I had an old battery that was failing so I replaced it. Now my power seats and power door locks don’t work. The breakers in the fuse box were very hot and I pulled them. I must have a short. Where do I start? 1986 C4 convertible

 

At the battery of course! FIRST be sure that you hooked the polarity up correctly or you will toast several major components of your C4. Then clean both Lead posts on your new battery.
You need to pull your fuses and start at the battery. Make sure that your battery supplies voltage to the Fuse panel as that would indicate that your fusible links are still okay and functional. Trying to find the particular circuit might be harder so I would get a harbor freight fuse ammeter and start checking each circuit. You can use a multimeter in the current measuring mode but the tool from Harbor freight is easier to use and cost $15. Here is the device I am referring to at harbor freight: I apologize for the size of the picture...


This little device will read how many amps are passing through the fuse. They make a 20 amp and a 30 amp version. Go through each fuse till you find the current draw that you are looking for. The normal parasitic draw is between 25 and 30 Ma for a lot of C4's. Check to be sure that you do not have any dead short using a multi-meter first before hooking up your battery.

Do not leave the battery connected if you suspect a major short/drain in your electrical system. Have a fire extinguisher handy while working on your Corvette until you get this power mess sorted out. Identify which breaker it was that got hot and check the circuit carefully. The seat motors have limit switches that fail and all sorts of things can draw substantial power and they work through the breakers.

Do you have a Factory Service manual for your particular year of Corvette? If Not you need to get one, they have a second book of nothing but the electrical parts of the car and has the schematics as well. very important to have in some form. The manuals are not cheap but are available on DVD for a lot less than the manual set.

Best regards,
Chris

 

The breaker is #20 in the fuse block - 2d from the bottom front. Sounds dumb, but did you happen to get something stuck in the console well pressing against the power seat switch? I used one of the HF meters to track down the draw on mine when I had problems. Assuming that's not your issue, start with the breaker out and look for grounds between the fuse block and battery.

 

My power seats and door locks also don't work and it is a 30 amp breaker in the fuse block. I had to pull it because it kept tripping and resetting and was getting hot. That fuse only runs power to those two items. Someone here suggested I pull the center console off and look for a grounded wire that runs to the power seat switches. Both things worked when I bought the car (91 L98). I haven't taken the console apart yet, so I can't confirm that that is the problem.

 

The seat tracks on the power seats can chew up the wiring harness on the floor under the seat base. That is always a good place to start! The console and parts are not hard to take apart so go for it looking for some wire associated with Power Seats or Power Locks. If you are nervous about damaging anything why you are working on the car you can put a fuse in between the battery and the car to protect your systems from too much current. It is another fail safe way to protect your car while tinkering looking for the short. When I had my console apart I found that my lateral acceleration sensor was swinging on it's wiring harness and not giving the car good signals.

Another really useful tool now would be a "Power Probe" as it would allow you to test connections and components very quickly. It is a handheld device that has a graphic display on it. When you touch the tip to an item it will tell you the voltage or if it is grounded. If you want to the rocker switch on the handle will turn the tip either +12 Vdc or 0 Vdc. This makes testing components very easy and finding shorts is not hard either.

Best regards,
Chris