I've had my HD70 for 4 months and about 4 weeks ago I got a "fan failure" message and it hasn't worked correctly since. I can turn on the PJ and after about 15 minutes the message pops up and the PJ turns itself off along with the red light turning on. I have taken it apart several times in an attempt to clean it out and the problem still persists. I don't believe that it is the actual fans (there are two inside, both sunon fans) that are causing the problem, nor do I think it is overheating because I have taken the front cover off and put a huge fan next to the front and when doing so the PJ runs almost cool. It may be the controller board but I can't find any info on how to get that part or how much it costs, or if its even truely the problem. The bottom line is I'm out of warranty and I want to fix this myself due to the fact that I'm low on funds at the moment. If someone, anyone, could please give me some insight on this issue it would be GREATLY appreciated! This is truely my favorite item in my home and I feel naked without it:) Thanks for your time.

Its been a while since i've been in an hd70, but i remember that there are two fans dedicated to cooling the lamp, one is a blower type fan and is buried a bit under the main board, and then there is another fan, the regular type, toward the ballast blowing onto the lamp also. I don't recall any other fans existing beyond those two, but i could be wrong.
What you need to do is start the projector up and see what fan doesn't start. Visually, i don't mean listen or anything like that, but you need to verify if each is actually spinning.
In the hd70 a fan failure means a failure to read the fan power or rpm (i am not sure which the fan is manufactured to do, i'd assume rpm for proper cooling) given by a third wire on the fans cable. So, if you have ensured (very important so you don't waste your time) that the fans are still running, you need to make sure the third wire on each is not frayed and still carries a current from one end to the other. And if that fails, then it probably is a controller issue.
I would get this error when the plug for the ballast/lamp fan cable was a bit worn. I ended up having to find a replacement plug to use and rewire onto the cable.

First off I appreciate the reply. Both the fans are working and the wiring for both seem fine. I just opened it up again and and looked for what you told me and it doesnt seem to be the issue. Due you know how much a contoller board for the HD70 costs? I'm having a local business look up the price for me but it could take a while. You mentioned something about the ballast and the end of you message, could that be an issue with my PJ? Anymore help or ideas would be great. Thanks again!

The main board for that model is around $580 - 600. Finding someone to sell it to you is another matter. Optoma, like most, if not all other manufacturers, won't sell parts to end-users, neither will my parts sources. You have to be a service tech.

And you have to be sure that is your problem, parts like that are not returnable.

You might want to scour the net for a used or broken unit with other issues that you can use for parts.

Thanks for the advice. I feel totally screwed! I guess I pretty much got ripped off for $800 for a PJ that worked for 4 months. I find it crazy that one can't find any info on "fan failure" issues with this model. I honestly have no clue what to do next. The thing that sucks is I didn't just spend the money on the PJ I spent a whole lot of money on the room that its in that no one goes into now. Beware of ebay PJ's my friends!

I just watched both fans while the "fan failure" message popped up and noticed that one of the fans stopped working at that very moment while the other continued to run. Do any of you think that the one fan that stopped working could have an issue while the other is fine?

Thanks for the advice. I feel totally screwed! I guess I pretty much got ripped off for $800 for a PJ that worked for 4 months. I find it crazy that one can't find any info on "fan failure" issues with this model. I honestly have no clue what to do next. The thing that sucks is I didn't just spend the money on the PJ I spent a whole lot of money on the room that its in that no one goes into now. Beware of ebay PJ's my friends!
Although i hate to say it, you could have gotten a better projector for $800. Heck, you could even have gotten a new hd70 for that price (i've seen some leftover stock of hd70's going for $600 at some places)...
And if you're sure the cabling and the fans are in working order, then it most likely is the board. Though, technically the fans may still spin but may not be able to keep the needed rpm, triggering the fan failure... but that is less likely than it being the board.
Your best chance right now would be to find an hd70 that is used or broken that is going for cheap and scrapping it for parts. Or cut your loses now and go for another projector.

I just watched both fans while the "fan failure" message popped up and noticed that one of the fans stopped working at that very moment while the other continued to run. Do any of you think that the one fan that stopped working could have an issue while the other is fine?
It could be the bearings going bad causing a hiccup every once in a while, or the motor burning out. If the controller tracks the fans rpm, then that may be the case for the warning.
Compared to the rest of your options. a quick fan replacement would be a cheap thing to at least give a try. So i'd try that first before you explore any other options. Which fan stopped? The blower or the regular?

It's possible that one fan is bad. It is unlikely, though. I've had a number of fan failure incidents in several Infocus projectors and in each case, it was the controller that failed.

It's the blower fan that stops when the fan failure message pops up.

Get a 120mm 12v fan used in computers and strap it to the PJ so that it cools your PJ and you can get the 12v power off of the 12v trigger output on the PJ used for electric screens.

Get a 120mm 12v fan used in computers and strap it to the PJ so that it cools your PJ and you can get the 12v power off of the 12v trigger output on the PJ used for electric screens.
Problem is, the projector will still think the fan is dead. Its not a temperature problem as much as its a sensor problem. The projector controller, is sensing either power or rpm problems with the fan by use of the 3rd wire. If we could figure out how to fake out the controller we could do the separate add on fan idea though.

Problem is, the projector will still think the fan is dead...
Ah, right you are - that stinks.

It could be the rpm sensor in that fan is bad....although usually they'll shut right down if thats the case. Can you wire in a normal (same voltage) pc fan to that plug and see if stays running? Assuming its a standard 12 or 5v 3 wire fan w/ rpm sensor?

Try to find an exact match of the fan on digikey/mouser and replace it. Note the models have to be the same as there are different types of sensor boards for each models; failsafes, readings, etc. If all else fails contact Sunon! Try to indentify both of the fans and get them both replaced.

Ah, the greatness of the web! Someone suggested setting the pj to "High Altitude".
Worked for me :):)