High speed mode of Cooling Fan

Hello again!

My 99 Transport 3.4 does not want to run the "high Speed" mode of it's cooling fan. I have hooked up a scan tool - and tried to force the high speed mode of the fan but can only activate the low speed setting.
The guage needle is climbing around the 100 mark - should be at the first mark and staying there! If I drive it - the temp comes down...

Any thoughts???

Thanks in advance,

Shane

Hey Shane,

There are three (3) relays involved for the fans, but one is "special" for high speed mode. I have some details about the system at the link below, including a schematic. That should help some.

Cooling Fans (http://www.my-chevy-venture.com/engine-cooling-system.html)

Take Care,

Thanks very much! I will work with this and let you know how I make out.

Thanks for the help. I tested all of the relays and fuses - even checked all wires - still nothing. It appears that the engine also stalls the second the high speed fans try to kick in. There are no codes being tripped - just a stall. Once the engine cools - it will start right up again...

any other thoughts?? I am thinking computer but it is expensive and once you buy it you can't return it..

again - thanks!