Wiring A/C help

[chief_shotts]

I am in the process of getting my A/C fixed up and ready to go. For context I'm working with an 1987 r30 engine bay that has been molested up and down by myself primarily. In all my infinite wisdom 5 years ago at 20 years old I stripped out any "unnecessary" wiring. swapped in a 383 stroker and added a holley sniper. Since then I have replaced All the A/c components in hopes to one day get it running on r134a. That includes adding a fancy sanden 508 compressor.

Most of the heater/AC wiring remains and is operational. The wiring that is missing is the +12v wiring from the dark green wire coming off the low pressure switch to the A/C compressor. My first question is: is it true that there should be a diode close to the compressor on this 12v wire to protect the electrical system from the compressor when it cycles off?

My plan for rewiring the A/C compressor was to add a relay that is triggered by the dark green +12 volt signal wire coming off the LPCO switch to power the A/C compressor? Additionally I want to wire up my A/C compressor to the Holley sniper, specifically to the Holley sniper A/C IAC kickdown input, so that the sniper can compensate for the load of the compressor cycling on and off. The Sniper A/C IAC kickdown input requires a -ground signal so i will need to wire up an additional relay that is triggered when the A/C is powered on and sends a ground signal to the Sniper. I'm going to attach a drawing of these relays and how i think they should be set up and maybe someone can tell me if it looks good or if it needs to be changed.

 

[chief_shotts]

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[edgephoto]

The clamping diode is used to stop voltage spikes when the clutch is disengaged. That spike can take out electronics. It would induce a high voltage when the coil field collapses, like an ignition coil works the diode stops that from happening.

 

[chief_shotts]

Updated my wiring idea. I also found a relay that has two common 87 outputs so I'll be using that to trigger both the ac compressor wire and the ac kickdown relay. Amazon should be delivering supplies shortly... trial by fire... hopefully not electrical fire tho.

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[Ricko1966]

Updated my wiring idea. I also found a relay that has two common 87 outputs so I'll be using that to trigger both the ac compressor wire and the ac kickdown relay. Amazon should be delivering supplies shortly... trial by fire... hopefully not electrical fire tho.

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Terminal numbers on this new relay?. You aren't confusing a relay with 87 and 87a as dual output are you. Because those are 87 is hot or 87a is hot. Not both at the same time

 

[chief_shotts]

terminas

Terminal numbers on this new relay?. You aren't confusing a relay with 87 and 87a as dual output are you. Because those are 87 is hot or 87a is hot. Not both at the same time

This relay I'm talking about has two 87 outputs. Bosch 0 332 019 155

 

[chief_shotts]

Update for anyone this may help. Here is verified wiring diagram for the relay harness I put together to power my AC system. LPCO green wire triggers the first relay and sends power to a/c compressor. Second relay is a normally closed relay and when activated by the sniper (-) output at a given TPS value it will open the relay and shut the a/c off. The third and final relay sends a signal to the sniper that the ac is running allowing the system to adjust the idle air control to compensate for the extra load at idle. Ignore the trinary switch.. i didn't use that. System works good so far

The diagram is curtesy of a member over on the holley forums.

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[Broken85]

Here is the actual wiring instructions from Holley for the Sniper 2

 

[edgephoto]

Why do you need the first relay? The Dk Grn wire is what energizes the coil normally.

 

[noelsautomotive]

Did you end up not using the diode? Relays result in same protection?

I did an LS swap into dads 1987 R30 and ran the green wire directly to the compressor, but the HVAC switches don’t seem to be working right and the compressor cycles off/on ever 3-5 seconds…reading your post, I’m wondering if I fried something.

 

[YakkoWarner]

I am curious about the diode mentioned a few postings back. Where would that diode be in the wiring? When I got my truck the connector for the compressor was missing, but the wires were still there. I put individual spade plugs on the wires and connected them to the corresponding spade pins on the compressor (R4 type only 2 wires). It runs/cycles (and doesn't run when the system is low so seems correct), but if there is supposed to be a diode in there protecting the other electronic elements I absolutely want to install it. The A/C is kind of inop at the moment (compressor runs, pressures seem OK on the gauges but not much in the way of cool air comes out) so I'm not using it, but I would really like to get it working.

 

[Sad Sack]

I am curious about the diode mentioned a few postings back. Where would that diode be in the wiring? When I got my truck the connector for the compressor was missing, but the wires were still there. I put individual spade plugs on the wires and connected them to the corresponding spade pins on the compressor (R4 type only 2 wires). It runs/cycles (and doesn't run when the system is low so seems correct), but if there is supposed to be a diode in there protecting the other electronic elements I absolutely want to install it. The A/C is kind of inop at the moment (compressor runs, pressures seem OK on the gauges but not much in the way of cool air comes out) so I'm not using it, but I would really like to get it working.

Looks like this:

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Or this:

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Amazon.com: Dorman 85143 Electrical Harness - 2-Wire GM A/C Clutch with Diode Compatible with Select Models : Automotive

Buy Dorman 85143 Electrical Harness - 2-Wire GM A/C Clutch with Diode Compatible with Select Models: Wiring Harnesses - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[YakkoWarner]

OK so clearly I am missing this since the original connector was not present when I bought the truck. Does anyone sell the connector with the diode present?

 

[Sad Sack]

OK so clearly I am missing this since the original connector was not present when I bought the truck. Does anyone sell the connector with the diode present?

See post 12

 

[YakkoWarner]

See post 12

I was unclear in my question. Post #12 has the pictures - but doesn't say where to buy them. That is what I actually needed to know...