Introduction: Epson Projector Temperature Sensor Repair
This is an instructable for how to repair an Epson VS210 projector when one of the temperature sensing thermistors stop working.
The projector goes into an overheat protection cycle, where after running for 30 seconds to 2 minutes, the bulb shuts off and all three fans ramp up to maximum speed. The fans stay on for about 2 minutes then the projector shuts down. During this, the red "temp" light flashes.
This is not a plugged air filter! Epson's online help for a case like this places the blame on the user and poor maintenance. Some users have plugged air filters, and when the filter is cleaned, the problem is corrected. This is a manufacturer's defect, tiny cheap sensors. Epson's website does direct you to an "Authorized Service Center" but the website would not load for my region. I don't think service is a real priority for Epson.
The key here is the unit is not overheating, the bulb has been on for only moments, and the unit is cold. This is a failed thermistor sensor, which shuts down, and renders the whole projector useless.
Instead of throwing it out, and buying a new one, we can repair it. The best option would be to replace the failed sensor with an OEM Epson replacement part. However these are very difficult to find, and expensive. Electrical components are cheap, and this is a cheap fix.
This was not the most expensive projector, it was a few hundred dollars on sale. But failed temperature sensors seems to be a somewhat common problem on Epson projectors. People are throwing out much more expensive projectors than this one!
Step 1: Open Up the Case
From looking online, all Epsons look alike on the inside. There is a lamp, 3 fans, and 2 temperature sensors (some may have 3), mirrors, prisms, three LED screens and a lens.
I figured, the bulb still worked, and all three fans worked as well, so this must be a sensor problem.
Epson used thermistors to measure the temperature because they are very cheap, and they do a good enough job. A thermistor is a type of resistor whose resistance is dependent on temperature. They produce a non-linear reading. When I measured the resistance across the thermistor leads at the connection to the board, I had zero ohms at the intake sensor. I forget what the measure was at the exhaust thermistor, but it was not zero. A return of zero ohms from a thermistor means infinite temperature. So the Epson processor must have interpreted this as superheated air entering the fan, and shut down, throwing a temperature alarm.
Step 2: Temporary Fix
My original plan was to replace the broken thermistor with a working one from my collection of random electrical components. I was concerned this thermistor might be for a very specific temperature range. I could take a guess at what Epson thought intake air temperature would be. Turns out I couldn't find a thermistor, and at this point I thought this was a long shot anyways, so instead of using a thermistor I took it one step simpler and just used a resistor. I think this one was 200 ohms, another shot in the dark. Looking back, I should have chose one more like 10,000ohms.
Anyways, wouldn't you know it. The projector starts working. I let it run for 5 minutes before I unplug the resistor to see if this is the fix, or its just a coincidence. As soon as I pull it out, the bulb shuts off and all three fans go into high speed mode. Looks like we got it narrowed down!
Without the resistor, the projector would last maybe 5 seconds before shutting down and blasting the fans, so 5 minutes is impressive. I reconnected the resistor, pointed the projector in a less annoying direction, turned it on, and left it on for 2 hours. No problems.
Step 3: Permanent Fix
There is nothing as permanent as a temporary fix.
I decided against finding a replacement thermistor and just bypass the old thermistor with a resistor. I cut the wire leads leading to the thermistor and soldered in resistor. I plugged it back into the board and tucked the lead under the circuit board.
I plugged the projector in and tested it before I put the case back on. We even watched a movie with it like this. Worked fine.
Step 4: Final Thoughts
Ultimately this is not the best fix. I justified bypassing the sensor because the intake air temperature is a little redundant compared to the exhaust air. If the projector is really overheating, it will be the exhaust temperature that registers it, and shuts it down.
I wrote this out of frustration with Epson. They have a total lack of support to fix, or even diagnose a problem with their product. Thermistors are incredibly cheap, and an OEM making one to last should not be hard. Also, reading online, other people have the same issue with these sensors, it seems to be a recurring problem.
This projector was not very expensive, I think it was $300, but we really haven't used it very much, maybe 100 hours of watching movies on it, its supposed to last 4-5000 hours. Looking online, people were throwing away Epson projectors that cost $2000 because of this. This fix cost me nothing except for my time. In my case I already had the resisters, but to buy one resistor would have been cheap.
The answer always seems to be "Just buy a new one". Since Epson is the largest supplier of projectors, any replacement would probably from Epson. Demand Better! If manufactures build a sub-quality product, do not just buy another one from them! Fix it and keep using it.