light

if i put a light in the middle of the cage will it work for both the sides?

What do you hope to accomplish with the light? What animal do you have in your enclosure?

Is the light your heat source?

Cause if that is the case, that is woefully inadequate.

like my Warm side is fine, my cold side is at 70. it wont go up i put foil to insolate it, i have a light but it gets to hot and only have one dimmer

You will probably get a lot of feedback on this. I had a similar problem. I ended up putting in a second UTH with it's own thermostat control and digital thermometer probe for a hot & cool side. Now all is grand in my BP's life.
Good luck.

does the zoo med 500r work for both temps?

I have ZooMed thermostat, and a Zilla Thermostat on my two UTH's. The Zilla works a lot better, with a 2-3 degree swing while turning on & off. I notice the ZooMed side can swing about 8 degrees. I am purchasing another Zilla to replace my ZooMed this weekend. From reading a TON of these threads the advice that is issued is that the thermostat is one of the most important items to splurge on, and the online stores have a great selection. But no, the ZooMed will only run one side, not both with different temperatures.