Batteries were dead. put 2 new 12 volt batteries and hooked them up the way the old ones come out + to+ and - to - I turn the switch on and have no lights, no horn , motor won't run. fuses are all good. I put charger on it to test output and it showed 24 volts, but nothing works on it. Is there anything else I can check on it. Thanks, Bob

You need a volt meter the problem is some ware between the battery and the ignition switch .Check battery grounds all if bat is grounded you should have 6.5 v D.C from B+ to anything on the engine or frame one at a time then test both for 13 v at the same time jump them together .This could be your problem 2 battery's with 1 bad ground .Then start from the other end the ignition switch use jumper leads hook to the switch in start position key turned to black to ground see what you have for voltage drop it should be around 12 volts if you have nothing its the ignition switch if you have less then 12 v its likely a bad ground from one of the battery's or something related to the drive motor

Hooking up 2 batteries (IN SERIES) will give you 24 volts. First make sure the 2 batteries are exactly the same. Do not use mismatched batteries. Hook the POSITIVE of first battery to the NEGATIVE of the second battery. Then hook your LEADS ( hot and ground) to the 2 remaining posts. That will give you 24 volts. When charging the batteries with a charger, hook the charger up to the LEAD POSTS.

12+12=24

You are right to suspect the battery if the weather is hot and the battery is a few years old. You probably have a dead cell and that will prevent you from jump-starting it.
It takes at least 10.5 volts to engage the starter.
You could disconnect the battery and charge it overnight then check the voltage, but I would lean toward a dead battery from old age and heat.
Make sure the connections on the posts are clean before you take the battery out. Could be some hidden corrosion.

When its hooked up, you should be able to put 12 volts on the little stud on the solenoid and it should start. One large stud will have 12 volts on it, so just jump it right there. Did you get the wires in the right place. The solenoid should have 1 large wire going down to the starter. Be sure the battery cables are clean and tight ( both ends) Check battery voltage when cranking, should go to 10-11 volts. Check voltage between negative terminal on battery and engine, should be ZERO when cranking. The solenoid has 2 large studs, make sure the battery positive wire and all the other wires are hooked to this stud, the other large stud should just have the wire going to the starter.

Remove the old battery and clean the cables and battery posts. Hook a battery charger to it and fully charge the battery. If it will not hold a charge or the problem continues, replace the battery as it has shorted or dead cell. After replacing the battery or if the battery appears good and then runs down suspect the alternator is bad. Check the voltage at the battery with the engine running. You should have at least 13.5 volts on a 12 volt system and 7.5 volts on a 6 volt system.

do you have power to the solenoid?? with the key on there should be 12 volts on one side of the solenoid then when you turn the key to start it should send 12 volts out the other side to the starter

short or loose connection

A 12 volt battery is actually 13.2 volts fully charged. If you are reading 16 volts, you are probably getting extranious voltage from the system somewhere, especially if the vehicle is running when you check the voltage. The alternator will put out about 15-18 volts to charge the battery normally, and yours may put out 28-32 volts to charge them in series, but the batteries, when disconnected, should never read more than about 13.2 volts each. Typically, it will read about 12 1/2 volts when disconnected. COMPLETELY DISCONNECT BOTH OF THE BATTERIES. If you still read 16 volts when it is disconnected, you must have a bad meter because the battery can't produce that much voltage, no matter what. (Six 2.2 volt cells connected in series inside the case.) Put the meter on a known good battery on another car that is not running and see if you get the same reading. It sounds like the other battery is almost dead, regardless, and it sounds like your series/parallel switch may be malfunctioning. (That is the switch that puts the battery in series to run the 24 volt starter, then puts the batteries in parallel to run the remainder of the vehicle on 12 volts. This is all assuming that you have a diesel vehicle with a 24 volt starter and that is why you have two batteries.