So my car's engine decided it wanted to spin a bearing or bend a rod a couple of weeks ago and I was caught suddenly without a vehicle. With limited time and resources before returning to work I ended up buying a 1997 Blazer. I don't really know much about the history of it other than being told the rear brakes and ball joints needed work. After purchasing I also noticed the rear diff cover's pretty bad and leaking a bit and either oil or possibly the transmission may be leaking but I'm not sure which. The both the oil and transmission fluid levels look good and both look like they're in good shape. The engine was swapped at some point and apparently only has 156,000km on it or so. The underside has a fair bit of rust. The body has about 300k km on it.

First issue I've dealt with is some kind of parasitic drain on the battery I haven't been able to track it down to any of the fuses so I ended up buying a battery disconnect switch so it doesn't die over night until I can figure it out. I was getting around a 0.33mA drain with the engine off. It looks like a lot of the electrical system has been hacked around and random stuff is disconnected so it could be anything.

I had the brakes checked out and the rear brake shoes and mechanisms need to be replaced but the mechanic adjusted them and they've been working much better since for the time being. The abs light is on though and may or may not be related to the back brakes the front brakes were recently worked on according to the previous owner and there doesn't seem to be any leaks and the brake fluid looks fine.

Most recently I ran into a troubling transmission issue and the truck seemed to be stuck in second gear and wouldn't shift. The check engine light came on and I got a P0740 and some other tranny related codes. I ended up having to drive the truck like that for two days to and from work. It was not great. Luckily I did quite a bit of research on this forum and it seemed like the likely cause was actually the ignition switch. The key hadn't worked properly since I bought it and never fully went to the off position. I ended up ordering one in at the auto parts store and swapping it out today and I'm happy to say my transmission problems have so far disappeared and on top of that my turn signal lights are displaying properly on my gauges. Only the right one worked previously and that was intermittent.

I did find something a bit concerning. I'm not sure exactly what they've done down there but the small set of wires was disconnected and it looks like the wires they connected to was cut off and rerouted somewhere else. Then a bunch of wires were tapped into the big wires on the ignition switch harness

I didn't take any pictures while I was working on it but this is a picture of the wiring on the old switch I removed with the wire taps.


Old ignition switch

The yellow wire was cut and connected to a relay and I'm not sure where the other ones are connected. I ended up just replicating what they had before and connecting all the wires the same way. I have a feeling whatever they did is possibly responsible for the power drain. It looks like there may be some after market stereo equipment. It all seems to work but my power drain has gone up to 0.44mA so obviously something was messed up with the old switch because some circuit is now working that wasn't before.

I'm a little bit worried about tapping onto the ignition switch wires but I wasn't sure what else to do. I tried to make sure my solder joins were good and used connectors for the yellow wire going to the relay. I did notice the grey connector that slides into the ignition switch connector seemed a little burned. I'm not sure if that would be from their mickey mouse wiring job or not.

Thank you to all the people who posted about the ignition switch problem over the years and to the users who did both the anatomy of the ignition switch and the ignition switch replacement write ups. Other than the wiring hacks I found everything went smoothly thanks to all the info I found here. I never would have even thought the ignition switch could cause transmission errors and I was getting ready to drain the transmission and check the solenoids and I was not looking forward to that. It seems a bit crazy to have so many crucial components running through that little switch.

I'm hoping I can get the truck into a decent shape. I'm looking forward to having an offroad vehicle again and it seems like it could be a pretty nice truck for camping. The engine isn't the fastest but it seems to have some good torque and I have taken it down some small offroad runs and it definitely does well there. It came with a pretty decent lift and has great clearance. Feels a bit scary around corners but I'm starting to get used to it.

 

Welcome to the forum! And congrats on figuring out the transmission/ignition switch connection. That is new to me and I've been wrenching on my 99 since about 2009. Be sure to ask questions and feel free to share what you learn.