You're correct, your downstream levels are to low. Typically the reason for this is that there are too many splits in the signal before the modem. Try eliminating any unneeded splitters or if it's possible, try your modem on another outlet. There are other issues that may cause your downstream levels to go bad, you might need a tech to figure it out.
See the troubleshooting guide.
The technician used one 2 way splitter inside the house. it was reading -10dbm when it was installed which I told him it seemed really weak but he said it would be fine. he said the mainline was reading around -5dbm. and after the splitter it was gonna be ok. he guaranteed me that the signal would be fine. is -5dbm from the mainline too low? seems like the temperature is changing the signal levels too as its getting hotter now.
Yeah, you should be seeing positive values where the line enters your house. If you have -5 dBmV at the side of the house you'll lose 3.5dB from a 2-way splitter and then a little more loss from the coax. So a -10 dBmV at your modem would be about what you would see. You'll probably need a tech to get this resolved.
I've asked a Comcast employee to help you. You should expect a reply in this thread.
I can help get a tech out for you. Can you please verify your first and last name, full street address, and the phone number or account number associated with your services in a private message?
To send a private message click on my name "ComcastChe", then click private message me.
Yes, I feel 100% better. Thanks. I've just replied. letting you know what I would recommend for the issues I see on your account. Let me know how you would like to proceed.