Battery Disconnect Switch, was 2000 Blazer Going Off


2000 S-10 Blazer, 121k miles with new battery installed on 10/20/11. After a near lightning strike in July the alarm has been going off during rainy weather. I was hoping the new battery would help but the alarm went off at 6:30 am this morning after a day and a 1/2 off rain. The original thread is below.

If anybody knows how to disable the Theft-Deterrent system that would be great. Otherwise can anybody recommend a good quality battery cut-off switch for a side terminal battery? I am also going to disconnect and clean as many connectors to the ECM and BCM that I can get at. Any suggestions for an anti-corrosion spray I can use on the connectors or will dielectric grease suffice?

Would a knife blade battery disconnect switch be a good choice? It would be the easiest to install.

Thanks in advance,

Ed B.

Try locking the doors with the key, not the keyfob. I can’t imagine that GM would have been so stupid as to disable the alarm when you locked it with the remote.

For battery cutoff, try the Battery Brain. They even have a remote control version, but the remote part doesn’t always work very well.

I don’t think cleaning the connectors is going to do you any good. It sounds to me like the lightning was close enough to zorch your electrical system. While the locks were only disabled temporarily by the residual charge, it sounds like the alarm’s circuit board was damaged.

If you disconnect the battery you will lose the memories on things like the ECU. If you have to do an IM test at some point you will not be able to pass the test due to the monitors not being set.

I think you would be wise to invest in a factory service manual for the wiring to help you locate things and then disconnect the sensors for the alarm system except for one of them as a test to see if that may be where the problem is at. Then keep adding another one as the sensor circuit checks out. There may also be a high resistance fault on one of the sensor leads that is changing resistance with the moisture in the air and you could possibly find it using a ohmmeter checking the resistance to ground. The service manual will pay for itself with just this one repair job.

Thanks for the suggestions.

Shadowfax, I went back and reread the Owner’s Manual and it appears the only way to disable the system is to manually lock the door. I stand corrected. I drove the Blazer to work after leaving the battery disconnected for ~30-40 minutes. The truck ran fine, but the door lock switch was still not working. I disconnected the battery at work and let it sit for a few hours. After that the door locks worked normally.

Cougar, thanks for the suggestions on how to troubleshoot the problem. I never bothered with a service manual for the Blazer since I have a good mechanic and the truck is not easy to work on. Now I have a good reason to pick up one.

I installed the disconnect switch described in the link and that should hold me for now.

Ed B.

Shadow said exactly what I was going to tell you to do…lock it with the actual key…thats a biggie

Just an update on the Blazer. The alternator started to make a loud whining noise on Saturday. It turned out the battery disconnect switch did not have a good connection. Once the switch was removed from the negative terminal the alternator quieted down. Hopefully it hasn’t been fried.

For now, I’ll use the key to lock the door to disable the alarm. There’s rain expected later in the week, hopefully the alarm won’t go off.

Ed B.

The alarm has a fuse somewhere…Remove it…

I wish it was as simple as pulling a fuse. However, there is a horn only fuse I could pull in a pinch.

Ed B.

Fuses usually supply power to more than one thing so it may not be the practical or temporary solution.