I had the glove box off my '89 4runner today and I saw a knob on what i think was the heater core, I know it wasnt the blower fan since thats down by the floor. Anyways it had H and L on it, high and low, I was just wondering what it is for?

And one other question, I changed my gauge cluster lights too and I bought blue ones at Oreilly and they arent very bright, I remember seeing a website online that specialized in colored automotive lights, but I cant find it, anyone know where I could get some good lights? thanks

 

if it's about the size of the palm of your hand, it might be the A/C Amplifier. If it is, the knob would be to control the A/C operation, turning the knob would basically change at what temp the a/c cycles off, turn the knob too far and the evaporator will freeze into a block of ice and you get no cold air until it melts

 

I toyed with mine on my 91 a while back when recharging my AC.

Seemed to me it controlled at what RPM the AC would cut off...

When my idle-up valve wasn't working, I could turn the knob all the way down and it would almost stall out the truck, lol.