It is an industry standard that electrical parts are often NOT RETURNABLE! These parts may be calibrated and can easily be damaged, by mishandling or improper installation, without showing any physical signs.
Items that are acceptable for return for credit will often be subject to a restocking charge of 15% to 50%. This is to help defray the cost of time involved and of parts listings needed to look-up the proper part for your machine.
Items (including electrical components) that fail to function within the given warranty period for that part should be replaced (not refunded) by the supplier without a restocking fee.
On-line merchants may require you to apply for a return authorization before they will accept returned goods.
Any items not stocked by the parts depot will usually require a deposit before ordering. This deposit can be anywhere from 50%-100% of the item value.
Specially ordered items are usually NOT RETURNABLE unless a mistake is made by the parts supplier or the manufacturer. It is your responsibility to ensure that the part ordered is the part that is at fault!
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Before ordering anything, be sure to ask or read the terms of sale the particular merchant adheres to.