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 Post subject: AC relay wiring question
PostPosted: Mon Aug 15, 2016 9:56 pm 
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I'm chasing down an AC problem. System is fully charged (45lo/145hi) and works great, sometimes. Other times the compressor clutch doesn't engage. I tried switching the AC and viscous heater relays and it didn't help. (Dropped the relay into the engiine, but I guess I won't be needing the heater for a while.)

I want to try hotwiring the relay to see if the compressor comes on. I see 5 connectors - two kind of vertical and 3 kind of horizontal. They're marked 1,2,3,4 and 5.

Does anyone know which two I connect together to make the clutch engage?

Thanks.

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 Post subject: Re: AC relay wiring question
PostPosted: Mon Aug 15, 2016 11:34 pm 
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graycenphil wrote:
I'm chasing down an AC problem. System is fully charged (45lo/145hi) and works great, sometimes. Other times the compressor clutch doesn't engage. I tried switching the AC and viscous heater relays and it didn't help. (Dropped the relay into the engiine, but I guess I won't be needing the heater for a while.)

I want to try hotwiring the relay to see if the compressor comes on. I see 5 connectors - two kind of vertical and 3 kind of horizontal. They're marked 1,2,3,4 and 5.

Does anyone know which two I connect together to make the clutch engage?

Thanks.


Try looking up a Bosch relay diagram on google. The pins are not usually labelled 1-5 but 30, 85, 86, 87, and 87A so you will need to take a look at the diagram and figure out which is which. Also, they may be labelled 30, 85, 86, 87, and 87A on the relay itself.

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 Post subject: Re: AC relay wiring question
PostPosted: Tue Aug 16, 2016 6:11 am 
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The relay or the relay socket will have the markings.

You need to jumper pins 87 and 30 together inside the relay socket to supply power to the AC clutch...check with a voltmeter that +12 volts is in fact there or you could have a blown fuse somewhere.

Doing this over-rides the "Refrigerant Low" switch so if you run for too long with this jumper in place and refrigerant is low...you will destroy the compressor! :shock:

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 Post subject: Re: AC relay wiring question
PostPosted: Tue Aug 16, 2016 7:27 am 
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Thanks Billwill and Masshole. The only wiring diagrams I could find used the regular Bosch numbers. I did find this picture of the relay with a diagram on it, but am still not sure what the numbers mean.

http://www.rockauto.com/en/moreinfo.php ... 372&jpid=1

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 Post subject: Re: AC relay wiring question
PostPosted: Tue Aug 16, 2016 8:56 am 
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Okay, I figured out the pins. There is a diagram on the side of the relay with the Bosch numbers. It's the two vertical pins that you jumper to make the compressor run.

I jumped them, and the compressor ran fine and made cold air. So something isn't telling the relay to close.

I found the two sensors (thanks Geordi) the high pressure one on the AC line near the battery and the low presure one on top of the drier. I'm going to try jumping these (one at a time) and see if that makes the compressor run. Make sense?

Thanks again.

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 Post subject: Re: AC relay wiring question
PostPosted: Tue Aug 16, 2016 10:38 am 
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Okay, I jumped the low pressure sensor (the one on the drier) and the compressor comes on. Ordered a new sensor. I think it's the sensor because the system seems to be fully charged (lo45/high245 on the gauges).

Next question: When I unscrew the pressure sensor, will I lose R134?

Thanks again.

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 Post subject: Re: AC relay wiring question
PostPosted: Wed Aug 17, 2016 8:03 am 
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graycenphil wrote:
Okay, I jumped the low pressure sensor (the one on the drier) and the compressor comes on. Ordered a new sensor. I think it's the sensor because the system seems to be fully charged (lo45/high245 on the gauges).

Next question: When I unscrew the pressure sensor, will I lose R134?

Thanks again.


No...from posts I have seen the sensor can be removed without loss of R134! :wink:

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 Post subject: Re: AC relay wiring question
PostPosted: Wed Aug 17, 2016 9:04 am 
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Yeah the sensors are usually installed into a shrader valve. So you should be ok.


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 Post subject: Re: AC relay wiring question
PostPosted: Wed Aug 17, 2016 10:01 am 
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Thanks. Ordered the part from Rockauto.

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 Post subject: Re: AC relay wiring question
PostPosted: Tue Aug 23, 2016 6:43 am 
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Update: replaced the sensor and AC runs normally again. $9 part, and very easy to do. Thanks again to all.

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