Low volume output from radio. appears to transmit and receive properly

If you're close enough to hear the receive on one radio while transmitting on the other, it's good old-fashioned feedback. Turn the volume down on the receiving radio.

use + side of the volume toggle button on the side of the unit

Without more in depth detail you have had your receive damaged by a high power radio transmitting near you. I suspect a blown diode or tr7 the first RF amp transistor has failed.
Now it you are describing a low volume problem. Like the volume of your radio not increasing when you plug it in that can be a broken with in mic cord, bad switch in handset or solder connection at mic plug. It will still transmit.

? I assume you are asking if you need an ariel antenna for this radio in order to receive and transmit? if that is the case then yes you do, Any radio requires a matched antenna in order to transmit, if you were to transmit without an antenna, most of the RF energy will transfer back into the radio and over heat "burn out" the output transistors. always make sure to have a proper antenna connected before transmitting on any radio.

On the radio with the low volume, it is possible you are having a low receive (Rx) issue, or you have a bad volume potentiometer. It would need to be seen by a radio technician to determine the exact cause and if it can be repaired. In most cases, the flat rate repair for this style of radio is around $69 ea.

Your second radio with the transmit button (PTT) issue likely has a failing push-to-talk internal button, or a broken spacer behind the rubber plug. These would be common failure parts on this type of radio and replaced during a repair.

Best regards.

Did swapping the batteries produce normal volume from the previously low volume radio?

It does seem like it is a battery problem. These days no household should be without a decent battery tester...

The problem could be with the mic. If there is a problem with the mic it will make either the receive not work, or the volume seem real low. The weather will work fine if the mic is bad.

adjust the hi and low power on side band ,also make sure you have good SWR match.

It sound like a bad reostat in the volume control. if its under warranty send unit back to kenwood and have them replace the volume control, and possible speaker involvement.

Hello..if you can try to connect a external speaker or phones..if the volume is ok..than i think it is time to replace your internal speaker..pse tll me....good luck...Ron