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How To Get Compressor To Come On?

EverydayDiesel on Mon May 12, 2008 9:03 PM User is offline

Year: 2001
Make: Dodge
Model: Ram
Engine Size: I6Diesel
Refrigerant Type: R134a
Ambient Temp: 70
Pressure Low: 75
Pressure High: 75
Country of Origin: United States


I figured out how to get what seems most of the refigerant out of the can but I still cannot get the compressor to come on.
Ive checked and swapped both the a/c fuse and clutch relay.

What options do I have at this point? How can I get the compressor to come on?

Compressor, condenser, drier (including new low side pressure switch), and liquid line are all brand new OEM parts.

Chick on Mon May 12, 2008 9:45 PM User is offlineView users profile

Did you pull a deep vacuum and let the vacuum pull in as much refrigerant as it can? If so, it should start on it's own.. If not, you need to pull the vacuum..If you did, you can jump the low side switch (two wire switch on the low side) if it has one.. I can never remember which Chryslers have accumulators and which have dries/expansion valves.. If that new side pressure switch is two wire try jumping that..If it doesn't come on, make sure you have 12v going to it..There are under dash fuses as well as under hood fuses..Let us know what you find..75psi should be more than enough to start it...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

EverydayDiesel on Mon May 12, 2008 10:26 PM User is offline

im stumped at this point. fuses and relays good. I have a robinair 5cfm pump that i ran for 45 minutes before putting the first can in. (i did it again if you saw my other thread)
If I jump the driers low pressure switch across and the compresor does not come on then I guess ihave an electrical problem.

TRB on Mon May 12, 2008 10:49 PM User is offlineView users profile

You have a low pressure switch and a high pressure switch feeding the PCM on this vehicle. Both low and high trip the PCM leg which trips the clutch. I would not have jumped either of these switch's. Not saying you have but jumping these switch's can damage the PCM. I would get a wiring diagram of this vehicle and using a test light track down where there is a loss of power.

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Contact: ACKits.com

TRB on Mon May 12, 2008 11:01 PM User is offlineView users profile

Locate low pressure cut-out switch on suction line, near firewall. Ensure system pressure is correct. Disconnect negative battery cable. Disconnect low pressure cut-out switch connector. Place a jumper wire across terminals of low pressure cut-out switch harness connector. Connect negative battery cable. Connect manifold gauge set. Set A/C-heater controls to A/C position. Start and operate engine at idle speed. Using DVOM, check for continuity between terminals of low pressure cut-out switch. Continuity should exist when suction pressure reading is between 15-25 psi (1.1-1.8kg/cm2 ). Continuity should not exist when suction pressure reading is 7-13 psi (.5-.9kg/cm2 ) or lower. If continuity is okay, repair open or short in Light Green/Gray wire between low pressure cut-out switch and PCM. If continuity is not okay, replace faulty low pressure cut-out switch.


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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

EverydayDiesel on Tue May 13, 2008 12:15 AM User is offline

is it hurting the drier each time I pull a vacuume on the system? Ive pulled a vacuume twice already. It is brand new and It is the very last thing I installed before hooking up the pump

TRB on Tue May 13, 2008 12:18 AM User is offlineView users profile

No

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

chris142 on Tue May 13, 2008 10:58 PM User is offline

Stupid questin..........Does the horn work? Those trucks use the horn fuse under the hood to power the compressor clutch.

EverydayDiesel on Wed May 14, 2008 9:02 PM User is offline

The compressor clutch has its own fuse and it is good. I checked ALL the fuses and they were good.

I shorted the low pressure side together and with 70 psi (low side) the compressor still did not come on.

Any other ideas on why this compressor is not coming on?

EverydayDiesel on Thu May 15, 2008 12:07 AM User is offline

Ok I have 12volts on the connector going to the compressor (solid black wire) when I turn on the switch inside the cab.
I also have a good ground on the yellow/black wire going to the compressor.

The compressor is brand new, does that mean that the clutch is bad? Could it be anything else before I send it back?

ice-n-tropics on Thu May 15, 2008 9:13 AM User is offline

One possibility is the following:
The compressor clutch wire harness has a diode imbedded about half way inside the shrink tube. The 1000 volt rated diode blocks the negative voltage created by the clutch magnetic field collapsing inward back into the windings when the current flow suddenly stops. If the wire harness is connected with reverse polarity the diode is blown (open circuit ) and continuity is lost. Also, if the battery or positive circuit is arched the diode can be destroyed. Welding on the truck chassis without disconnecting the battery terminals also blows the diode.
Hope this helps,
Old IV guy

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Chick on Thu May 15, 2008 1:45 PM User is offlineView users profile

Before you go sending the compressor back, check the coil. Should have between 3 and 4 ohms, if you do, the clutch should engage if the electrical system is OK. Like Ice said, the diode could be blown, or like many cars, the computer sends the "ground" to the compressor thru the relay, try swapping the compressor relay with a similar one. There is usually a couple the same in the relay box..Just a thought...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

JACK ADAMS on Thu May 15, 2008 1:51 PM User is offline

I would also check the clutch gap…. Tap on the front hub of the compressor with a long extension, if it comes on then readjust the clutch gap. These diesels use the Sanden compressors and are well known for ware. Gap should be at leased 16-18 thousands. Hope this helps and good luck..

EverydayDiesel on Fri May 16, 2008 7:54 PM User is offline

I took it back to dodge today and had the compressor replaced with a brand new one.

I did all the steps, pulling vacuum and adding refrigerant etc etc...

I go to turn the truck on as well as the A/C but the clutch still does not engage.

I have 14v on the harness going to the pump and I have replaced the fuses and the relays for the a/c clutch.

Im stumped, this thing is suppose to work.......
Whats the next step?

Edited: Fri May 16, 2008 at 7:55 PM by EverydayDiesel

EverydayDiesel on Fri May 16, 2008 8:40 PM User is offline

I found out that the connector from the truck was bad. When you would plug in the compressor harness it would push the terminals out of the connector.

NOW IM BLOWING FUSES!!!!!!!!
Its fine until I turn on the compressor and thats when the fuse pops.

Any ideas on where to check?

Chick on Fri May 16, 2008 9:37 PM User is offlineView users profile

I would check right there, sounds like the pins are shorting out..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

EverydayDiesel on Sat May 17, 2008 12:10 AM User is offline

No way I got two bad compressors in a row from dodge. They even have different part numbers (they said it was a revision). My old pump ends with A05 the first new pump ended in A08 and this new pump I got today ends in A07

I disconnected the harness from the compressor, started the truck, turned the a/c on and the fuse was still good.

I took some alligator clips and hooked up my old pump (just laying on the ground) the clutch locked up like it is suppose to. (but this is with no belt load on the pump remember it was just laying on the ground)

Then I took the new compressor and hooked it up, started the truck and turned it on and the fuse blew immediately.

I havent done anything to the pump except bolt it up, hook the lines up and plug in the harness. Do I have to prime or turn it a few times to get it to work? Maybe the load is too much since it is new and thats why its popping fuses?

I also have 3.2 ohms of resistance on the old pump and on this new one i have 0.1 ohms

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