73 deville issues

My grandpas got this big boat, and he's having a few problems with it. When you turn on the the heat, (or move the slider from off), the fuse blows. We've tried unplugging things such as the a/c compressor and random plugs, but could not figure out the problem. We also replaced the whole switch unit, and has not solved the problem. We went through about 23 fuses trying to solve this. Does anyone have an idea what it could be?

And another issue that could be related

The battery randomly dies. He has been through 3 new batteries and none would hold a charge. Obviously something is shorting out but we cannot figure what. The alternator and starter were replaced, but it did not make a difference. When the battery is charged, the car runs great. but when you turn it off, wait a few hours (time varys, can even take days) the battery will be completely dead. Any suggestions?

Thanks

Not sure about the '73 but most Caddies have a blower control module located near the blower motor on the firewall. Try unplugging that and see if fuses still blow or the battery goes dead.

already tried that unfortunately. no difference

My grandpas got this big boat, and he's having a few problems with it. When you turn on the the heat, (or move the slider from off), the fuse blows. We've tried unplugging things such as the a/c compressor and random plugs, but could not figure out the problem. We also replaced the whole switch unit, and has not solved the problem. We went through about 23 fuses trying to solve this. Does anyone have an idea what it could be?

And another issue that could be related

The battery randomly dies. He has been through 3 new batteries and none would hold a charge. Obviously something is shorting out but we cannot figure what. The alternator and starter were replaced, but it did not make a difference. When the battery is charged, the car runs great. but when you turn it off, wait a few hours (time varys, can even take days) the battery will be completely dead. Any suggestions?

Thanks
2 things here get a wiring diagram and see exactly which components are in that fuse circuit and start tracking things down, no magic here basic diagnostics. 2cnd, get an ammeter in line with the battery cable and see if there is a draw with everything shut off.

thanks alot for that last reply. i just recieved a wiring diagram yesterday and i am going to start looking over stuff. And for that last part about the ammeter, i have never thought of that! lol. I will be sure to do that. thanks

well. my grandpa went out and bought a 95 caddilac sedan deville yesterday. v8, 4.9L. i just fell in love with the thing. Talk about great acceleration and speed =) Anyways. He's decided he's going to sell his 73 because of too many issues.

well. my grandpa went out and bought a 95 caddilac sedan deville yesterday. v8, 4.9L. i just fell in love with the thing. Talk about great acceleration and speed =)

Great acceleration and speed from a 4.9! hehe, they are quick, but you better not let grandpa drive a Northstar powered car! :) I had a '94 Deville with a Northstar, and it was a rocket!
Your grandpa should keep the '73 and fix it at his leisure.

whats Northstar? never heard of it lol. As for the 73. Were having too many issues with it. Its got no climate control, so u cant use defrost or a/c or anything. We still couldnt find the problem. And because of its age, we found a lot of rust underneath the material on the roof. And theres some rust on the quarter panels. His wife says one is enough, since they pass everything but a gas station hehe. Plus he's also got a 91 mercedes benz which he is probably also getting rid of. Were going to try and find a good owner for the 73 caddy tho. it needs some tlc. hopefully we can find someone who will buy it and restore it.