Thermal Control Amp. Bypass question - Nissan Xterra Forum
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#1 Old 09-14-2011, 07:58 AM
ybfly
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Thermal Control Amp. Bypass question

I have an 02 X. The AC compressor clicks on and off randomly (mostly off). The cooler it is outside the more the compressor stays on. I checked the system pressure and it is good indicating that I do not have a leak. I jumpered the magnetic clutch on the compressor to keep it on and the air is ice cold. From what I have read from other posts, I might have a bad thermal control amplifier. I ordered the part last night ($38 out the door online). I then tried to bypass the thermal control amp so I would have cold air while I wait for the new part to come in. I know, bad idea. The thermal control amp has three wires (red, black, white). I put the red and white together and the compressor kicked on for a second then I accidently contacted the black connection. I got a spark and compressor went off. I restored the TCA to the original configuration but now my AC light on the switch will not come on. Apparrently, I shorted something out. I checked all fuses and relays. Everything is good. Any ideas on what I might have messed up? Also, when I was testing relays, I noticed my fog lights do not work (not sure if is related or not). When I get home tonight I will use a multimeter to check all the fuse connections. Anything else I should check?

I am new. This is my first post. You guys seem great and I will appreciate any input. Thank you!
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#2 Old 09-14-2011, 09:36 AM
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sounds like you have it covered with your plan. fog light fuse is a 10 amp iirc in the under hood fuse box. not sure which fuse or where it would be.located for the TCA... most likely the interior fuse box as most switched fuses are located there (switched as in circuits that are on/off with the key)

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#3 Old 09-14-2011, 10:38 AM
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DOuble check the one on the fuse panel under the hood It should be a a 7.5A fuse and is the only one linked to the TCA in the service manual. It appears to be a sort of ignition on line so that would explain why the fogs don't work either.

Last edited by miskywhisky; 09-14-2011 at 10:40 AM.
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#4 Old 09-14-2011, 04:34 PM
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I checked the fuses under the hood. They are all good however, no power is going to one of the 7.5A fuse block. I show 12+ Volts on all the other fuse block connections. I am not sure what to check next. Any ideas?
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#5 Old 09-14-2011, 05:16 PM
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I am going to disconnect the battery and pull the fuse block to try and trace the wires to the 7.5A fuse. Ill post my findings. If only I had a wiring diagram that I could read.
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#6 Old 09-14-2011, 06:13 PM
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No good. The wires do not have enough play in them to get a look. However, I started the X up and checked the fuse block and I got around 14 Volts on both terminals of the fuse. So I am guessing it is either only powered when the key is on or its being back fed somehow. I hoping the former. I am not sure but I think the wires going to the TCA connection come from the A/C switch. I unplugged the TCA and checked the voltage from the ground pin (middle) to one of the other two with the A/C switch on and I got 0.02 Volts. When I turn the switch off, it goes to 0 volts. Could I have blown the A/C switch? I turned the key off and checked continuity with the same two wires. Switch off, I get nothing. Switch on, I get a reading in the mega ohms. To me it seems there is some slight connection there. I'm thinking my next step is to pull the A/C switch. Its dark now so Ill try tomorrow. I could use some help. Am I moving down the right path or should I be checking something else. Thanks for your input so far.
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#7 Old 09-14-2011, 06:57 PM
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It looks like the circuit board got damaged. you can see in the photo where its disconnected. Ill try a repair but I will probably end up buying a new board. Let this be a lesson, don't try to bypass something in less you know what you are doing. I welcome all comments. Thanks for reading.
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#8 Old 09-15-2011, 06:23 PM
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Well... I soldered the circuit board and IT WORKED!! I am impressed with myself. Never soldered anything before. It's ugly but it works. The A/C kicked ON because it's cooler out and it's ice cold. Still waiting for the new TCA. I'll update and let you all know if the TCA was truly the problem after it has been installed a few days. This a great forum and I am learning a lot from all the other posts. Thanks to all.
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#9 Old 09-27-2011, 03:14 PM
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I installed the new TCA a few days ago and that seemed to fix the problem.
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#10 Old 06-16-2014, 10:13 AM
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OH WOW! I just did the same exact thing... I shorted the wires together trying to bypass this TCA. Now I guess I'll try and find the panel that you are talking about. And see if I can solder it as well.

I guess I crossed the wrong 2 wires first trying to bypass the TCA.
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