OK obviously its no big deal if I lose my preset stations but if I disconnect the battery, Is there some anti theft deal that I need to know to get the radio to work again? I know many newer cars have this.

 

Probably.
Check the owner's manual. There's a procedure to turn off the lock out 'feature' (total PITA) that's easy to do. I'd print it but don't have access to the book just now. One of the first things I did upon purchasing my neighbor's used Blazer was to disable that 'feature'
Good luck.

 

I'm sure your blazer was equipped with the "theftlock" feature and if it hasn't already been turned off by the dealer it could cause issues when disconnecting the battery, and the dealers like to sock it to you just to disable or reset one that has been theftlocked. Best bet would be to check the owners manual and disable it first before disconnecting the battery and then leave it disabled when you're done just in case of future power failure.

 

That would be great but I don't have an owners manual. My daughter bought this second hand.
I will have to rig up some clips to the battery to keep power to the system. I need to pull teh battery Tray to 'f' around with this ridiculous 4WD system. Give me solid front axles any day

 

This is directly out of the '99 Blazer owner's manual.

Hope it helps.

Theft-Deterrent Feature (If Equipped)

THEFTLOCK

radio. It works by using a secret code to disable all radio

functions whenever battery power is removed.

The THEFTLOCK feature for the radio may be used or

ignored. If ignored, the system plays normally and the

radio is not protected by the feature. If THEFTLOCK is

activated, your radio will not operate if stolen.

When THEFTLOCK is activated, the radio will display

LOC to indicate a locked condition anytime battery

power has been interrupted. If your battery loses power

for any reason, you must unlock the radio with the secret

code before it will operate.

Activating the Theft

-Deterrent Feature

The instructions which follow explain how to enter your

secret code to activate the THEFTLOCK system. It is

recommended that you read through all nine steps

before starting the procedure.

NOTE: If you allow more than 15 seconds to elapse

between any steps, the radio automatically reverts to

time and you must start the procedure over at Step 4.

1. Write down any three or four

-digit number from

000 to 1999 and keep it in a safe place separate from

the vehicle.

2. Turn the ignition to ACCESSORY or RUN.

3. Turn the radio off.

4. Press the 1 and 4 buttons together. Hold them down

until

- shows on the display. Next you will use the

secret code number which you have written down.

5. Press MN and 000 will appear on the display.

6. Press MN again to make the last two digits agree

with your code.

7. Press HR to make the first one or two digits agree

with your code.

8. Press AM

-FM after you have confirmed that the

code matches the secret code you have written down.

The display will show REP to let you know that you

need to repeat Steps 5 through 7 to confirm your

secret code.

9. Press AM

-FM and this time the display will show

SEC to let you know that your radio is secure. The

LED indicator by the volume control will begin

flashing when the ignition is turned off.

Unlocking the Theft

-Deterrent Feature After a

Power Loss

Enter your secret code as follows; pause no more than

15 seconds between steps:

1. Turn the ignition on. LOC will appear on the display.

2. Press MN and 000 will appear on the display.

3. Press MN again to make the last two digits agree

with your code.

4. Press HR to make the first one or two digits agree

with your code.

5. Press AM

-FM after you have confirmed that the

code matches the secret code you have written down.

The display will show SEC, indicating the radio is

now operable and secure.

If you enter the wrong code eight times, INOP will

appear on the display. You will have to wait an hour

with the ignition on before you can try again. When you

try again, you will only have three chances to enter the

correct code before INOP appears.

If you lose or forget your code, contact your dealer.

Disabling the Theft

-Deterrent Feature

Enter your secret code as follows; pause no more than

15 seconds between steps:

1. Turn the ignition to ACCESSORY or RUN.

2. Turn the radio off.

3. Press the 1 and 4 buttons together. Hold them down

until SEC shows on the display.

4. Press MN and 000 will appear on the display.

5. Press MN again to make the last two digits agree

with your code.

6. Press HR to make the first one or two digits agree

with your code.

7. Press AM

-FM after you have confirmed that the

code matches the secret code you have written down.

The display will show

-, indicating that the radio is

no longer secured.

If the code entered is incorrect, SEC will appear on the

display. The radio will remain secured until the correct

code is entered.

When battery power is removed and later applied to a

secured radio, the radio won’t turn on and LOC will

appear on the display.

To unlock a secured radio, see “Unlocking the

Theft

-Deterrent Feature After a Power Loss� earlier in

this section

 

Register your VIN atGM Owner Centerand you can download a .pdf of your owner's manual.

 

Thanks All I got an owners manual. They talk more about Child car seats than Light bulb part numbers and Tire sizes.. weird.
Anyway. I read the whole Theft detterent thing that was nicely listed above by Megalodon_Al.

Notice it says nothing about how to turn it off if you DON'T know the code. There is no mention on some Display lamp indicator showing that it is Activated.

I took a shot, unplugged the battery and all was good. Whew.

 

I could never find my code... I have that delco theftlock. Thank god, I've never had any trouble with it locking itself