So the IPM ( PTC #1 ) where exactly is it?? Can it be reset or changed??

[PWong]

When checking the voltage with a voltmeter, always probe a known good ground with the black lead.
Then probe the point to be checked with the red lead.

 

[sandmanxx]

Have to be trmw

Thanks Mr Wizard !

I know - u want to find the answer.. Me toooooooooooooooooo :{

 

[sandmanxx]

Just wanted to keep you informed.. Will do / "recheck" the above "list/checks" Friday

As for ground I am using the ground frame bolt by the battery that is a accessary ground point. Also checking out my heater dash switch as that may be other issue lol..
I am thinking it was the PTC or PIN 30 fused battery thing..

I just now starting writing everything down that I do.. lol..

 

[PWong]

Fuse #16 and PTC #1 are two different circuits.

 

[PWong]

Find out the reason for 12V when key off and nothing when key on.

 

[PWong]

P0646 = issue with A/C Clutch relay coil circuit.
Fused battery supply would be the PTC#1 when feed power to relay coil (pin 85).
Relay coil (pin 86) would be grounded by ECM when ECM request the compressor to run.

 

[sandmanxx]

P0646 = issue with A/C Clutch relay coil circuit.
Fused battery supply would be the PTC#1 when feed power to relay coil (pin 85).
Relay coil (pin 86) would be grounded by ECM when ECM request the compressor to run.

You prob know but just FYI where I came up with what I am doing



P0646 LOW VOLTAGE DETECTED AT THE A/C CLUTCH RELAY

Details Written by Michael Nelson Category: OBDII Cummins Error Codes C Published: 03 December 2012 C Created: 03 December 2012 C Last Updated: 03 December 2012

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P0646 LOW VOLTAGE DETECTED AT THE A/C CLUTCH RELAY

When Monitored and Set Condition:

When Monitored: When the ignition is on.
Set Condition: When the signal from the A/C Clutch output does not match the signal from the A/C Clutch
feedback.

POSSIBLE CAUSES
• A/C CLUTCH RELAY
• LOOSE CONNECTION
• FUSED BATTERY SUPPLY
• (C13) A/C SIGNAL CIRCUIT OPEN
• (C13) A/C SIGNAL CIRCUIT SHORTED TO GROUND
• INTERMITTENT CONDITION
• ECM

DIAGNOSTIC PROCEDURE
1. Ignition on, engine not running. With the DRBIII®, actuate the A/C clutch relay. Can you hear the Relay clicking?
Yes --> Go To 2
No --> Go To 3
2. Actuation still running. While the relay is clicking, wiggle the wiring harness and connectors throughout the circuit. Does this interrupt the clicking?
Yes --> Repair the loose connection. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No --> Go To 3
3. Remove the A/C Clutch Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary. Measure the resistance between terminals 85 and 86 of the A/C Clutch Relay. Is the resistance less than 100 Ohms?
Yes --> Go To 4
No --> Replace the A/C clutch relay. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
4. Ignition on, engine not running. Measure the voltage on the Fused Battery Supply circuit in the PDC. Is the voltage within 1 volt of battery voltage?
Yes --> Go To 5
No --> Repair the open Fused battery supply. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
5. Turn the ignition off. Disconnect the ECM harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance of the (C13) A/C Clutch signal circuit between the PDC and the ECM harness connector. Is the resistance less than 10 Ohms?
Yes --> Go To 6
No --> Repair the open (C13) A/C signal circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
6. Measure the resistance of the (C13) A/C Clutch signal circuit between the PDC and battery negative. Is the resistance greater than 100k Ohms?
Yes --> Go To 7
No --> Repair the (C13) A/C signal circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
7. Reconnect the ECM harness connectors. Using the DRBIII®, actuate the A/C Clutch Relay While monitoring with the DRBIII®, use a jumper wire to connect 12 volts to the relay signal cavity (85) in the PDC with the relay disconnected. Did DTC P0647 set?
Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No --> Replace the ECM. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

 

[PWong]

So test step 4 failed. You didn't have 12V at pin 85, PTC #1 was open.
Try run a 5A fused battery power to pin 85 if you don't want to fix the PTC on the board.

Still you need to get 12V at pin 30 when key ON.
The power was coming from fuse #16.

 

[sandmanxx]

Still here..

Can you believe in San Antonio it was almost impossible to find a "insulation piecing clip" lol..

Oreilly autozone, pepboys etc no! HVAC "public store" no (order), electrical supply that I went to NO (order), Lowes and Home depot no!

Grangers had "ONE" lol..

I know a needle would work but I just wanted a real clip if I was going to go a whole ECM / IPM connecter checking different things out! "for various reasons"

 

[sandmanxx]

Have the IPM out and checking the back side pins "on the unit".. Must say at first it does not look like the pin outs match the print PDF file..

