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  • Heat preventing system boot...

    I have a CarPC in my trunk and with outside temperatures in the 90s(f) my PC will not even attempt to boot. I have to fold down my rear seats and blow A/C back there for a while before it will boot. The computer case in fact is near scalding temperatures. I haven't used a temp probe on it yet, but I'd guess it's 130 or so. I have gone into the trunk and tried to turn the PC on when it's this hot and the CPU fan comes on for less than a second and then immediately shuts off. My assumption is that the motherboard is preventing boot because of the temp. Other people have noted errors or crashes, but mine just does not attempt to boot.

    I'm interested in what others have had to do for their PCs to boot in this kind of heat.

    I've searched for the past couple days and haven't found a real solid answer, although I've read about several people having the same issue. The discussions always get side tracked though on overly complicated cooling setups that only work with the computer running. Like big heatsinks or water blocks. Once my PC boots, the stock heatsink brings the system to a perfect operating range. What I need is to cool the PC BEFORE it turns on. Or keep it at least a little cooler while it sits in the parking lot so it'll boot and let the stock fan and heatsink do their job. I don't need the trunk to be comfortable, I just need it less than boiling.

    The other discussions I've found all have some variables that confuse the issue and so I want to set some global variables to work from.

    The question is how to make sure that the PC boots after sitting in a parking lot all day in the sun.


    1. The car is stationary
    2. The temp outside is 110 degrees F
    3. The car cabin temp is 125 degrees F
    4. The trunk (boot) temp is 140 degrees F

    For the purpose of brainstorming, I'm not worried about running down a battery because I can control this with shut off switches or something that turns itself on and off instead of staying on constantly. That is a seperate hurdle and can be addressed easilly with low-tech means. (such a device like a battery buddy - a DC power monitor that triggers a relay to shut off the power drawing device)

    Re-directing A/C to the trunk or using fans to move air between the cabin and trunk are ideas that require the car to be on or require the cabin temp to be conditioned first. In the first several minutes after getting into my car the cabin temp will be far too high still to use as a cool air source for the trunk. And while I could use A/C to cool the trunk after I start moving, I'd have to wait until the trunk cools and then boot the PC manually instead of the power controller doing it for me. This is not much different than what I do now, so why do anything if that's the solution?

    Maybe my system would boot at 125, just not at 140. Maybe making the trunk temp equal the cabin temp would do the trick. Has anyone actually just vented to their cabin and had that work?

    A temp probe and a hair dryer to test operating temps will answer that question scientifically, but for now the assumption is that the cabin temp is still too high to allow the PC to boot.

    My searching has come up with 3 basic ideas.

    1. Vent trunk to cabin - this idea sounds like it has a small chance of working. But if the cabin temp is still too high, then this effort will have no effect on the problem.

    2. Vent trunk to outside - this idea has the same drawback as #1 if the outside temp is still too high or the air is just too hot to effect the trunk air temp enough. Pumping 110 degree heat into a 140 area won't drop it to 110. It'll be somewhere in between and probably still too hot to boot.

    3. Peltier cool the trunk - this idea presents some complicated challenges in fabrication, but people get stuck on a condensation issue with this and even the A/C options. However, condensaton is only a problem if you cool down to a dew point. That's far from what would need to be done.

    Consider the fact that applying a small amount of 50 degree cool air to the trunk via a peltier would NOT bring the trunk and PC all the way down to 50 degrees and therefore produce condensation on the PC parts. It might however drop the 140 down to 80 or 90. And that would be a temp that I could boot at for sure.

    Condensation would form on the peltier itself for sure. But I'm not talking about puting the peltier on the CPU or in fact anywhere close to the PC. The peltier would be up in some corner like a fan on a shelf next to your desk at work. It would produce cool air and just blow it towards the PC, while a vent fan vents to the cabin maybe so as to complete the air path.

    This does present two challenges though.

    1. Dealing with the hot side of the peltier - this could be dealt with by mounting the peltier in the lid of the trunk with the actual heat side of the peltier (or just it's heatsink) outside the trunk. This would entail cutting a hole all the way through the trunk and making some kind of mount for the peltier where you end up with the heat side external and the cool side internal. Doing this safely and cleanly are side issues, but I think it could be done well with enough thought.

    2. Dealing with the condensation inside the trunk. Simply mounting a catch tray with a sponge should be sufficient to catch the drops off the internal heatsink for an 8 hour period (or certainly for a 30 min period if you use a timed turn on) and the sponge can be wrung out every night or something if it really gets that wet. Catching the water in this way will prevent to some degree the trunks overall humidity as long as the sponge is inside an enclosure with only a small part exposed to catch the drip.

    My other thought for the condensation might be simply mounting the peltier in the floor of the trunk and making a second hole for a drain so the water simply drops off the peltier and down the drain onto the pavement outside.

