Wireless Network Issues

Currently, have a small network setup with about 20 computers on our Domain. We are currently using a Cisco RV220W wireless router. I'm having trouble keeping a consistent signal from being pickup for everyone to use. I believe it's because of the pipes and metal around the area are the root cause of the issue. I have an additional router of the same type that I could make into a AP, but every time I try to change the additional router into an AP, I have problems with the conversion. I've change the IP manually, I've disabled DHCP so it wouldn't interfere with main router. Yet still no dice. Can anyone give me ideas on how to address this issue. Thanks