ALL 4 pins register in back - guess that's a good thing I hope.. Well recheck in AM has I am dead tired. I did note that one or two pins on top checked out on bottom
and also give a 200 ohm read on a pin "way across" the same connecter ie: IPM C5

Guess I can find out where fuse #28 pin out is in relation to the relay pin

** Question - what is the quick link fuse on driver side battery + cable..

** and the dam AC chapter talks of a diode in the harness line just like the quick line fuse ??? #@$%!

Going to verify PIN #30 on back on IPM and check cable to harness side compressor - then connect to compressor and put direct 12+
Going to check 12 volts and ground on both compressor cables just because.
Isolate and fire clutch first "again"

Going to check and clean up G120 circuit ground engine block ground for this circuit,
Fix the two ground to air take header grid.. THEY aren't bolted up after putting in new injectors..

Guess I will check the ground pin on all 7 IPM connectors since I have it out.. Also connectors are getting hit with CRC electrical contact cleaner.

The diagrams say the PTC#1 fuse is after fuse #28 and before the relay.. Really wish I could have a look under the fuse at
the circuit board..

 

[sag2]

I'm still a little confused by your observations. Can you provide an observation to each test below. I numbered them to make it easier. Also having this tool helps as you are plugged live into the circuit with the relay also in the circuit. You can test voltage or apply voltage for each pin via the terminals coming out the side of the tool.

Here is the wiring diagram that might make it easier to understand. The control side of the relay pins 85 and 86 are controlled by the ECM. Actually pin 85 should be hot with key on only. The ECM grounds pin 86 to close the contacts on the relay, pins 30 and 87. Pin 30 should be hot all the time. Pin 87 will only be hot when the relay works properly.

So this is what I would do.
1). Jump battery voltage to pin 87 with the relay removed, the compressor clutch should click. If yes, the wiring to the clutch, the clutch, and the clutch ground are good.

2). Next check for voltage at pin 30 with the relay out. Yes, fuse 16 is good and the wiring inside the PDC is good.

3). Next check for voltage with the relay out at pin 85 with the key on. Good, the PTC and wiring inside the PDC is good.


Here is where it might get tricky. If you have no voltage key on at pin 85 normally you should be able to jump voltage to pin 85 with the relay installed, but if the PTC is blown, the ECM may be monitoring that and never ground pin 86. Also without a DRBIII to actuate the circuit it makes it harder to diagnose.

I understand that you have voltage on step 2 only with the key off. That does not make any sense to me as it is connected directly to the battery through fuse 16.

Also, I may have missed it, but did you replace or swap the relay with a known good one?

 

[sandmanxx]

Thanks

1. 87 jump:

No with key off / on !

2. pin 30 volts:

12+ with key off
No with key on

3. Pin 85 volts with key ON

NO..
also NO with key off!

Starting to look like everything is pointing to the board. I think I may have 2 diff problems or not as for fuse box. Water / moisture getting in it and maybe something fried my AC circuit in board.. Maybe not.. Honesty I have driven the truck without the wheel well liner in - when working on truck. PLUS it's been a year since I used my AC so I really don't know when the problem happened!

My heater switch is questionable as well. Replaced the blubs and still no lights coming on when hit mirror heater or ac / etc.. Yes the blower works - and very well as I took out the HVAc and fixed all doors with heatertreater doors /etc..

I isolated compressor I fired the clutch more then several times. Changed out harness connector the compressor - that's was my first thing I did in beginning. The #30 relay socket is good to back of fuse box. The #30 wire in backside fuse box checked good. The #30 pin wire checked good to the harness connector side of compressor. The ground at same point to G120 is good. The compressor side
"connector wire" reads good across the compressor connecter. But when I check #87 to ground top side at relay with compressor connectors all plugged in I get 97+ ohms ??

Anyway I can try the last step as for hot wiring #87 with relay in.. But it looks like I have circuit board issues.. I have no problem looking at the board as I have seen one taken apart online..

*** But most of all have need to make a relay with a AC thermostat or other I have no problem.. I just want my AC back until!

Note: FYI don't think my heater switch is working either. Yes the blower comes on but the led lights don't work.. Replace all 3 and still done come on when
turning on a/c or "mirror heater"..

** insert: FYI I have had a few loss of power down data due to ECM loosing power of a "period" of time.. I had loose cables and the positive cable would come off at "some" time and when I pooped the hood for other reasons I found the positive one positive off. Basically while driving around positive cable came off! How long it was off I don't know.. Drivers side!! Thus guess system was prob over charging passanger battery!

Ordering a relay test kit this eve lol!

 

[PWong]

Here is where it might get tricky. If you have no voltage key on at pin 85 normally you should be able to jump voltage to pin 85 with the relay installed, but if the PTC is blown, the ECM may be monitoring that and never ground pin 86.

I think ECM just monitors the A/C Clutch Control signal when key on. It's looking for a high signal (12V signal).
It would not tell whether it's coming from the PTC or not.
As far as it didn't trigger p0646, it would ground pin 86 when A/C Clutch was requested.

Also you can ground pin 86 to actuate the relay coil circuit.

 

[PWong]

Thanks

1. 87 jump:

No with key off / on !

