Just changed the batteries of my Honeywell RCT 8100A after a long off-season, and I can't figure out how to reprogram it. Where can I find a user's guide?

The batteries must be installed before using your safe. The battery compartment is located inside the safe on the lock cover panel.
Note: If both green and red LED's are on, it is an indicator that the batteries are weak and must be changed immediately. The User Code will not be erased if power is restored by replacing the
batteries within 30 minutes. After 30 minutes, the User Code will be erased and will need to be reprogrammed. Weak or dead batteries should be replaced immediately and all 4 batteries should be changed. To replace the batteries please follow STEPS 1 - 3. Remember to always remove batteries from safe if not using for an extended period of time. If your batteries are completely dead and you cannot o pen the safe by using the digital keypad, use the override access key to open safe
and access the battery compartment. The use of Non-alkaline or rechargeable batteries is NOT
RECOMMENDED.

Louise try removing batteries for 10 minutes, and reprogram,
manual link below , press the helpful button
Honeywell RTH8580WF User Manual

http://www.gogeisel.com/geiselonline/support/Honeywell/CT3300_CT3355.pdf this is the programming manual- they have a note that if you show low battery after replacing the battery- put the battery in backwards, wait 10 seconds, then put the battery in correctly again to reset it- you will have to reprogram the clock time and date and any settings you had previously.

I believe what your experiencing is the 75 degrees is the hold temp position...the display then reverts back to the actual room temperature...it doesn't mean the set temperature changed back to 65 degrees. Try to reprogram the thermostat schedules, and try not to use the hold function...just the temporary hold. (which is bumping the programmed temperature up or down until the next programmed period)

First change the batteries. If that does not help, perhaps the user manual will give some hint as to what this means. I hope this helps.

Without speaking with you live I can only suggest you call 1800 Honeywell they have excellent experts there to walk you through the setup of your stat, you could kill the power to the unit 1 hour and remove the stats batteries to reset to default but calling Honeywell will be a better easier experience.

HONEYWELL WEBSITE:
Go to honeywell.com
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions
If you can’t find what you want, the bottom left and bottom of web
Page, they have homeowners assistance and Home products to get the help you need.

you may vae to enter a different "Mode" to change the time....also try removing the batteries for 10 minutes and then reprogram the thermostat again

Most likely: You have to now "reprogram"your key fob and car to recognize each other. Look in your User's Manual for the car or, if it's an aftermarket fob/lock system, look in the user's manual for that. If there's nothing about battery replacement/reprogramming procedures, and it's a factory system, head into a dealer to reprogram it. It could run you up to $120, but that's cheaper than buying a new fob or system. If it's and aftermarket system and the manual says nothing, go to the place you had it installed (repair facility, Future Shop, etc) and have them reprogram it. If they installed it, they should know how to reprogram it.

Keep in mind, that's only the most likely option. Another possibility is that the receiver in the car, transmitter in the remote, or lock actuators/relays, etc in the car are the issue. It may not have been batteries in the first place at all. That said, it was most likely the batteries, and your best bet is trying to figure out how to reprogram the fob and car to recognize each other.

the cooling setting will not go below the heating setting. lower the heating setting so you can lower the cooling