# Load profile of a headlight **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [November 5, 2023, 3:07am UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720 "2023-11-05T03:07:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 5, 2023, 3:07am UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/1 "2023-11-05T03:07:41Z")
My computer stopped working. I’ve narrowed it down to the power supply or the motherboard. The PS delivers the right voltages, but I can’t load it enough to test at rated current (12A). (I’d need a 1Ω 150 watt resistor.) I hooked it up to my heat gun, 10Ω, and it delivers 1.2 amps to that, but that’s the biggest load I have in house. Then I remembered my pickup’s headlights: the high beam is 65 watts, about 5Ω - 5.5A; I think that’s a big enough load. But I think that’s when it’s on, warmed up, that it draws a lot more current to get warm first. ---
**Author:** ![LoudThunder](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/loudthunder/32/27769_2.png) [@LoudThunder](https://community.cartalk.com/u/LoudThunder)\ **Post date:** [November 5, 2023, 3:52am UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/2 "2023-11-05T03:52:43Z")
First off, did you check the input fuse? The computer power supplies that follow the ATX convention output +3.3V, +5V, +12V, and -12V, and it’s all DC. Does you heat gun function normally with DC verses AC? Most Power Supplies that fail, FAIL… usually one for more of the fuses, bridge rectifiers, diodes, or a field-effect transistor (FET) dies or they burns up ( and you usually can smell something strange ) But when this happens, it’s not intermittent and it fails completely, if you are still getting the specified voltage from the various plugs; it’s working… Have you eliminated all other possibilities, loose connections, bad cables, depending on the age and make of your mother board, some odd ball MBs stopped booting if the clock battery died since it did not get a time sync? Finally, if you decide trying to track down the problem isn’t worth it; it’s a great time to buy a new computer, it seems that all the major big box stores are already advertising early Black Friday sales… ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [November 5, 2023, 2:38pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/3 "2023-11-05T14:38:33Z")
I don’t get why all the gymnastics- > [@RandomTroll](#): > > My computer stopped working. OK, it’s not working, that’s definitive. > [@RandomTroll](#): > > I’ve narrowed it down to the power supply or the motherboard. The PS delivers the right voltages, but I can’t load it enough to test at rated current (12A). (I’d need a 1Ω 150 watt resistor.) The motherboard IS the load (along with all the other devices connected to it). Who cares if it can deliver full rated current. If it’s connected to the ACTUAL load and the voltages are correct but the computer still won’t fire up, you need to start looking elsewhere. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [November 5, 2023, 2:39pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/4 "2023-11-05T14:39:08Z")
Isn’t a PS pretty cheap? ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 5, 2023, 4:33pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/5 "2023-11-05T16:33:51Z")
> [@LoudThunder](#): > > did you check the input fuse? The fans spin up; the power LED flashes, then it turns itself off. It delivers 1.23A @ 12 V, .51A @ 5.08, .31 @ -12V (! - it’s rated to only .2, so I overloaded it. And it’s only for the serial port, which I don’t use.) - why check the fuse? > [@LoudThunder](#): > > computer power supplies that follow the ATX convention It’s not ATX. > [@LoudThunder](#): > > Most Power Supplies that fail The PS testers others have recommended just put an LED across the outputs; they agree with you. > [@LoudThunder](#): > > Have you eliminated all other possibilities Yes. It happens even if I remove the motherboard from the computer, take off the RAM, take out the CPU, disconnect every cable that connects to it. That’s what I meant when I wrote that I had narrowed it down. > [@LoudThunder](#): > > it’s a great time to buy a new computer Big spender. > [@TwinTurbo](#): > > If it’s connected to the ACTUAL load and the voltages are correct but the computer still won’t fire up, It fires up, then powers down, then restarts, every 5 seconds. It acts like a device that has exceeded the rating of its power supply > [@Cavell](#): > > Isn’t a PS pretty cheap? New ones run $70-$120. I can buy an untested used on eBay for $14. I can buy a barebones computer of the same model for $26 - and it’s been tested. I got my computer support from LinuxQuestions. I asked about using a headlight as a load. That’s the question I asked here. > [@TwinTurbo](#): > > I don’t get why all the gymnastics- Fun. If responding wasn’t fun for you you shouldn’t have. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [November 5, 2023, 5:19pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/6 "2023-11-05T17:19:28Z")
Have you tried booting from a usb?? ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 5, 2023, 5:52pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/7 "2023-11-05T17:52:47Z")
> [@Barkydog](#): > > Have you tried booting from a usb?? Of course, but it doesn’t even get as far as loading the BIOS setup, much less loading anything from disk or usb drive or even RAM. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [November 5, 2023, 8:12pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/8 "2023-11-05T20:12:48Z")
Got a power supply I can sell ya, failed try to revive a computer. New thermopaste on processor? Free pickup SE WI, 1/2 purchase price. ![Powesupply1](https://global.discourse-cdn.com/cartalk/original/3X/e/8/e8b370a4b4fb1a28d9a31400d193331b5d549a8a.jpeg) ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [November 5, 2023, 9:01pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/9 "2023-11-05T21:01:00Z")
Heh heh. My last computer was a thermotake. The fans were so noiseyz I had to replace them. When the machine went south, Dave wouldn’t work on it so I just bought a new computer. Those magnets in the hard drive are something to behold. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [November 5, 2023, 9:42pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/10 "2023-11-05T21:42:59Z")
> [@bing](#): > > Those magnets in the hard drive are something to behold. Super magnets they are, I have a bunch I harvested at work. The interesting thing is they are super strong magnet on one side, then nothing on the other. Looking to build a perpetual motion machine. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 5, 2023, 9:53pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/11 "2023-11-05T21:53:18Z")