2. pin 30 volts:

12+ with key off
No with key on

3. Pin 85 volts with key ON

NO..
also NO with key off!

Starting to look like everything is pointing to the board. I think I may have 2 diff problems or not as for fuse box. Water / moisture getting in it and maybe something fried my AC circuit in board.. Maybe not.. Honesty I have driven the truck without the wheel well liner in - when working on truck. PLUS it's been a year since I used my AC so I really don't know when the problem happened!

My heater switch is questionable as well. Replaced the blubs and still no lights coming on when hit mirror heater or ac / etc.. Yes the blower works - and very well as I took out the HVAc and fixed all doors with heatertreater doors /etc..

I isolated compressor I fired the clutch more then several times. Changed out harness connector the compressor - that's was my first thing I did in beginning. The #30 relay socket is good to back of fuse box. The #30 wire in backside fuse box checked good. The #30 pin wire checked good to the harness connector side of compressor. The ground at same point to G120 is good. The compressor side
"connector wire" reads good across the compressor connecter. But when I check #87 to ground top side at relay with compressor connectors all plugged in I get 97+ ohms ??

Anyway I can try the last step as for hot wiring #87 with relay in.. But it looks like I have circuit board issues.. I have no problem looking at the board as I have seen one taken apart online..

*** But most of all have need to make a relay with a AC thermostat or other I have no problem.. I just want my AC back until!

Note: FYI don't think my heater switch is working either. Yes the blower comes on but the led lights don't work.. Replace all 3 and still done come on when
turning on a/c or "mirror heater"..

** insert: FYI I have had a few loss of power down data due to ECM loosing power of a "period" of time.. I had loose cables and the positive cable would come off at "some" time and when I pooped the hood for other reasons I found the positive one positive off. Basically while driving around positive cable came off! How long it was off I don't know.. Drivers side!! Thus guess system was prob over charging passanger battery!

Ordering a relay test kit this eve lol!

It's a can of worms. Lol

 

[sandmanxx]

:{ :{ #@$%!

 

[sag2]

I'm still a little confused. You can actuate the clutch by jumping voltage where? At the clutch connector, but not at pin 87 in the PDC? How about from connectors C112, C110, and C130? If you can jump it at the compressor connector it means the G120 ground is also good.

Also if you have the PDC out you should be able to trace the circuit from pin 30 to the battery lug on the PDC. That lug is usually the problem with the P2209 power down at speed if it isn't the battery cable itself at the battery.

 

[sandmanxx]

Ok

New "motorcraft" batteries

My starter solenoid didn't like the old "bad cell" batteries

Still only get voltage at pin #30 when key on

Now get 12V at 86 with key off or on lol.

As for pin 87 cable to compressor you make a point. I check the cable run from back side of fuse box to the harness side connector at compressor "ohms"
was basically 2 +/- ohms. Did not break that run down. Checked end to end.

Did check harness side ground at compressor and it was solid..

I fired the clutch with it isolated and running a ground lead from the compressor connecter pin and clipping it to block - then battery 12V to connector hot pin!

I then connected the compressor to harness wire and plugged the run back in to the fuse box..

Checked the 87 pin at relay (relay out) to ground and got 95 +/- ohms..

 

[sandmanxx]

Simple question as I am arguing with my dad on the relay pin outs and the dodge 2004 PDF manual ( which came from this site) so..

He is saying the relay pin out are wrong and don't agree with the dodge wiring diagram.. We all know not all the wiring info is correct - but as
for this circuit and the ac wiring I "assume/take it" that they are correct are it would have been noted and someone would say something!

Am I correct or not??

Basically he is saying the relay don't wok the way it has it in the diagram.. But I am telling him it's because my circuit "most likely isn't normal!""

RELAY IN HAND PIN OUTS

87 87A 85

86 ...... 30

 

[sandmanxx]

Just a note to be clear - you know I was in middle of charging and have maybe 1.5 cans in. That should be enough. AC gauges hooked up I get static reading that should work lol.

Don't remember what they where

Can we do this force the pressure switch to kick in the compressor to check??

 

[PWong]

Still only get voltage at pin #30 when key on
That's great.

Now get 12V at 86 with key off or on.
That's good too.
For relay operation pin 85 and 86 are interchangeable.
So PTC was good in sending power to pin 86.
Circuit C13 (LB/OR wire) would be on pin 85 now.

As for pin 87 cable to compressor you make a point. I check the cable run from back side of fuse box to the harness side connector at compressor "ohms"
was basically 2 +/- ohms. Did not break that run down. Checked end to end.
So the wire from pin 87 up to harness connector was good.

Did check harness side ground at compressor and it was solid..
So the harness side ground was good.

I fired the clutch with it isolated and running a ground lead from the compressor connecter pin and clipping it to block - then battery 12V to connector hot pin!
So the clutch was good.

I then connected the compressor to harness wire and plugged the run back in to the fuse box..

Checked the 87 pin at relay (relay out) to ground and got 95 +/- ohms..
So the harness connector was defective!!!!!!!!!!!!!!