Need some a/c gurus

[1SlowFummins]

Background of the truck:

This is a 2006 f250 former powerstroke 5r110 truck that now has a 12v cummins and zf6. A/C was blowing cold and working great until I noticed a tiny leak in the coolant. The truck sat up for a few weeks and a friend needed to borrow a known working pcm to trouble shoot an issue with his truck. So he borrowed my pcm and put back. When I went to drive the truck again the a/c would not blow cold. I checked pressure and sure enough it had leaked down. I found the leak and fixed it. In the process of attempting to recharge the a/c system the clutch would not engage. I jumped the low pressure switch and still no go. Checked power at the compressor and none, checked power to the low pressure plug and it had power, checked power to high pressure switch and it had power. Checked the fuse under the dash and it was good, checked the fuse under the hood and it was good. This was fuse F2.23 and fuse F1.17. Last to check was the relay. I jumped pin 3 and 5 with the relay removed and presto the clutch engaged. I replaced the relay with a new relay and no go. So apparently the relay is not getting a signal to close the circuit. Any thoughts guys? No HVAC signal, no signal from pcm somehow? Or could it be that the new relay that I got it bad also?

 

[madmikeismad]

Background of the truck:

This is a 2006 f250 former powerstroke 5r110 truck that now has a 12v cummins and zf6. A/C was blowing cold and working great until I noticed a tiny leak in the coolant. The truck sat up for a few weeks and a friend needed to borrow a known working pcm to trouble shoot an issue with his truck. So he borrowed my pcm and put back. When I went to drive the truck again the a/c would not blow cold. I checked pressure and sure enough it had leaked down. I found the leak and fixed it. In the process of attempting to recharge the a/c system the clutch would not engage. I jumped the low pressure switch and still no go. Checked power at the compressor and none, checked power to the low pressure plug and it had power, checked power to high pressure switch and it had power. Checked the fuse under the dash and it was good, checked the fuse under the hood and it was good. This was fuse F2.23 and fuse F1.17. Last to check was the relay. I jumped pin 3 and 5 with the relay removed and presto the clutch engaged. I replaced the relay with a new relay and no go. So apparently the relay is not getting a signal to close the circuit. Any thoughts guys? No HVAC signal, no signal from pcm somehow? Or could it be that the new relay that I got it bad also?

Turn it on like you normally would, and test the signal wire for power, that will rule out the relay.

 

[NEVRNF]

Does your truck have a digital climate controll in the cab? Does your Tach work? I know on my conversion if there is no tach signal to the Ford ECM the AC will not turn on as it thinks the truck is turned off.

 

[1SlowFummins]

Turn it on like you normally would, and test the signal wire for power, that will rule out the relay.

Very true. I knew to jump 3 & 5 because they were the larger plugs so I knew they were the power. I will have to check and see which pin in the signal coming in and which is the signal going out. Im good with mechanical things but absolutely terrible when it comes to electrical.

 

[1SlowFummins]

Does your truck have a digital climate controll in the cab? Does your Tach work? I know on my conversion if there is no tach signal to the Ford ECM the AC will not turn on as it thinks the truck is turned off.

My truck does have digital climate control and it all seems to work great. All of the bottons work, the vacuum lines are changing correctly, a/c light is coming on when pressed, ect.

Its funny you mention the tach because it use to be solid and accurate but recently it has been jumping around as if it has vibrated outside clearance specs. I have revved the engine up to double check this but perhaps its not getting a solid voltage reading due to jumping around?? I will re-gap this weekend to stabilize and see if this works. If so you will be the man!! Never thought about tach signal. Im keeping my fingers crossed but i'm usually not this lucky.

 

[1SlowFummins]

Ok I found this. So as to contribute to the database a little and get some help, If I probe B2 on the engine harness and it has power then I know my computer is not at fault and is signaling to engage the a/c clutch circuit correct?

Lastly will I need to probe pin 1 or pin 2 for power at the relay? Obviously the relay will be removed so I should only have voltage in pin 1 when relay is removed...? I will also need to check for power at pin 2 but this will be with the relay plugged in correct? Please excuse my electrical ignorance.


AV: Air Conditioning (A/C) Relay Control Circuit
Introduction
AV: Pinpoint Tests

This pinpoint test is intended to diagnose only the following:

A/C clutch relay
A/C clutch relay control circuit
powertrain control module (PCM)

Air Conditioning Clutch (A/CC) Relay Connector

Pin Circuit
2 A/CCR (Air Conditioning Clutch Relay)
1 VPWR (Vehicle Power)

Powertrain Control Module (PCM) Connector

Pin Circuit
B2 A/CCR (Air Conditioning Clutch Relay)

DTC Description

P0645 = A/C Clutch Relay Control Circuit

 

[Lamont_24]

There might be a diagram of the internals of the relay printed on the relay itself that will show you which pins are which, like pull in, hold in, etc.

 

[1SlowFummins]

There might be a diagram of the internals of the relay printed on the relay itself that will show you which pins are which, like pull in, hold in, etc.

Yeah I have two relays and I remember one of them at least that had a diagram on the side. I run a medical clinic during the week and only have the weekends to crack the hood open on the ole f250. Currently driving an ole beater truck. Just trying to get as much info as I can so HOPEFULLY I can get this dang a/c fixed. These 90 degree 80% humidity days in south MS are killing me. Especially leather seats.... :/

 

[1SlowFummins]

I figured out the diagrams, makes sense now. I will test everything this weekend and report back. Thanks guys.

 

[1SlowFummins]

Does your truck have a digital climate controll in the cab? Does your Tach work? I know on my conversion if there is no tach signal to the Ford ECM the AC will not turn on as it thinks the truck is turned off.

It was the tach signal! Thanks again sir!