My Interstate battery died as expected after 3 years. This time I went for an Optima Red Top AGM design rather than the old acid lead plate type that died even though it was on a battery tender all of its life with the hope this one will last longer. They send you a PUCK, which is the new hold down that is needed because the bottom section is curved in the Optima and this car was designed with a flat bottom surface to clamp down onto. My car was without a battery in it for a week until the new one arrived from Optima. I went with the manufacturer not Amazon or ebay because the battery's manufacturing date is newer and because the brick and mortar stores typically throw out this puck thinking it is packaging. Here is where my problem began. My C5 fired up and when I turned on the AC the interior fan was not running. The AC compressor kicked in but no air was being blown out the registers. I check all the fuses and relays in the engine compartment and all of them are fine. Evidently losing power for a week interfered with the many computers in the car. My electronic shop manual has a section saying the car needs 40 start cycles to relearn what the computers have to have stored for systems to function properly. I will take the car for a ride with the top down so I don't cook from the heat and lack of air circulation I used the onboard readout to pull stored codes and got 30 BCM codes, 2 SDM codes, 3 LDCM codes, 3 RDCM & 4 BO-RFA codes and NO HVAC codes. This is what I dread most about owning a high tech corvette with too many computers that are there to **** up. Why should replacing a battery cause all hell to break loose? This sounds like a reboot is the answer but why would disconnecting the battery solve the problem when disconnecting the of having the battery created the problem? Technology is wonderful when it works but is SUCKS when the computers cause a failure when the hardware is like new. I want my 1969 427 couple back because this nonsense would never happen. Does anyone have a crystal ball or know how to exercise the gremlin out of my car? It may just correct itself with driving.

 

You might just want to disconnect the negative battery cable for ten minutes or so and reconnect, it's worked for me on occasion.

 

Sorry to hear you're having problems with the AC...the 40 start cycles has to with any stored DTC's that may have set...if an issue say with your AC doesn't return after 40 "warm up cycles" that history code will be cleared from PCM's memory...the PCM isn't really relearning anything. Now these C5 are not very high tech...if you've come from a 60's musclecar to a C5 then yes it will seem complicated to you but these C5 systems are pretty antiquated...try working on a late model BMW with 60 or so computer modules and I'll show you complicated...LOL !!... OK, so the AC compressor is engaging but no blower fan...is your AC manual or automatic on your '99 ??...with the manual power goes from a fuse to a relay and then through a processor and then to the blower motor...the auto systems don't have this relay if memory serves me correctly...if you have a 12 volt test light that would help to diagnose this but I don't know what your skill level is at...you said you have the manuals so this should help…did you only visually check the fuses ??...best to check with a test light and also you will need one to check the blower motor and blower relay circuits to see why the fan isn't working.

 

Clear all the codes thru the DIC and see what comes back after driving a bit. When a battery fails these cars set a ton of codes

 

A ton of codes is an understatement! The old column lock failure message popped up even though I installed 15 years ago to correct the problem. The fuel gauge went to empty with a full tank with a low fuel level warning. This nonsense is enough to make me want to sell this car because this is BULLSHIT!

 

When your battery gets weak or dies it will throw a bunch of codes…just erase them all !!