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i have a dryer that has a 4 prong cord and the wall outlet was a 3 prong. I replaced the wall outlet with a 4 prong and the dryer works but will not heat did I wire it wrong or what could be the problem,

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    Good on you for fitting a 4-prong outlet, they are much safer. Now, did you have 4 wires in the wall? If not, which wire did you leave disconnected?
    – Harper - Reinstate Monica
    Jan 20, 2019 at 20:54
  • I had 3 wires in the wall red, black, white no ground wire. I hooked the wires up but without a wire for the ground prong
    – user95927
    Jan 20, 2019 at 21:04
  • Red X. Black Y and White W, I do not have a wire on the ground
    – user95927
    Jan 20, 2019 at 21:32
  • Can you post a photo of the inside of the box the outlet is mounted into?
    – ThreePhaseEel
    Jan 20, 2019 at 21:52
  • I do not have a photo and it is installed in the wall already. the only prong that doesn't have a wire is the ground prong, Because the old house, dryer outlet was a 3 prong outlet with only 3 wires .Black, red and white, no ground and it is a plastic box, so cannot add ground wire. My dryer is a 4 prong cord, so I installed a 4 prong outlet in the wall and the ground is the only prong without a wire. I am trying to find out why the electric dryer will not heat. It works but that is it, The clothes will not dry. Any ideas
    – user95927
    Jan 20, 2019 at 22:08

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It's two separate problems, based on your description.

One leg of "hot" not connected

Now I must admit, I leapt to the assumption that you replaced a large 3-prong NEMA 10 socket with a 4-prong NEMA 14, and that the previous socket was wired correctly (as correctly as a NEMA 10 can be).

The "dryer spins, no heat" symptom indicates that neutral is connected (to something), the right one of the two hots is connected, but the other hot is not connected. So I would carefully check the wiring connections at the socket. Also if your are able, check that there is 120V between each hot and neutral.

Now, there is one other place for this to go wrong, but it has nothing to do with installing a dryer. Sometimes a very clever person replaces the wide 2-pole dryer breaker that takes 2 spaces, with a "double-stuff" breaker that takes one space. That doesn't work, it will test out 120V on each hot lead, but they are the same pole, not opposing, so 0V between them instead of 240V. They need a quadplex.

The missing ground

Moving to a NEMA 14 style connector is a leap forward for safety, because the old NEMA 10 came with officially approved instructions to bootleg ground from neutral. The problem with bootlegging is, if anything went wrong with the neutral wire, It would definitely, positively, electrify the chassis of the dryer.

As you have wired this, that won't happen. However, if the dryer develops a certain type of ground fault, that can electrify the chassis of the dryer. Which is why we want to see a real ground there.

Usually people say "oh, noes, that means running a new cable from the panel"... Actually, no. You can retrofit just a ground wire. And you don't need to go back to the service panel, any of these will suffice:

  • a large appliance or junction box that has #10 AWG or larger ground wire going back to the panel
  • any junction box connected with non-flexible metal conduit back to the panel
  • anywhere along the grounding electrode system, the bare metal wires going from your main panel to your ground pipes or rods
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