See the attachment for your wiring diagram.
Unplug the unit and both wires at the heater.
Measure the heater should be 8 to 12 ohms.
Then check from each side of the element to the heater's case.
Both should be infinite ohms.
If not the element is grounded and could run hot.
Did the unit have good air flow?
Check that the blower wheel is properly connected to the motor armature.
Sometimes they strip out. Will spin some but not enough.
Check that the blower wheel is clean.
If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.
There is a good STICKY at the start of this forum about it's use.
