I recently bought a 99 blazer. It started out the security system locked the vehicle from starting. Fixed that. Then 2 days later the lights on the dash started to flicker and it started pulling codes. Cadillac converter code for one. It seems fine when it isn't raining and the vehicle is dry. The problems seem to start after it gets moist. Any suggestions?

 

Electrical issues for sure All the lights on the dash as in ABS Engine light Or Normal running lights ? Reason i ask is I once had ALL the lights flashing on and off Airbag ABS Engine light and Batt come on and off and then the whole car shut down Seemed my ALT gave up and died in a rain storm on my 2000 Cavailier I would check the last thing that was fixed on the truck maybe a loose wire or bad ground. See if the ECM is wet or the connection is tight (and yes i have had water come in to the cabin ) I ran a Amp wire in a hole with another GM wire and forgot to put back the rubber gormet back around on the passager side foot well and after a rainy day going back the bottom of the carpet was soaked .....Check / Clean /tight grounds (free) check ECM also free When you start the truck your volts should not have a big drop and would regain back up near 14 I'm going to assume you have a CS130 Alt how long have you had it? if it came with the truck its time to change it Try running everything you can when running High beams, Radio, Heat/A/C Wipers 4-ways Foot on Brake De icer and horn See if any of your problems return and how far the Volts gauge drops If you get the issues back ether have the Alt Tested or replace it ..I changed mine a few months ago From a CS-130 to a AD-244 bigger more power Alt that runs things like Power seats and extra usage (car computer, extra lights etc) but you need also to change to a bigger belt If you just want it to do the same job stick with the CS-130 You can buy them New Rebuilt and Used (auto yard ) Hope it helps