Air conditioning compressor stops running after few mins. ECU codes unknown.

[jousterde1]

My 2005 T1N van has issues with the AC system.
Air conditioning compressor stops running within anywhere from 3-15 minutes after AC is turned on.
Have to stop the engine and restart for it to work again, and again for few minutes. Connected iCarasoft MBII with Sprinter software and went to ATC/AC section. It shows proper temps on all sensors and proper Freon (134a) pressure in the system when compressor runs (according to shop manual). After a while it shows clutch coil OFF and pressure falling with error B1006-008. In addition when clearing the codes one persists: B1005-008 no matter if AC is ON or OFF.

I searched the internet for these codes and got nowhere. Did learn that these are "extended, manufacturer specific" and "B stands for body". Does anyone know what they mean?

I took apart the ATC module and re-soldered the relay under the temp knob, unfortunately this had not solved the problem. Please help.

 

[Midwestdrifter]

B1006 codes all reffer to compressor clutch wiring issues. -008 does not show in the diagnostic manual.
-007 is Clutch short circuit to + or open circuit
-005 is Short circuit to ground

B1005-007 and -005 refer to heater/booster errors (espar). No -008 listed. -007 is a short circuit on the heater harness to + or open circuit. -005 is short to ground on the espar wiring harness.

I would suspect that B1006-008 is ether an incorrectly reported code, or its any internal error code, which means an ATC malfunction.

 

[Midwestdrifter]

If you are desperate for AC, you can wire a switch to your compressor clutch control and provide it 12V directly (must be fused appropriately). You will also need to push the AC button on the dash.

 

[jousterde1]

Thanks for your reply Jonathan, great info . I will get under the van and check the wiring. If I get nowhere I will just add direct fused switch like you suggest.
The MBII says "code not found in the database" for both of these - wish they updated their software.

Before I saw your reply, this morning I did some more testing with AC gauge on low side and noted a strange behavior:
Static pressure of 105 psi (temp outside 88F), van sitting overnight. Every time the van is started the AC compressor always engages. The low side goes to about 40psi and stays around there for a while, AC cools nicely. After a few minutes it starts fluctuating: falls down to ~30 psi then up to 70+, then 30 and 70+ psi, and again, then just stays at around 70, starts climbing and at this point the compressor clutch is OFF. The cycle lasts around 15 seconds.
Also, I can speed up the start of the "fluctuation cycle" when I press the accelerator pedal - the pressure on high side spikes to over 29 bar (420 psi as reported by MBII) then the oscillation starts and compressor goes OFF.
If this was a wiring issue shouldn't compressor just shut OFF or keep going intermittent for longer than few seconds?
Another common reason for cycling is overcharge of system (online resources), but looking at 134a tables my static pressure is normal (105psi/90F).

Isn't 420 psi (high side) a bit too high and the over-pressure sensor shuts OFF the compressor? (no reports of that when reading the codes in MBII).

Thanks again.

 

[Midwestdrifter]

Sounds like an overcharge to me. If that isn't the case your clutch could be slipping (how is the air gap?). It could also be a bad TXV. The displacement control valve inside the compressor could also be bad.

 

[jousterde1]

Sounds like an overcharge to me. If that isn't the case your clutch could be slipping (how is the air gap?). It could also be a bad TXV. The displacement control valve inside the compressor could also be bad.

Not overcharged since the pressure stays at around 30-40 on low side when it works.
Checked compressor wiring: OK
The compressor clutch has proper gap and when engages doesn't slip. That leaves the TXV and control valve...
Since my ATC unit is still out I can actually hear the relay click when it releases the clutch coil. Code B1006-008 gets thrown as soon as I hear the relay click OFF.
Does anyone else have an idea what the -008 is?

 

[BrennWagon]

I’d think that there may be an overcharge, some air, or other contaminant in the system with the system pressure occasionally going crazy like that. If you take it to a shop that can service AC systems and have them evacuate and refill it you might find your cure. Is it possible the PO serviced the AC themselves and goofed something?

 

[Midwestdrifter]

Most of those undocumented codes are caused by internal faults inside the unit. At least that is my experience. You may try a different scanner, as this could be a bug in the unit software.

 

[jousterde1]

So my AC problem is fixed, see the rest of this topic for symptoms. Here is what I did, hopefully it will help someone out there.

I can tell you now you cant diagnose AC without a gauge set (low and high gauges). It was only $40 on amazon/ebay, well worth the price. A shop will charge you double that just to hook theirs up and renting isn’t much cheaper than buying. Read up on how AC works and what common problems are and general rules on diagnosing with gauges. Remember to keep all valves closed so you don’t drain your system or cause injuries. Glasses are a must, gloves recommended – this stuff will freeze-burn you if a hose ruptures, etc.

