Dear jd620,

Hope you're well and stay so. I've not had this problem. I've also not had occasion to disassemble a side-mounted mirror. I thus rely on parts diagrams and on-line photo. See, or example: https://www.volvopartswebstore.com/products/Volvo/Mirror-glass--right-Genuine-Classic-Part/1177173/9447757.html

Those photos show the mirror has "ears", that fit into recesses in the mounting. If those "ears" have broken-off the mirror, then you can either replace the mirror glass (Volvo #944757) or try to adhere the mirror to the mounting.

Because the mounting and the mirror's rear surface are plastic, it is not easy to find an adhesive, that bond chemically with the plastic and so provide a lasting bond.

One adhesive, that may work, is butyl rubber. This black or grey material is very sticky. If applied to a metal, glass, or plastic substrate that has been cleaned of all dirt, grease, etc., butyl rubber will not only stick, but it will remain flexible for years. That's why butyl rubber (or caulk) is used to adhere windshields to metal bodywork. The butyl rubber seals the opening because it adheres strongly.

As the mirror - like a windshield - is subject to wind buffeting (vibration), having a durably flexible adhesive means the micro-movements will not cause bond failure.

Most auto glass shops have butyl rubber tape - flat or round - on hand. You'll need only enough to go over the circumference of the mounting area.

Clean the mounting areas - on the mirror body and the mirror glass - with acetone (or methy ethyl ketone, if you can find it) - to remove any contaminants. Press the butyl onto the mounting in the mirror body. Then, align the mirror carefully and press it onto the butyl rubber.

This should create a strong and lasting bond.

Hope this helps.

Yours faithfully,

Spook