Trying to install new batery and the minute I put the second cable to battery the horn starts going off How do I stop this. I thought I disconected the horn but it keeps going off

Sounds like a anti theft. Put your key in the ignition but not in the start. just put it in. See if you can remove the battery now without the horn going off. If you can also find the horn and un hook it. there should be a connection clip if you trace the wire down.

Hope that helps
Dan

check security system if aftermarket disconect it

Try this:
SAVE radio code and remove the negative battery cable,turn on the headlight switch for 30 seconds,turn back off,start truck.
That MAY re set the alarm relay.

My first thought would be the horn relay is sticking.
Or a short in the horn pad on the steering wheel.

There are a few things that can cause the horn to stop working. First thing to check is to use a 12volt probe light and take the wire off the horn, put the probe between batery ground and the horn wire now have somone push the horn switch, if the probe lights then change the horn. If no light then chech the horn fuse. If the fuse is good then maybe the switch. Pop off the center of the stearing wheel and mak sure the switch is clean and shinny if so you are now looking for a broken or disconected wire. Good Luck

disconect both batery cables and touch them together for 3 seconds waite a few minuts and connect batery back up. and see what that does

First of all I would go to like Checkers, or Auto zone and let them put a battery draw down tester on your battery and check the battery.Second I would check your battery connections if the batter checks out. Also check engine grounds. You will hear noises when re-powering up. That is normal.

lock the car using the key to reset the alarm

Check the voltage drop on the battery cables, they may be defective.

plz check the following and update me
1. Fuel (To be exact proper air/fuel ratio, normally it is about 14/1)
2. Spark (in appropriate moment)
3. Proper timing (the valves should open and close only in appropriate time)
4. Compression in the cylinders (Normal compression is 120 - 170 psi. The engine won't start if the compression is lower than 70 - 80 psi.)