring Return Direct Mount Two Position 24 Vac

Ordered last night at 8pm, was on my doorstep this morning at 11am with free Prime Same-Day delivery! Thanks to reviews on Amazon and videos on YouTube, I was able to determine for certain that this was the correct replacement for a Trol-A-Temp RDMH damper motor (made by Honeywell). One star off for Honeywell not making replacement motors simple to find on their web site and for including what looks to be 27th generation photocopied instructions from 1956. Our original damper motor was 15 years old and I guess we're lucky that it lasted so long based on some of these reviews. We have a three zone system, so I ordered two actuators and will just keep one handy as a spare. For eighty bucks, it's cheap insurance. Replacement was ridiculously easy - disconnect wires, loosen the set screw with a 1/8" allen wrench, remove, replace, tighten the set screw, connect wires, done! Just remember that if you have to crawl through a confined space to make the repair, in addition to your tools, BRING THE NEW PART!!!

I have a three zone HVAC system and started to have problems with the dampers. The first time was a $90 technician call and all he did was "free" the damper. Started having some other problems and a closer inspection found that the damper was not working correctly. Purchased one of these and replaced one on my system. Works great. On closer inspection of the old unit, I noticed the nylon gears had worn badly and the motor gear was skipping on the drive gear creating a clicking noise.While inspecting the replaced one, heard the tell-tale clicking from another damper. Replaced this one as well. The third one in my system in still working(8 years), but it is only a matter of time before it fails so I purchased a third one and I'm ready when it does. As another reviewer mentioned, the replacement is a piece of cake (one set screw and two wire nuts)and it sure beats paying the technician. There is no telling what he would charge for the part.Like another reviewer, I'd like to have a better unit, but that may involve a different damper and different programming on my system, so this is the easy fix. Glad Amazon had these available at a good price and quick shipping.

Just be aware, these specific M847D Honeywell Actuators have a built-in failure point: The larger gear (the driven gear) that is connected to the return spring is made from a plastic material, perhaps phenolic. This forms the gearset with the actuator motor, on which the pinion (driving gear) is mounted. The failure occurs when the plastic teeth on the larger gear finally break off and form a "dead" spot which prevents full rotation of the output shaft. When powered, the motor begins to rotate the driven gear, only to encounter the missing teeth. This produces a "clunking" or "clicking" sound which continues until the actuator is de-energized by the system control. The zone controlled by the actuator is left in the "normal" position, which might result in no airflow, or constant airflow, depending on whether it is "normally open" or "normally closed".This is a glaring design flaw. This gear could easily be replaced with one constructed from powdered-metal or similar material. That would surely result in a longer life product. I have replaced the same actuator on my home HVAC system zone damper FOUR (4) ! times in the last 10 years. I started doing it myself after paying the HVAC guy $260 the first time! Wish there was a better device for this purpose, but I'm not an expert.

I have a 3-zone HAVC system. The actuator for one zone failed, so I bought this.Service from Amazon was of course excellent.The actuator stumped me, and I had to call a furnace repair guy who (a) spent 20 minutes tutoring me and (b) charged $170. He said, "We'd charge you about $250 for the actuator + the $170..."Notes to others:1) The voltage is 24 v. AC.2) If the actuator doesn't work, loosen the damper limiter on the back of the actuator.3) Polarity of the wires doesn't matter. I labeled wires when I took off the old actuator. The furnace guy ignored my labels and hooked up the new actuator opposite of how the wires were marked.4) It's important to know if your damper is open or closed with power off.5) According to the furnace guy these actuators are very reliable. If there are repeated actuator failures, replace the damper, something that is easy to do.

Not really impressed. Used to "zone" different areas of a home or space, these actuators see ?X? number of actuation's per day. They are spring return and I install them to spring return to the open position - to insure a space gets heat if the unit fails or power is lost to the unit itself. (fail safe) Very much depends on the design and installation of the system but the springs break, the units stick and you have some zones going beyond the temperature setting and other zones failing to meet the temperature setting just because the failed unit is taking all of the heat / cooling. Although this is the expected result and a troubleshooting tip, it's an undesired outcome. I feel that "Honeywell" is capable of manufacturing a much better product for the price. It's a dependable name on an unflattering device in my opinion.

I was sure our thermostats were wired wrong or that there was a problem with the HVAC system because we were getting forced air from the A/C and furnace in rooms that were not controlled by the thermostat that was on! By coincidence I happened to read that someone else had that issue and they had replaced the actuator that controls the flow of air in one of their ducts because it was not working and the duct was stuck open. This was my problem! I ordered 4 of these and it took me about 20 minutes for each to replace including cleaning the vent, re-taping with aluminum tape, and connecting the wires. My system now works perfectly. These are excellent units and all my zones now work perfectly.

Money spent is worth while for this product.