The AP-175P calls for 802.3at power - I've seen 175's operate with af power, but the unit eventually would not boot. In addition to this, I trust you are using an outdoor rated POE injector such as the one we SKU (PD-9001GO) which contains the necessary surge protection for outdoor AP deployments. Indoor rated PoE injectors simply don't have the protection for outdoor usage although some people choose to use them. For outdoor deployments, we need to be mindful of both the issue of lighting and transient surges such as those that could be realized if the Cat5/6 cabling is run along side of electrical wiring.
You should be placing the PoE injector either outdoors (the the one above can be mounted with the AP) or at the building envelop where the cabling runs into the building. The use of STP (shielded twisted pair) is always recommended for outdoor deployments. Also, please ensure you've grounded the AP itself properly to the provided grounding point (specified in the AP-175 UG)
Let us know what brand/model of injector you are using. Attached is the one we recommend for outdoor deployments.