Hi everyone!! its been so long since i've posted but i have a problem, and since hubs has a lot of stuff on his plate right now i figured i'd put it to the pros to see if you guys could help me fix it myself.

we live in south-eastern georgia, and it is sweltering here right now. problem is, whenever i go to turn on my A/C, my transmission temp light comes on. it ususally goes off within 5 minutes of me turning off the air, but once or twice it would go off, then turn on and off randomly for about 10 minutes. not flashing exactly, it was slower than that. we had to pull a friend out of some sand last night, and the light came on and off the whole time we were working on pulling him out. i put it in 4-low and drove it around the yard a bit, tryin to get the light to come back on and once i got it on, i temped the transmission (187*) and the transfer case (exhaust side 310*, opposite side 290*). hubs got an infra-red thermometer, so thats what i used to temp it.

my problem is, i obviously want to use my A/C, especially since here at Ft Stewart its going to stay in the between 80 and 90 for the next month or 2. but i want to try and do it myself. help me!! please!!

 

Radiator also has the tranny cooler (gearbox oil cooler) mounted at the lower front of the radiator, so you may be just about overheating. so:

1. Check coolant level. Check tranny fluid level. Check oil level in transfer case - will need to open fill port with a wrench. Your IR temp readings seemed kinda high, but might be from very heavy use.
2. Check viscous drive clutch for main radiator fan ENGINE OFF - should be stiff when cold, not spin more than just a part of a turn. When warmed up, should not spin more than half a turn, certainly not free wheel (tech sticky has write up on $49 Chevy subsitute). [this is the #1 suspect after low coolant and/or low fluids].
3. When cold and cranked up, fan should move enough air to "roar", this goes away in 2 minutes or so. Poor fan clutch performance shows up when moving slowly, not at highway speed. You don't need a fan when driving, but you need it when stopped or very slow. Sand hogging is certainly high power, low speed, so would need fan in tip top shape.
4. Cupped side of blades goes toward motor. No blades missing.
5. My previous owner reworked the wires to the AC condenser fan on the front "little radiator" and got them reversed, when my AC was on, I always overheated at idle, because it was blowing out the front of the vehicle. Easy to test with a wimpy plastic bag held in front of the grill, should suck toward grille, not blow away.
6. Belt route? Discover Discovery Maintenance Tips, Accessories, Parts & More at Roverparts.com
7. Radiator, space between radiator and AC condenser (the little radiator in front), and condenser itself clogged with leaves, mud, etc. DO NOT CLEAN WITH PRESSURE WASHER.
8. If radiator needs boil out service, Gary's in Statesboro is a good and low priced indy shop. $65 to flush out and rod out and solder up my D1 (all brass and copper). D2 is different. You can also try commercial flush from parts store at home.
9. Water pump? Not so cheap. Thermostat - cheap. But these would normally show up at times besides AC on.
10. Rock of the Marne!!
11. One D2 at LKQ salvage yard in Garden City (no water pump), Cash & Carry just crushed the 4 Discos they had.


From the tech manual:

 

On the stuff to fix list;

seat don't move - $22 - $27 at salvage yard, or take cable loose from motor and operate with electric drill to get to position you can live with.

knock on accel - be sure to use premium gas

autoparts stores will usually read codes for free - report back

 

Forgot to mention, the front electric condesner cooling fan is controlled by the ECM, based on a number of heat factors. But when you are running AC in Hinesville after lunch (hot days) it should be running at certain times. If it never runs, problem. On older D1s it ran whenever AC was on, but D2s are "smarter" (more complex) than D1s.

 

So how many miles on this truck, when did it have it's last service especially the tranny, when did you last check your tranny fluid, do you know how to? Might want to check the t/case fluid, it is connected to the temp light also.