The problem started happening a few weeks ago. I'd be driving and the engine and most of the electrical would quit. I could fiddle with the key and it would start up again

When this happens, the headlights and door and dome lights still work. I thought the ignition switch was the culprit so I took it apart, cleaned it with a brass brush but the problem persists and now fiddling with the key doesn't work anymore.

Batt voltage is 12.75 volts. Cables are clean and tight. I checked, cleaned and tightened the ground cable at the strut tower and at the large bolt on the starter. Also checked the positive cable at the alternator and starter.

Using the FSM and a digital ohm meter, I checked continuity in all positions of the ignition switch and they are what the FSM says they should be.

WHen I turn the key from ACC to ON, I hear a couple relays under the hood click and then when I turn to start, a relay clicks off under the hood and nothing. Also with the key in the ON position, the temp gauge moves up a bit but no other gauges or lights do anything and there is no power to the windows or climate control.

Here is something else weird. When the key is on, hitting the window switch will make the same relay under the hood click off just like when I turn the key to start.

The relay is the one next to the brake booster. I have taken the cover off it and tried holding the contacts together but it makes no difference. Still no start or gauges or power windows.

Could something in the CPU or alarm system be causing these symptoms? I don't know what to check next.

 

Have you tried jump starting it? Sounds like a low or sour battery to me, possibly your alternator isn't working correctly.

 

The battery voltage is about 12.75 volts checked with a Fluke meter and yes, I did still try jumping off my Suburban. I also hooked up an extra ground wire from the engine to the firewall.

The problem is not the common not starting issue. I have already searched and read through a bunch of those threads here.

 

Have you checked all the fuses? No offense, it just wasn't mentioned before.

 

Yup.

 

It's like a short, loose ground or bad relay but I can't find it.

 

if voltage is 12.75 with the engine running at the battery, thats low, it should be 13.5-14 ish

with the engine off 12.75 is good though.

next step is to look in the FSM. figure out what doesnt work, and then follow each path toward its source, where they meet, is where you should start looking.

for example, if the warning light cluster does not work, but the dome lights do, you can look at the FSM/wiring diagram and see that the power for the dome light and warning lights come from the same place, and are both grounded by the door switches (thats how the door open light works).

so if the door open light does not work, but the dome lights do, you know the door switches are good, the fuse is good because it gets power, etc etc the fault has to be in the warning light cluster.

the diagram is tricky cause you have to flip pages, but you can flip pages or randomly start checking stuff

 

Yeah it's 12.75v with engine off.

I'm going out there to start hunting again. Damn I hate electrical!

 

look at it logically. the hardest part is that the FC actually has a ton of stuff going on

 

Well, that problem is fixed. It was the ignition switch after all. I was taking the switch apart again and it was still connected and when I popped one side loose it began turning over. Turns out I had two of the springs in their incorrect holes. 3 springs hold up the 2 brass plates and are the same size but one of them is slighty different color than the other 2 and has less tension than the other 2. I put them back in the right place and it's back to good.