I use several discarded car headlights to load- test computer power supplies. In this area folks throw their computers away all the time. They just put them out on the curb for anyone to take. If I need a lab power supply for some reason I’ll grab one, take it home & and extract the power supply, easy-peasy way to +/-12, +5, +3.3 vdc, delivered at a considerable power rating for the lab bench. BTW, this method isn’t entirely safe. Old computer power supplies may have high leakage current. I always measure the leakage current before using them. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [November 5, 2023, 10:01pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/12 "2023-11-05T22:01:39Z")
We have to recycle ours for about $20. ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 5, 2023, 10:29pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/13 "2023-11-05T22:29:32Z")
> [@Barkydog](#): > > Got a power supply I can sell ya, failed try to revive a computer. New thermopaste on processor? Free pickup SE WI, 1/2 purchase price. Thanks. It’s the wrong footprint, expensive at $27.50. > [@bing](#): > > magnets in the hard drive are something to behold. I have an SSD now. It’s worth the money, not that I paid anything for it. > [@George\_San\_Jose1](#): > > I use several discarded car headlights to load- test computer power supplies. DING! DING! DING! We have a winner. Thanks, @George_San_Jose1 . What resistance do they measure cold? I worried that they could be 1Ω, draw down a computer power supply enough to cause it to shut off before the bulb warmed up enough to raise the resistance to operating. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 5, 2023, 10:31pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/14 "2023-11-05T22:31:47Z")
> [@RandomTroll](#): > > What resistance do they measure cold? I’ll measure the cold filament resistance and report back. Whatever it is, the power supply has no trouble powering them up from cold. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [November 6, 2023, 2:14pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/15 "2023-11-06T14:14:14Z")
> [@RandomTroll](#): > > It fires up, then powers down, then restarts, every 5 seconds. It acts like a device that has exceeded the rating of its power supply What happens to the supply output voltages when this happens? Normally, when you initially apply power to the computers I have with soft start, they will do exactly this and then immediately shut back down. When you press the power button, it then wakes up and goes through the normal boot process. There could just as easily be something wrong with the soft start circuit making it look like the button is continuously pressed. But diagnosing it while connected would be the route I would take. > [@RandomTroll](#): > > Fun. If responding wasn’t fun for you you shouldn’t have. I come here to contribute because I find it fun and occasionally I may even help someone. So doing all this extra work that may have no diagnostic benefit is fun for you? Great, have at it. I thought you might be interested in solving a problem in the most expeditious way. I find fixing things generally fun but I usually don’t perform diagnostics for fun. Carry on… ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 6, 2023, 9:27pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/16 "2023-11-06T21:27:10Z")
> [@George\_San\_Jose1](#): > > I’ll measure the cold filament resistance and report back It’s difficult to measure low ohm’s accurately , but my estimate for the cold filament of a 9001 bulb I test with is 1/2 ohm. I think that’s the high beam, but not sure. My power supply has no trouble with lighting it up on the 12 volt lead. It has these power outputs - 5v 16 amps +12 v 10 amps +3.3 v 18 amps Total output power limit, 170 W. ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 6, 2023, 9:35pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/17 "2023-11-06T21:35:28Z")
Thanks; you’re a friend. May I borrow one? ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [November 6, 2023, 9:42pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/18 "2023-11-06T21:42:18Z")
> [@TwinTurbo](#): > > What happens to the supply output voltages when this happens? They rise to rated value, then fall off to near zero, then start over. > [@TwinTurbo](#): > > when you initially apply power to the computers I have with soft start Some this computer lacks. The power button doesn’t matter. I disconnected it: the same happens. > [@TwinTurbo](#): > > doing all this extra work that may have no diagnostic benefit is fun for you? I started this on LinuxQuestions. Only after mulling it over did I realize I had only one load below 10Ω that would handle the current: an auto headlight. I’m pretty sure it’s the motherboard; contributors on LQ lean to the PS. I wanted to answer the question, not just fix the problem, and at the least cost. It would be elegant to replace the PS for $14; it would be more expensive if wrong. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [November 7, 2023, 12:20pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/19 "2023-11-07T12:20:55Z")
> [@RandomTroll](#): > > They rise to rated value, then fall off to near zero, then start over. The simplest test you can do is to disconnect everything from the PSU. Does your PC cabinet have a secondary fan? You can reconnect this fan or use one of the auxiliary devices as a load on the supply. Look at the motherboard connector from the PSU. The single green wire is the enable signal that comes from the motherboard to the PSU. Use a bent paperclip to connect the pin with the green wire to any black wire pin in the connector. Now try powering on the supply. If it turns on and runs its own fan and the load fan/device without cycling on/off, the problem may be elsewhere. If it still cycles, the power supply is bad. ---
**Author:** ![TheWonderful90s](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/thewonderful90s/32/29584_2.png) [@TheWonderful90s](https://community.cartalk.com/u/TheWonderful90s)\ **Post date:** [November 8, 2023, 2:35pm UTC](https://community.cartalk.com/t/load-profile-of-a-headlight/193720/20 "2023-11-08T14:35:32Z")
Are you able to measure the 3.3V 5V and 12V supply Voltages while attempting to turn the computer on? Most people just swap in a different known good power supply to test to see if it’s the board. Power supplies are supposed to have a minimum load on each output. Usually you can get away with not doing that, but I’ve blown out the 3.3V regulator by loading down the 12V and leaving the rest disconnected. You said a regulator on the motherboard is bad. That’s quite possible. It could be the power supply for the CPU or memory. [Next page](https://community.cartalk.com/t/load-profile-of-a-headlight/193720.md?page=2)