Why does my new shower head just run cold water?

who connected the shower head

The only shower heads I've seen had the water mixed (hot and cold) before it ever got to the shower head, through one pipe. However, it could be a malfunctioning mixing valve. Partway down in this article is info about the shower valve: http://www.superterry.com/shower-hot-cold/

I hope this helps:

https://www.justanswer.com/plumbing/467sz-hot-water-not-coming-shower-head-however-hot.html

Believe it or not, the type of shower head you use can affect the temperature of your water making a huge difference in the amount of hot water you have available. Only two-thirds of the water heater’s capacity is usable hot water (a 50 gallon tank gives approx. 33 gallons.) If you have a shower head that is limited to 2.5 gallons per minute (GPM), you would have approximately 15-20 minutes until the temperature drops, but if you have 5GPM – you would only have 8-10 minutes of hot water.

Tests you can do:

Don’t use any hot water for at least 4 hours.

In a 5 gallon bucket with a 160 degree minimum temperature thermometer, turn the water on hot and allow it to fill the bucket. The thermometer should be in the stream of the hot water flowing out. Record how many times you fill the 5 gallon bucket before the temperature drops by 20 degrees.

To determine the GPM (Gallons per minute) rate of your shower head, hold a bucket up to the shower and have someone turn on the shower and fill the bucket for 30 seconds.

Determine how much water is in the bucket. Double that amount to get you GPM. If the bucket fills one third of the way in 30 seconds, consider switching your shower head to a low-flow shower head. This will not only stretch your hot water usage, but also conserve water.

Does the shower head have a flow-control valve located on it?...

weirdly no hot water comes out just cold I will try and find a low flow one as suggested and see if that works. this is just a shower directly from water tank somehow the hot water just does come through but does if I put the old one back . it's just a normal screw on head nothing fancy .