RV Repair: Wiring Suburban NT-12SE, vw vanagon, starter solenoid

Question
I bought a VW Vanagon with a Suburban NT-12SE furnace.  I'm changing the aux battery to a GEL cell and changing out the relay (that seperates the two batteries, typical starter solenoid type) for a Yandina 100 combiner.
My question is how to wire the furnace, the power is straight forward, but the thermostat relay wiring has me confused.  The relay I have has five spades, the center one is not used.  Two opposite spades go to the thermostat (blue wires), one spade is for power (red wire), and the remaining spade was attached to the small terminal of the solenoid with a yellow wire.  What is the function of the yellow wire?  (I don' have a wiring drawing or operator's manual). And how should it be wired?  Thanks

Answer
The function of the yellow wire is a ground wire. I believe on that particular model furnace there are 3 connections with 4 wires going into them. The red and one blue wire are tied together, then there is another blue wire and then the yellow wire. The red and yellow go to the main power side (Red) is hot and (Yellow) is ground. The 2 blue wires make no difference how they are hooked to the T-Stat because their only function is to complete the circuit and are regulated by the T-Stat. If there is anything more I can help you with feel free to ask.