Most e-stim problems come down to the contact or the leads, not the unit. This article lists the common symptoms and what to check, starting with the most likely cause.

Before any check: turn the level to zero and switch off. Never go looking for a fault with the output turned up.

Nothing happens#

  1. Is the level actually up? Many units won't start unless the level was at zero when switched on, and some lock the controls after a short time.
  2. Batteries. Fit fresh ones, the right way round. A unit can light up and still be too flat to give a proper output.
  3. Both electrodes on? You need two contacts on the body for each channel. One on its own does nothing.
  4. Right channel? Check the lead is in the socket for the control you're turning.
  5. Plugs pushed fully home? A jack plug that's a millimetre out doesn't connect.
  6. Electrodes touching each other? The current takes the shortcut.
  7. The lead. Try another one. Broken leads are the most common fault of all. See Cables and Connectors.
  8. The electrodes. Old pads and tired conductive rubber stop conducting. Try a fresh pair of pads.

Sharp stinging or a hot spot#

This is poor contact, and it's the symptom that leads to burns. Stop at once.

  • Pad edge lifted, or a pad that no longer sticks: re-seat or replace it.
  • Dried gel: clean off and re-apply. See Conductive Gel and Lubricant.
  • Hair under the pad holding it off the skin.
  • Too small an electrode for the level: turn down or use a larger one.
  • Broken or irritated skin under the electrode: move elsewhere.
  • Lotion or oil on the skin: wash and dry it.

Contact Area and Current Density explains what's going on.

Sudden jolts or cutting in and out#

Almost always a connection that's making and breaking.

  • A broken wire inside the lead, usually right at the plug or pin. Flex the lead gently at a low level and see whether the sensation comes and goes. Replace it if so.
  • A loose plug, pin or adapter. Each adapter is another joint.
  • An electrode that moves as you do, losing and regaining contact.
  • Weak batteries.

Stop using a lead that does this. The jolts when contact returns are unpleasant at best.

One electrode feels much stronger#

  • It's the smaller one. The smaller contact always feels stronger.
  • Its contact is worse: less gel or a lifted edge.
  • The unit's pulses aren't balanced, so one side of the channel naturally feels stronger. Swap the two wires over. If the strong side moves with the wire, that's the cause.

The sensation fades#

  • Your nerves have adapted. This is normal with steady pulses. Change the mode or pulse rate instead of turning up.
  • Gel is drying. Turn down and re-apply.
  • Batteries are fading.

The unit switches itself off#

  • Session timer. Many units stop after a set time. Check the manual.
  • Open-circuit protection. Some units cut the output when they detect an electrode has come off. Find the bad contact.
  • Low battery.

Muscles cramp or lock up#

The level is too high for that pulse rate, or the electrodes are over a muscle that's contracting hard. Turn down, slow the pulse rate, or move the electrodes. Cramp that doesn't ease when the level drops means stop for the day.

Skin is red afterwards#

Even pinkness under the whole electrode that fades within half an hour is common. Small red dots, a red outline, soreness or a blister is a burn. Leave the area alone until it has healed, and work out which of the causes above was responsible. See E-Stim Safety for when to get medical help.

When it really is the unit#

Suspect the unit if a fresh battery, a known-good lead and new pads still give no output on one channel, the output is erratic on every lead, a control does nothing, or the case is hot, cracked or has been wet.

Don't keep using a unit that behaves unpredictably, and don't open it up unless you have the training to work on it. Contact the maker, or replace it.