Corrosive Correction: C5 Battery Box Fix

The current-box on our C5 was eating our car alive!

By Andrew Bolig

Photography: Andy Bolig

When we talk about battery problems, we almost automatically conjure up images of slow-cranking engines or the disheartening view of all the indicator lights going from dim to dark the instant you try to start the car. Granted, batteries can be stealthy saboteurs, operating perfectly until they hit us with the silent treatment. Determined not to communicate with the starter anymore and equally resolved to pay no attention to the alternator, they make a show of force (usually at the most inconvenient time) that they are totally independent of the rest of the vehicle. This obvious defection from the team immediately warrants a replacement with another battery that's all too happy for the opportunity. Sometimes, though, we aren't lucky enough to have a blatant battery insurrection.

While at the Corvette Clinic, a '98 came in with what seemed to be an HVAC problem. There was no control of defrost, heat, or vent positions inside the car. The Clinic did some diagnostic sleuthing and found that the system did not have a supply of vacuum to operate the valves. What do the vacuum system and electrical system have in common on a C5? Follow along and we'll show you.



1. This was our first clue that bad things were on the horizon. The battery side terminals were leaking acid. You can see how the battery acid was running down the frame of the car, all too ready to claim its next victim. Our first step was to wash the area thoroughly with baking soda and water to neutralize the acid.



2. The main wiring harness is directly under the battery, as is the PCM. The acid was eating through the harness and, since the vacuum lines run as part of the harness, they were affected as well.

3. This is what is left of our C5's vacuum line for the HVAC system. A 2-foot section of the line was affected. If this line hadn't been affected, the acid would have kept eating away at the wires or followed the wires down to the PCM. That could have been really expensive.

4. We continued to cut open the harness to be sure the wires weren't affected. The black specks around the wires are all that's left of our vacuum line.

5. (above & right) The vacuum line for the HVAC goes under the battery area next to the firewall to a vacuum canister. We disconnected the line from the canister to check for any other issues.

6. We used a stretch of 1/8-inch hose to replace the original line. Don't use 5/32-inch because you can have a leak or the hose could pull out. Also, never use silicone to help slide the hoses together. It could wind up in the oxygen sensor.







Corrosive Correction: C5 Battery Box Fix (cont.)


7. After cleaning all the wires and checking for proper operation of the HVAC system, we rewrapped the harness with tape.

8. Before we installed the new battery, we laid down this Battery Mat. It's available online at It's chemically engineered to absorb any stray acid that might exit the battery. Even if you don't have a problem with your C5's battery now, for the price of this item, it's well worth having one around!