Low voltage through ignition switch

[koolaid_kid]

All those Bosche Type relays are relatively inexpensive mechanical relays. That means when it is activated the only resistance is that of the relay contacts or the external connections.

I dont want to go through all possible combinations of how it might be possibe to miswire the relay, but the single check you could do to confirm if the wireing is wrong is to do the following:

You can not have a voltage drop between pins 30 and 87 when the relay is activated(well maybe if you have a direct short to ground but you would see smoke then).

So if if Pin 30 was the (+)battery and pin 87 was +10.5V then your battery has to be +10.5V and it is not fully charged (assuming normal ignition loads you should be closer to 12.0V with ignition on and engine not running; +12.6-12.8 with the key off).

So if you measure the voltage difference between pin 87 and the Battery (+) (which drives pin 30) and you see any voltage drop (when it is activated) you have the relay wired wrong.

So with the key OFF you might see +12V between pin 30 and 87; but with key ON it should drop to zero. If not it is miswired.

http://www.mp3car.com/vbulletin/faq-...w-wire-up.html

Well, yes, although I would call it an electro-mechanical device. The coil inside the relay, when activated, turns the relay on. While it is true that the points inside the relay will wear with time, this is a new relay. The connections have all been soldered by me and are solid.
Pin 30 is the battery input, and measures +12.5V. Pin 86 is the switch point, and activates the relay. It measures 10.5V. Pin 87 (active ON) measures 0V. Pin 85, the ground, measures 0, or ground.
I have used my multimeter to check each point of the relay, and they are correct. Key off, I would expect to see +12V at 87a, which I don't use.
I'm not trying to be a smarta@@, trust me. I apreciate the input.

[posplayr]

Pin 30 is the battery input, and measures +12.5V. Pin 86 is the switch point, and activates the relay. It measures 10.5V. Pin 87 (active ON) measures 0V. Pin 85, the ground, measures 0, or ground.
I have used my multimeter to check each point of the relay, and they are correct. Key off, I would expect to see +12V at 87a, which I don't use.
I'm not trying to be a smarta@@, trust me. I apreciate the input.

OK so does Pin 87 go to +12V when activated or does it read something else?

[koolaid_kid]

OK so does Pin 87 go to +12V when activated or does it read something else?

Still 0 volts, unfortunately. Fundamental issue. To me, that means the relay is not activated. Perhaps I should also monitor 87a?

[posplayr]

Still 0 volts, unfortunately. Fundamental issue. To me, that means the relay is not activated. Perhaps I should also monitor 87a?

You are correct; it doesn't sound like it is activated.

Have you tried to run a separate ground to Pin 85?
Sounds like there might not be a ground.

[koolaid_kid]

The Final Solution

So, I tabled this for a while b/c it was clear to me that I was missing something fundamental.
Bwringer came over and checked it, and found two issues:
First, the terminal for 86 pulled out of the socket. He reinserted it and we both heard it click into place. He was unable to get a voltage reading even after that, so he tugged on my connection, and the pigtail wire pulled right out of my connection. We reconnected it, and heard a satisfying "click" when the key was switched on. Everything is good now.
"It worked on my bench" is my only lame excuse. Thanks to everyone for your suggestions, I greatly appreciate it.