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Old 09-07-2021, 06:07 AM   #1
haromaster87
 
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Default A/C electrical issue after alternator upgrade

Hey everyone,

I don't know how yet, but I screwed something up recently in my A/C wiring during my alternator/wiring upgrade. I had my 97 2.4l hardbody parked in the garage for about a week while I did everything, AC worked well and blew cold prior to me pulling it in. I installed a 110a Quest alternator, a 4 gauge cable from the ground junction to the frame, and replaced the main alternator-to-battery cable with a 4 gauge cable as well.

Today I found that I can turn on the AC switch and it lights up, but no engagement on the compressor. If I pull the relay and jump 3 and 4(to simulate the relay closing), AC fully kicks on and engine RPM increases.

I have the PDF of the service manual for the 97, so I found the AC troubleshooting and went down the list. I got fairly far down the list before I found anything that looked out of place. On page HA-39, they refer to the 4-pin connector for the Thermal Control Amp and to check pin number 4. When I accessed my TCA connector, it did not have a wire in the #4 spot and the connector on the actual TCA only had 3 prongs. Because of this, I was not able to do test K and L.

When I skipped forward, the next text was testing continuity from pin 21 on the ECM harness to a wire on the high/low pressure switch. I could not get any continuity to show between pin 21 and either wire on the pressure switch connector. Bypassing(jumping) the pressure switch does not engage the AC, but if I had a wire break, that would make sense.

Was wondering if anyone had experience with these two anomalies I ran into? It seems possible I have an issue with the wire coming off pin 21, but I don't want to trust that too much since my wiring didn't quite line up with the FSM.

Thanks for any help or advice!

-Tony
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Old 09-07-2021, 06:41 AM   #2
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I meant to add, I looked through old AC threads and this user had the closest issue to mine, but it seems he had a normal 4-pin connector and continuity on pin 21.

http://www.infamousnissan.com/forum/...ad.php?t=35290

I do have the option of a make shift 12v switch as a fix, but I'm hoping to track down the root cause.
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Old 09-07-2021, 06:47 PM   #3
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Well, scratch this I think. Turns out I was too stupid to test the actual high/low pressure switch and I was unplugging some other two pin device mounted on a hard line just below where the actual pressure switch is. I jumped the pressure switch connector and everything turned on, so I will continue down that path.
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Old 09-08-2021, 10:43 PM   #4
cadillacdude1975
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The refrigerant is either under/over filled or the switch is faulty.
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Old 09-09-2021, 04:16 PM   #5
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Quote:
Originally Posted by cadillacdude1975 View Post
The refrigerant is either under/over filled or the switch is faulty.
Yeah I'm wearing a bright orange dunce cap on this one. I was so convinced the issue HAD to be electrical, because of my recent changes, that I never bothered to hook up the AC gauges and find that the pressure was way down. I must have developed a leak while it was sitting.

On the plus side, I know the electrical side of the AC system almost back to front now lol.
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Old 09-10-2021, 05:14 AM   #6
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Probably needs orings. You can replace all of them in an afternoon.
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Old 09-12-2021, 01:43 PM   #7
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I've got a '98 and a 2004 Frontier in Arizona. The only refrigerant leak I have had was a pinhole in the high pressure line of my '98.


I think you - or a real AC shop - should add some refrigerant and UV dye to the system and then check for leaks.


NEVER ADD ANY SEALER OR REFRIGERANT CONTAINING SEALER TO AN AC SYSTEM !!! Note capitals and bold !!!!
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