New a/c compressor/ new high low switch sensors, all fuses ok, can get power to a/c compressor if I jumped the a/c clutch relay. Can’t figure out why I’m not getting a ground signal to close relay in!!?? Ac on max full speed, low and high side psi around 98

 

Have you checked the in cabin fuse panel for a blown fuse? If the fuses are all good, you can back probe the wires on the pressure switches to see if currant is flowing threw them. Key on, AC switches to run position when testing the pressure switches.

 

yes buddy, all fuses good, have 13.8 volts to both switch’s with truck on and running ac max wide open. Bypassed my ac relay and the compressor kicks on.

 

I am going to ask you questions. Your job is to answer them. Just use a test light for now to check power, put alligator clip on negative battery terminal. Probe positive terminal to verify the test light illuminates. There is no A/C clutch relay on these trucks. The compressor is engaged with a 12V NOT a ground signal. It grounds through the black wire on the pigtail to the clutch...which goes into the assend of a diode to ground.

Is your A/C system fully charged or does it have a charge at all?

Does your blower fan work?

Do you have 12V at the purple wire under the hood near the blower motor when in A/C mode (max or regular)? This is a single wire that comes from the cabin out to underhood at a small connector.

Do you have 12V at the pressure switch from the purple wire?

Do you have 12V out of the pressure switch on the red/yellow wire? Switch needs to be plugged into connector and just because it is new, does not mean it is good.

 

[QUOTE=Hit Man X;19226831]I am going to ask you questions. Your job is to answer them. Just use a test light for now to check power, put alligator clip on negative battery terminal. Probe positive terminal to verify the test light illuminates. There is no A/C clutch relay on these trucks. The compressor is engaged with a 12V NOT a ground signal. It grounds through the black wire on the pigtail to the clutch...which goes into the assend of a diode to ground.

Is your A/C system fully charged or does it have a charge at all?

Does your blower fan work?

Do you have 12V at the purple wire under the hood near the blower motor when in A/C mode (max or regular)? This is a single wire that comes from the cabin out to underhood at a small connector.

Do you have 12V at the pressure switch from the purple wire?

Do you have 12V out of the pressure switch on the red/yellow wire? Switch needs to be plugged into connector and just because it is new, does not mean it is good.[/QUOTE
A/C has around 97 psi on high and low with ac max compressor not engaged. Plenty enough to get it to engage. Blower fan works but hot pig tails assuming it’s on it way out. Have voltage on purple wire when ac is on max. Yes also have have power red/yellow. Replaced them with known good parts off another daily driver. Switch’s low and high verified good .

 

Check for voltage off the high switch. Green/orange.

 

13.5v on high switch green/orange

 

I did just put a new pcm in the truck from full force diesel. Vdh5. Reason was I kick my hydra cable pulling the chip a quarter out of the pcm fired both. I was in New York at the time and there was no reason for ac. Back in Florida now and ac is needed. Headed ti out a Solas computer on it as we speak.hopley can get more info .

 

Check for voltage at grey/white to compressor connector. You may have an issue in the diode area or just a crap connector at compressor. Green/orange runs to that diode and that is where the grey/white begins that runs out to the compressor.

Check for continuity to ground on black wire (socket side) of the A/C compressor connector. You will need a DVOM for this.

There is a grey connector by the starter solenoid. It has space for eight pins, only has five. You may want to unplug this, clean it with Deoxit. Reconnect.

 

no voltage on grey to compressor . The connection is good at compressor. I sent power 6 inch out from connector on the wire with power probe and clutch engaged. I’ve unplugged and messed with the 4 wire connector and still no power.

 

Can you back probe the grey/white? It could be broken internally. You may have to open that harness and look for the diode and check for power there. Check the ground continuity too, but sounds fine if you back probed the grey/white and hit that with 12V and compressor kicked on.

At least you know where power terminates currently. You have to figure out why it does not flow from the green/orange to grey/white. A diode is just like a faucet tap allowing power flow in only one direction.

 

my truck is a 02 7.3 motor. It has a A/C clutch relay on driver side under the hood. I have powoer coming in. The pcm controls the relay when requested. Traced everything back to the pcm. I believe the problem lays there. Have a friend with the same pcm going to swap them out and have a 100% answer. I can jumper the relay with a wire and ac work as it should.

 

Oh, you have a Super Duty?? I thought you had a 94-97, sorry! I was looking at schematics from it, I do not have them for the SD.

You could swap relays and see if you just have a bad relay.

 

just swapped out pcms with a for sure good one. Ac clutch kicks right on! The new one from Desiel technology of Chattanooga. www.dieseltechchatt.com was not sending signal to close the relay! Cost me hrs of tracking it down and verifying it and the *******s still want to hold $700 on my card. Luckily my friend is letting me hold on to his till mine gets back so I’m not out a truck. Or I would have had to let them hold $700 to send me one before I sent the bad one back or be out a truck till the test and sent one. A little up setting since it’s only 1 month old.