Other things needed will be: soldering iron, core flux solder, infrared thermometer ($15 ebay/amazon) water spray bottle and computer duster can (as used in PC shops to blow dust out of PC cases).

First thing I did was to remove ATC module and reflow/re-solder the AC clutch relay (under the temp set knob). Unfortunately that did not fix my problem, as it did for others.
Next, I hooked up the gauges (close all valves) and checked static pressure – normal as for 134s chart, so no apparent leaks. Then started the van and let it run with AC on for a few minutes (doors open, fan on high) until pressure stabilized. The pressure High readings were near normal for ambient temp (see chart) so that eliminated the compressor and its valves. The AUX fan (front, behind grill) would come ON when the High pressure reached about 300psi. So, fan is good. Low pressure would occasionally dip to about 25psi, than back to 40psi (proper for ambient temp at the time). Had to restart van when I got the “fluctuation, then clutch off” symptom.
Next, removed the grill, got the thermometer and scanned the condenser for “cold spots” that would indicate obstructions inside, none found - condenser good.
Then to evap and TXV. Thankfully in my 2005 Sprinter the TXV is just behind windshield wiper motor, easy access. Checked temp delta between in and out of its evap side, was about 20F, evap normal.
Did TXV test: took the duster can, turned it upside down (freeze mode) and blasted TXV for about 5 seconds to cool it while watching the High pressure gauge: moved UP about 15psi, good. Next used spray bottle filled with hot water and sprayed the TXV for about 10s to heat it while watching High gauge, it moved DOWN about 15psi. So, TXV valve is good. No movement or very slight – replace.

That left the last component: the ATC module. I recall Midwestdrifter mentioning that the codes I’m getting were not published, so most likely internal module error codes. Bought used ATC module off ebay thinking I can resell it if that’s not it. After just plugging it in and starting the van I noticed a change, no more ATC errors. Let the van run for whole 30 minutes, no weird “fluctuation” the compressor clutch no longer stayed OFF (did cycle tho, as is should) and the temp out of outlet stayed at around 41F. After assembly of the console I took the van out for an hour long run and the AC hasn’t failed. Will keep the old ATC for spare parts, refurb on ebay was about $100. Total cost to fix: $150 plus many hours of learning and working on it. If I were to consider that most auto repair shops will replace every single component in AC system until they arrive at the problem – saved myself thousands. Hope this will help you do the same.
Thanks again to Midwestdrifter and others on this forum for their knowledge and time taken to share with us.

PS. The High pressure never went over 300psi, and this was on startup cold before the fan kicked in and would not go pass 260 with 90F ambient temp. So my old ATC MBII reading of 29bar (420psi) was also misreported. Should have gotten the gauges right away...

 

[jousterde1]

Here is ambient temp/pressure chart in PDF for reference/printout.

 

[marklg]

Here is ambient temp/pressure chart in PDF for reference/printout.

Where did the chart come from? It stops at 110F. It regularly gets to 115 in Phoenix and sometimes to 120. Those numbers would be useful.

Regards,

Mark

 

[Midwestdrifter]

That chart is based on an average evap temp of 28-33C above ambient. At 120F ambient that would be 79C evap temp, which corresponds to ~380psi for R134a.

 

[altide8]

B1006 codes all reffer to compressor clutch wiring issues. -008 does not show in the diagnostic manual.
-007 is Clutch short circuit to + or open circuit
-005 is Short circuit to ground

B1005-007 and -005 refer to heater/booster errors (espar). No -008 listed. -007 is a short circuit on the heater harness to + or open circuit. -005 is short to ground on the espar wiring harness.

I would suspect that B1006-008 is ether an incorrectly reported code, or its any internal error code, which means an ATC malfunction.

I’m having some issues with my compressor turning off after cooling effectively for a while. I noticed that everything was cooling properly after each restart so I ran codes. I’m getting b1005-005 it says compressor clutch has short to ground. Is this likely the ATC?

 

[Midwestdrifter]

I’m having some issues with my compressor turning off after cooling effectively for a while. I noticed that everything was cooling properly after each restart so I ran codes. I’m getting b1005-005 it says compressor clutch has short to ground. Is this likely the ATC?

I am not sure. My first thought is that its a faulty clutch (shorts when its warm). I would also check the clutch power wire to make sure its not chafing anywhere.

 

[altide8]

I am not sure. My first thought is that its a faulty clutch (shorts when its warm). I would also check the clutch power wire to make sure its not chafing anywhere.

I’ll check the wires first. If I clear the code the compressor turn back on. Is there significant risk in damaging anything else if it is the clutch and I continue to reset the error long enough to get me home? I’m pretty far from home at the moment.

 

[Midwestdrifter]

I don't think you're likely to cause any damage other than possibly continuing degradation of the clutch. In a pinch you can hardwire the compressor clutch on with a 10 amp fused circuit. This is an emergency/temporary fix only as the overpressure protection will not be present.