1993 Explorer Runs Without The Key
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1993 Explorer Runs Without The Key
Here's a good one. My 1993 Explorer continues to run when I remove the key from the ignition when I have the electric fan turned on but only when the temp probe is sending a "fan go on" signal. When I shut off the manual switch, the engine stops.
While it continues to run, all the various inputs/outputs to the PCM are active - readable on my scanner. But the voltage reading goes down to battery voltage - with the key on, the alternator voltage (higher) is displayed.
The only attachment between the electric fan (after maket) and the PCM is the "AC on, fan go on" wire. So the only thing I can think of is that somehow the signal from the fan's controller is connecting the power from the fan switch to back feed the AC signal line, go through the AC compressor circuit and power up the PCM. Shutting off the fan's manual swith then powers off the PCM.
Comments welcome as this is a wierd one.
While it continues to run, all the various inputs/outputs to the PCM are active - readable on my scanner. But the voltage reading goes down to battery voltage - with the key on, the alternator voltage (higher) is displayed.
The only attachment between the electric fan (after maket) and the PCM is the "AC on, fan go on" wire. So the only thing I can think of is that somehow the signal from the fan's controller is connecting the power from the fan switch to back feed the AC signal line, go through the AC compressor circuit and power up the PCM. Shutting off the fan's manual swith then powers off the PCM.
Comments welcome as this is a wierd one.
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Joined: Dec 2001
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From: UT
The main connection I could see would be through the AC WOT relay. The EEC relay supplies power to the entire engine management system via the red wire. One of those components powered by the red wire is the AC WOT relay. I don't know how you're fan is wired in. If it were using the coil side of the ACWOT relay, I could see it inadvertently bypassing the EEC relay to supply power to the entire engine management system.
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From: Winnipeg, Mb. Canada
Cool, now you can leave your truck running when it's -30 out and you just want to run into the ATM.
I would think since the pcm is recognizing that the ac is on because you are using it as a power source for the fan, maybe it's getting fooled into thinking the engine should be running? Any other power source you can use?
I would think since the pcm is recognizing that the ac is on because you are using it as a power source for the fan, maybe it's getting fooled into thinking the engine should be running? Any other power source you can use?
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Originally Posted by Backin72
Cool, now you can leave your truck running when it's -30 out and you just want to run into the ATM.
I would think since the pcm is recognizing that the ac is on because you are using it as a power source for the fan, maybe it's getting fooled into thinking the engine should be running? Any other power source you can use?
I would think since the pcm is recognizing that the ac is on because you are using it as a power source for the fan, maybe it's getting fooled into thinking the engine should be running? Any other power source you can use?
I think Mrshorty's explanation makes sense. The fan is not being powered by the AC clutch circuit. It taps into that line as a signal only. The little PCB board on the fan then triggers a relay that the main power is wired and fused to.
So 3 things can turn the fan on. 1) when the AC clutch is on. 2) when the temp sensor tells it to go on. and 3) when I flip the manual toggle switch.
Now I'll have to go back and read the directions again. Where I hooked up the manual switch, it said something about needing to order thier special toggle switch if you wanted to a switch to turn off the fan, disable it under all other circumstances.. I guess they have a 3 way switch - on/off/auto. I just used a regular togle switch and when I tested it, the fan went on. That's all I cared about so that's how I left it. Maybe I need their special one.
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Originally Posted by jecp
When did the problem develop? Sounds to me that something is wired wrong, or the control moduel is damaged.
The strange thing is it only does this when it is hot, hot enough to have the temp sensor tell the fan to go on. So it's tied into the auto run part of the circuit. It is adjustable, the temp sensor range, so I'll play with that to test that theory.
First I'm going to pick-up a new DPFE as I convinced myself that is bad. For 187K miles, it had a good life.
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