[eelley]

Hello All,

My AZD van died in traffic last week. Bummer. It is currently blowing fuse 24, (V-Latch) whenever HV is enabled by either plugging in the van to an EVSE or enabling HV in diagnostic mode. Sheet four of the schematic indicates that the following circuits that are protected by this fuse:

HV Battery Heater (Section 2) - I'm able to turn it on manually in diagnostic mode, and the fuse does not blow.
HV Battery Heater (Section 3) - I'm able to turn it on manually in diagnostic mode, and the fuse does not blow.
Reverse Lamp - I'm able to turn it on manually in diagnostic mode, and the fuse does not blow. Reverse lights come on when the fuse opens.
Vacuum Pump - I'm able to turn it on manually in diagnostic mode, and the fuse does not blow.
DMOC - Unplugging the control harness at first, prevented the fuse from opening, but now does not have any effect during the second day of testing.
Cabin Heater - I did not test this since it is unrelated to the symptom.
Air Conditioner - I did not test this since it is unrelated to the symptom.
VCU (C232S - DRVP1) - When this fuse blows, the diagnostic software reports 2.9 volts which is expected. So I am assuming this is where the VCU monitors the 12 battery.
VCU (C232S - DRVP2) - When this fuse blows, the diagnostic software reports 2.9 volts which is expected.

I am stumped. I was hoping this was the common F35 WOC repair (F24 opens wether or not the WOC is connected or not.) Perhaps there has been a revision to the schematic and there is another circuit that is not included here? Obviously, I am overlooking something. There is not an active short on the VLatch bus.

Has anyone seen this before? The van has been running fine for two years with no problems. I did have a stuck contactor back in 2019 which required the pack to be lowered and opened, the stuck contactor was replaced and the cells in ESS2 were manually charged and balanced because ESS2 fell outside the 10% range for ESS1 and ESS2 to operate. All this was caused by a wacky ground connection between the DC-to_DC converter, battery and frame. This time around I am not getting any stuck contactor DTCs...thankfully.

The van is currently at 70% SOC and each cell is sitting at approx. 3.8V.

Any help would be appreciated.

Eric

 

[eelley]

Here is a screenshot of the DTCs after the fuse blows. There are no DTCs, wrench or turtle indicators prior to the fuse blowing.Nor is there any after the fuse is replaced and the key is cycled and placed into ACC.

 

[iura]

hi, can i ask, did you solve your problem, what was the problem?
I can share different schemes, maybe it will help.

 

[eelley]

Yes, the problem is solved with a large dose of help from the folks at Inductive Automotive in Tolland, CT! It turns out that the vacuum pump solid state relay (C302) located under the hood on the firewall was defective and would blow fuse F24. Losing F24, and key cycling the vehicle enough times during troubleshooting (thanks for that info, Dave), caused the Axiomatic high-voltage discharger unit (ADU) to fail. If the module fails due to excessive key cycling or a strong breeze passes over the car (no joke the ADU is crap), the resistors will burn open and you will receive DTC's that indicate there is a fault in the Primary Interlock safety loop (P18A81) and/or the precharge timing is off. If you open the high voltage junction box, where the ADU is located, and smell burnt resistors, then most likely the ADU is bad (credit to Dave).

I was able to buy a spare ADU off eBay. Both Inductive and I are actively researching the failed parts in the ADU. Inductive has sourced the power resistors that burn open. I am researching the shorted transistors on the PCB which shorted in my unit causing the remaining resistors to remain in circuit and messing up the precharge timing because there is basically a low resistance short across the high voltage buss (thanks again Dave.)

Many, many thanks to Dave A. and the ability to phone a friend. And many, many thanks to Jon, Dennis and Joe at Inductive Autoworks in Tolland, Connecticut. I wish we met years ago when I had to drop the battery pack due to stuck contactors in ESS2 and then had to manually rebalance that half of the pack.

If you live in the Northeast US and have a problematic Azure Transit, give them a call straightaway!!

Eric

 

[iura]

Thanks, I'm glad the problem is solved. Any information is very helpful.

 

[iura]

Hi Eelley,
Can you explain to me which module is HVAC, it must be climate control, but there is no any information in HV scheme about it? May be this is regular Ford Transit module?