I managed to get this working on my test server. This is my document tree:
Products [11]
-Item 1 [13]
-Item 2 [14]
-Item 3 [15]
Product search [12]
Items 1-3 are my product pages, these are set to be published. They have the following TVs assigned:
[*model*]
Input Type: DropDown List Menu
Input Option Values: ||xyz123||xyz456||xyz789 etc.
[*partNo*]
Input Type: Text
[*prod-year*]
Input Type: DropDown List Menu
Input Option Values: ||2000||2001||2002 etc.
The first option in the list is set to be blank and I changed [*year*] to [*prod-year*] because [*year*] conflicted with something.
Product search contains the tvExplorer call and the document is set to be
uncached.
[[tvExplorer? &dittoName=`Ditto` &dittoSnippetParameters=`tpl:resultsTpl|parents:11|depth:0|display:all|sortBy:pagetitle|sortDir:ASC|showPublishedOnly:0` &formTPL=`searchTpl`]]
[+tve.searchForm+][+tve.dittoList+]
The Ditto parents parameter is set as 11 because this is the parent document of my product pages.
The resultsTpl is:
<h4><a href="[~[+id+]~]">[+title+]</a></h4>
<p>[+partNo+] - [+model+] - [+prod-year+]</p>
The searchTpl is:
<form action= "[~[*id*]~]" method= "get" >
<table width="200" border="0" cellspacing="0" cellpadding="0">
<tr><td colspan="2"></td></tr>
<tr>
<td class="searchFeild"><b>Make / Model:</b></td>
<td class="searchFeild">[+tve.model:filter->9:label->:tvtype->select:blankLabel->- Please choose -+]</td>
</tr>
<tr>
<td class="searchFeild"><b>Year:</b></td>
<td class="searchFeild">[+tve.prod-year:filter->9:label->:tvtype->select:blankLabel->- Please choose -+]</td>
</tr>
<tr>
<td class="searchFeild"><b>Part Number:</b></td>
<td class="searchFeild">[+tve.partNo:fullText->true:filter->7:includeTVs->partNo:label->:tvtype->text+]</td>
</tr>
<td> </td>
<td><input type="submit" name="search" value="Search" /></td>
</tr>
</table>
</form>
For the Part number form field I used fullText->true to allow partial string matches.
Try replacing your code with my examples remembering to change parents:11 to the ID of your parent document. Change the name of the [*year*] TV and make sure that the product pages are published and the search page is uncached.