advanced search fields seem to be linked

I have an auto auction where I want to be able to search by price, make etc. Currently you cannot search by one or the other. Ex. I have a list of makes, followed by a list of prices. There is an auction for a Chevrolet Malibu with a price of $2200. If I leave the make blank and search for the price,$2200, I get no auctions found. If I search for Chevrolet I get the correct auction. If I search for Chevrolet and price of $2200 I get the correct auction.If I search for Chevrolet and a different price I get no auctions found, which is correct. This makes me believe the custom fields are somehow linked.
Is there a way to have the custom fields searchable independently?
You can see the site at
https://www.autoauctionsofne.com/wordpress
Thank you
Kevin