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Kimmy

Climate control turns off

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Any ideas why my climate control turns off and comes back on its own?  It does it for the ac and the heater. If I change the temp, the whole system shuts off and resets to the temp it was at before.  If I don't change the temp, it just shuts off and comes back on. No one around me knows where to start. 

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First place I always start looking, when I have intermittent failures, is loose or corroded connectors.  The resultant open circuit is like a switch opening and closing.  No popped circuit breakers or burnt fuses.

 

If you had a short circuit problem, you would get blown circuit protection, open circuit problems do not.

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Which model year are you having this problem with?

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12 hours ago, Mike Chell said:

....

If you had a short circuit problem, you would get blown circuit protection, open circuit problems do not.

I've noticed that on the wiring diagrams for a lot of the TC controls, much of the switching is done in the modules and the switching is done by completing a circuit to ground. Normally I am used to seeing switching done on the power supply side of a circuit and a short to ground does tend to trip the circuit protection. With this switching on the ground side of the circuit, I can see where a bad wire or other component intermittently shorting to ground could be interpreted by the modules as intentional control switch operation. And if the normal switch to ground doesn't trip the protection, then neither would a short to ground in the same area of the circuit.

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Just for clarification ... most computer controlled systems switch the ground side of the circuit.  Less voltage on that side of the load, easier on the "switch".

A ground after the load but before the switch (control) is labelled an "unwanted ground" ... not a "short to ground".

 

But you are correct ... an unwanted ground can cause a circuit to switch on intermittently.  However, that's not the situation here.  The circuit isn't "switching ON" intermittently ... it's "switching OFF" intermittently.  That has to be an open on either side of the load.

 

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Most of the New cars switch the ground.  One of the  first things to do on  any of these can bus vehicles is to do a scan, The body control Module  controls the AC. 

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Ground side switching is common in JDM vehicles.  It used to be that "American" autos were switched on the positive side.  This was also back in the day when "American" autos were not imported, and Honda & Toyota weren't produced in U.S.A. plants.  Back when an "American" car was SAE and not metric.

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Not sure if it’s changed but my 96 Taurus had full power flowing through the multifunction stalk switch so it burnt like a candle. I wonder if it was ridiculous engineering or Ford tried to save money by leaving out a relay for headlights.

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Ford saving money with bad engineering is not new. All the rest of the companies have done the same thing.

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I can recall off-road lights, 100W each & sold in pairs, used to be sold with an inline fuse, and a switch.  Battery to 20A fuse, to switch, to lamp.  The lamp grounded itself through the mounting hardware into your bumper.  No relay.  And everything was hot.  The wires got hot.  The switch got hot.  The lamp got hot.  That was just how things were when people drank Tang, wore polyester leisure suits, and Disco ruled.

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