    Even if a safe and clean install could be done this way, power is then the issue. How long could a car battery power a peltier? Only real world tests will find out for sure, but even if you could get 30 min out of it, surely that would be sufficient to cool the trunk to under 100 degrees. Remember the goal is just to lower the temp enough to boot, not to make it comfortable in there. A timer could turn on the peltier every day 30 min before lunch and 30 min before I go home. Then only run for 30 min and shut off to protect the battery.

    Thoughts? Suggestions? Anyone actually had the same problem and have it fixed now?

    Thank you in advance!

  • #2
    I've got this exact same problem. I've been fiddling with sollutions for 3 years. I haven't found anything yet though. I've got a BMW that's well insulated (for sound reasons) that I kind of killed because I removed part of the truck carpeting to house the computer, thus exposing bare metal that's directly heated by the sun (and is 4 inches from the computer)

    My next step is to re insulate that area near the computer to keep the direct thermal radiation from the hot metal from warming the computer components. At least I'll make it heat up an insulation shield first. That should take out a good amount of the thermal energy.
    Here it is! My carputer install! 1997 BMW M3


    • #3
      Well my pc right now is mounted to the floor of my trunk, but it's not really that close to the metal of the car. My 'floor' is a cardboard piece that serves as a lid for the spare tire well. So my PC sits 8-10 inches above the metal bottom of the trunk with a spare tire, a layer of cardboard, and a layer of carpet in between. I currently have the PC velcro'd to the carpet.

      So I don't think I'm picking up much if any heat from a direct transfer like a lot of people do.

      I am moving my PC soon though as soon as my new speaker boxes come in. I'm moving my subs to the back corners of the trunk and mounting the PC to the back of the rear seats. Thus it'll move up and away from trunk floor and closer to the cabin, but I don't think this will change my problem much if any because even the cabin gets to about 120 sometimes.

      It will give me the added advantage though of folding down the seats and bringing the PC into the cabin though. So if nothing else at least I can cool it down quickly and then flip the seats back up. I only need the PC to boot, then it's own fan keeps it running. I've got bios set to shut down if the CPU gets to 180(F) and so far it hasn't ever shut down.

      There must be a different temp level preventing boot though, because while I would believe that the cpu and case are 130-140 at times, I can't imagine them getting to 180 while powered off.


      • #4
        Could be ambient board temp that is stopping it from booting. If you have the space in the case put a fan in connected to the normal 12v car voltage. This would let you blow air through the case and cool it down. You could even hook it through a relay controlled from your power supply so when your PC boots the extra fan is shut down keeping things quieter.
        Visit my site V8 Scimitar

        SP13000, 300GB SATA HD, 1GB DDR. Opus 150, K301 screen, Cisco WIFI, AQmax GPS, RoadRunner and FreeDrive, Sony MEX-R5 head unit. 4 years installed and it just keeps running!


        • #5

          Are you windows tinted?

          I found that tinted windows significantly reduce the temperature of the whole cabin including the boot area.


          • #6
            Originally posted by wywywywy View Post

            Are you windows tinted?

            I found that tinted windows significantly reduce the temperature of the whole cabin including the boot area.

            What kinda hardware you running?
            I see those kinds of temps a few times a year here in TX, never been a issue.


            • #7
              My specs are in my profile on the left there.

              What PSU do you guys have powering your CarPC?

              My windows aren't tinted just yet, it's a new car and that's a list of things I plan to do. I need to replace my winshield first though before I tint, it's got a crack on the passenger side. No sense in tinting until I replace that.

              Now that I'm using my temp probe I'm finding that the trunk is actually cooler than the cabin by 5-15 degrees. This makes my initial set of globals invalid.

              Yesterday afternoon it was only 85 outside, 115 in the cabin, and 100 in the trunk (computer case metal was 100 as well) and the system would not boot on it's own. However I don't think it was a temp issue yesterday because the CPU fan stayed on this time and a hard reset by me let it boot.

              I'm starting to suspect the M2-ATX PSU to be the problem. It's had it's issues anyway previously and so I'm using it in an unorthodox way. It may simply be on it's way out or maybe it's the part that doesn't like the heat.

              Because the M2 wouldn't consistantly boot my machine, I unhooked it's power button wire and left the case power button hooked up. I just let the PC stay on when I exit the car and the M2 kills power hard after 2 hours. Then I have bios set to power recovery and the PC boots on it's own when power comes back.

              Every now and then though, the M2 does what happened yesterday. It seems to turn on the 5V rail but not the 12V rail because the CPU fan comes on but the PC itself doesn't. All I have to do is hold down the case power button to kill power, then wait a few seconds, then hit the power button to boot.

              I'm in the market for a new PSU though, so maybe my issues will just go away.

              The times it's been really hot though, like 140-150 in the trunk, I've witnessed the CPU fan coming on and then turning right back off, even after several hard boot attempts by me. When that happens, I've had to wait until I can cool the trunk down to try to boot again.