aux. fan - 300TD

My auxilary fan was not working in my '81 300TD so I tested it by disconnecting it and running a hot lead to the battery while grounding the other lead. The fan did not work. So I purchased a used fan off
ebay and tested it the same way. It worked, so I installed it. I wanted to test it again and heard that if I pull the wire from the temperature switch, which is located near the thermostat, and ground the wire, the fan should run. I tryed, but nothing happened. I did see a little spark when I grounded the wire. I checked the fuse in the fuse box located on the firewall but the fuse was good. Am I doing something wrong? Is there an inline fuse somewhere? How can I check to see if the fan is working properly?
Thanks, Gary
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The engine does NOT control the aux fan on a 123 body. ONLY the A/C works the fan. Go to the drier behind the right headlamp. See the tiny switch mounted to the top? Bridge those 2 wires with the key on and the fan should run.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I believe there's a relay that's activated by the temperature sensor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So when is the fan suppose to come on? When the engine temp reaches a certain temp or when the AC is on?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Engine temp will NEVER turn it on. It ONLY comes on when the AC temp is too high. The ONLY temp sensor for the fan is in the top of the AC drier.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.