So there are a ton of "CPU fan not spinning" threads out there, but none of them seem to address this exact situation, nor have any of the users tested the fan connectors on the fan and motherboard. I apologize for the long post, but I figure it would be best to give as much detail as possible without rambling.
My Inspiron 1720 went out on me a few weeks ago. I tried to bring it out of standby, and instead I got flashing LEDs for 45 seconds or so. My Google search led me to the conclusion that it was either my motherboard or my RAM. For a little backstory, I had been getting the following message at boot-up periodically since I bought my machine:
"The AC power adapter type cannot be determined. Your system will operate slower and the battery will not charge. Please connect a Dell 90W AC adapter or higher for best system operation."
I have always used the correct power supply, and since my system performance never suffered and my battery always charged, I just always figured that this was some negligible power-related issue on the motherboard. I ignored it for a while.
Then, about 18 months into ownership, my power adapter started shorting out and eventually bit the dust. I got a new one and after working fine for about 3 months, it started doing the same thing. Refusing to blame my motherboard, I bought 2 more adapters, which again worked fine.
Over these next few weeks I would get random blue screens and quirky system performance. Then, one night I couldn't bring the machine out of standby, as detailed above. Again, after searching Google I learned that it was either my motherboard or my RAM. Remembering my motherboard's history concerning power, I figured it would be best to get a new motherboard.
As fate would have it, there were some newly-listed, genuine Dell 1720 motherboards on eBay for $150 with shipping. I went ahead and got one. When it arrived, I installed it and turned it on, only to experience the same issue as before. Well, I took out on of my RAM DIMMs and it worked again, with one exception: The CPU Fan.
The CPU would not spin at all, not even for a split second during POST. I could get all the way into Windows like normal, but the fan still wouldn't spin. I shut my laptop down to prevent overheating and I figured that the old motherboard's power issues had shorted out one of my DIMMs and my CPU fan. So, I RMA'd my RAM and ordered a new CPU fan.
The parts come in and I install them. The RAM works, but the CPU fan still does not spin. I'm not very knowledgeable of raw electronics, so I got my dad to help me test both of my fans as well as the fan connectors on both motherboards. After hooking the fans to batteries, they BOTH spun, no problem. Then, using a voltmeter, we tested the fan connectors on the motherboards, and BOTH of them supplied power. So, everything works, but for some reason they won't work together. Upon further testing we found the following:
The fan connectors on the fans and motherboards are 3-pin connectors. To make the fans spin when connected to a battery, we had to supply power to the two outside pins slots, 1 & 3. This is the only pin configuration that worked; neither 1 & 2 nor 2 & 3 worked. Then, when testing the connectors on the motherboards, we could only get readings from the pin configurations of 1 & 2 and 2 & 3; not 1 & 3 like on the fans. The opposite!
So, WTH? My guess is that there is some sort of function during POST or perhaps a BIOS setting that tells the motherboard which pins to supply power to in order for the fan to run. I looked over the BIOS for fan-related options but didn't find anything. (I have the latest BIOS, A09, on both motherboards.) I also looked over the motherboard for any jumpers I could change, but didn't find any.
I'm stumped. Does anyone have any input?
Thanks...
My Inspiron 1720 went out on me a few weeks ago. I tried to bring it out of standby, and instead I got flashing LEDs for 45 seconds or so. My Google search led me to the conclusion that it was either my motherboard or my RAM. For a little backstory, I had been getting the following message at boot-up periodically since I bought my machine:
"The AC power adapter type cannot be determined. Your system will operate slower and the battery will not charge. Please connect a Dell 90W AC adapter or higher for best system operation."
I have always used the correct power supply, and since my system performance never suffered and my battery always charged, I just always figured that this was some negligible power-related issue on the motherboard. I ignored it for a while.
Then, about 18 months into ownership, my power adapter started shorting out and eventually bit the dust. I got a new one and after working fine for about 3 months, it started doing the same thing. Refusing to blame my motherboard, I bought 2 more adapters, which again worked fine.
Over these next few weeks I would get random blue screens and quirky system performance. Then, one night I couldn't bring the machine out of standby, as detailed above. Again, after searching Google I learned that it was either my motherboard or my RAM. Remembering my motherboard's history concerning power, I figured it would be best to get a new motherboard.
As fate would have it, there were some newly-listed, genuine Dell 1720 motherboards on eBay for $150 with shipping. I went ahead and got one. When it arrived, I installed it and turned it on, only to experience the same issue as before. Well, I took out on of my RAM DIMMs and it worked again, with one exception: The CPU Fan.
The CPU would not spin at all, not even for a split second during POST. I could get all the way into Windows like normal, but the fan still wouldn't spin. I shut my laptop down to prevent overheating and I figured that the old motherboard's power issues had shorted out one of my DIMMs and my CPU fan. So, I RMA'd my RAM and ordered a new CPU fan.
The parts come in and I install them. The RAM works, but the CPU fan still does not spin. I'm not very knowledgeable of raw electronics, so I got my dad to help me test both of my fans as well as the fan connectors on both motherboards. After hooking the fans to batteries, they BOTH spun, no problem. Then, using a voltmeter, we tested the fan connectors on the motherboards, and BOTH of them supplied power. So, everything works, but for some reason they won't work together. Upon further testing we found the following:
The fan connectors on the fans and motherboards are 3-pin connectors. To make the fans spin when connected to a battery, we had to supply power to the two outside pins slots, 1 & 3. This is the only pin configuration that worked; neither 1 & 2 nor 2 & 3 worked. Then, when testing the connectors on the motherboards, we could only get readings from the pin configurations of 1 & 2 and 2 & 3; not 1 & 3 like on the fans. The opposite!
So, WTH? My guess is that there is some sort of function during POST or perhaps a BIOS setting that tells the motherboard which pins to supply power to in order for the fan to run. I looked over the BIOS for fan-related options but didn't find anything. (I have the latest BIOS, A09, on both motherboards.) I also looked over the motherboard for any jumpers I could change, but didn't find any.
I'm stumped. Does anyone have any input?
Thanks...