When checking for short circuits, make sure everything is powered off.
Will do! Thanks again
Quick test, I’m out at soccer now but I had a few minutes before I left the house. With the pcm orange plug unhooked and the battery unhooked, no continuity between db/pk and any ground I try.
Suggest to start by using a 12 volt test light to probe relay junction box between 85 and 86 (with relay removed) under a condition where the fan would be running when it shouldn’t be (like with battery connected, engine cold, and key in “on” but engine not running). That will tell you if there’s an actual problem with the 85/86 input to the relay or not. Don’t do that measurement with a volt meter b/c a volt meter doesn’t draw enough current to get an accurate reading. You’d have to have the relay installed and still have access to the pins to get an accurate measurement with a volt meter. But a test light draws enough current by itself.
The reason for that, if you are wondering, is b/c the PCM uses a solid state switch to either connect 85 to ground, or it leave it unconnected to anything. But b/c of the way a solid state switch works, the unconnected state might measure the same as connected if you use a digital volt meter.
Thanks, actually I was curious. Electronics drive me crazy. I won’t get to try it until Sunday, I’m leaving after work tomorrow for the weekend. I’ll post back as soon as I get home Sunday evening/night and let you know how it goes.
Bat +… DVM +
Bat -… Switch … DVM -
With the switch “on” you’d measure battery voltage accurately.
But with the switch “off” the measurement would be meaningless. Voltage is always relative, the difference in potential between two conductors. When the switch is “off” there’s only one conductor connected to anything. If you don’t know if the switch is on or off, what do you do? Use a test light instead
Bat + … Test light +
Bat - … switch … Test light -
If the switch is “on”, the light will light. If the switch is “off”, it won’t. the test light provides an indication of both current and voltage.
Finally back on this, I really appreciate the explanations too. Ignition off, test light connected to + battery and probing 85/86 gives me a light on 86 but not 85. Also no light between 85/86. When I probe 86 connected to battery it trips the auto shutdown relay with key off. Key on I get no light on any of the tests connected to battery + or between 85/86. If connected to battery - probing 86 gives a light as does 87.