My '87 300 TDT blows cold air for about 3 minutes and after that just fan blowing warm air... It has plenty of refrigerant and does not feel like it is overheating. Help!

Tell us how you know it has the correct amount of refrigerant ?

registering 230 on the high side and about 35 on the low side....

What are your controls set at ... have you tried them maxed out.. except low for the blower ?
What refrigerant ?
Which compressor ?

Do you know which AC type system you have ... like type 2 or type 3 ?

Those readings are at high idle.. with a fan blowing into the radiator ?

low idle and the fan probably not blowing too hard because the fan clutch is not too good...

Are you referring to the Fan Clutch on the engine ?
These tests are supposed to be at high idle and with proper air flow... otherwise you get the high pressure or high temp switch cutting your cooling to protect the compressor...
Just a possibility...
also, do you have a pencil thermometer to stick into the vent while you test ?

thanks for your help so far- I will take another good look tomorrow to get some more details.

OK, Goodnight and Goodluck.

I'm guessing type III

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I always hope they have the type I... for selfish reasons...

It's the best one to have.......

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John