For ReSound Quattro’s, the receiver wire is an integral part of the receiver. I seem to recall that a special tool is required/recommended to detach the receiver wire (and receiver) from the body of the hearing aid. If anyone has recommendations on where to get the tool or what to use in its stead, I’d be happy to hear them. But swapping receivers on HA bodies, if you have the tools to do it, would be a good way of distinguishing body circuitry failure vs. receiver failure as tenkan suggested above.
On testing receiver performance, I’ve found that I can do a crude job by playing tones from an Android tone generator app into over-the-hear headphones one ear at a time vs. streaming the same tones one ear at a time to my HA’s. Since both receivers are unlikely to fail to the same degree in both ears at the same time, one ear serves as a “control” or reference point for the other ear, which you may perceive to be doing worse, etc.
If you’re into DIY, you can always use in-situ audiometry as a built-in test of how your receivers (and HA circuitry) is performing. If you’ve had a recent audiogram and your HA’s have been appropriately programmed for that audiogram, the in-situ audiometry audiogram should relatively closely reflect your audiogram done by conventional means - that tests amplification of low-level sound into a range that your hearing can just detect. If you use the in-situ audiometry feature for evaluating the discomfort level of maximum volume sound, that can very grossly test whether your receivers are still capable of producing output so loud it’s uncomfortable. I have moderate-to-severe age-related high frequency hearing loss, both ears are about the same, and sound frequencies across entire range that HA’s typically address is more or less “recoverable.” Such a strategy is obviously not going to work very well for more complicated or much more severe hearing loss and obviously if you can’t play around with DIY, the in-situ audiometry will not be an option. But the tone generator tests initially suggested might at least give you an idea how well or badly your HA’s are currently performing and if you have an essential job, e.g., nurse in an ICU, maybe you could find an audiologist or HCP somewhere in recognition of your dedication to society who would service your HA’s if you can’t figure out and fix your HA’s yourself.