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Dvorak
Senior Member

United States
52 Posts

Posted - 10/31/2013 :  05:43:34 AM  Show Profile  Reply with Quote
I have a bad ECU on a Wabco full power brake system (12v coming into it but no voltage going to one of the motors on the back side). My question is this: Have bad motors been burning out the ECU's and if so, should I be replacing the entire HCU? I'd hate to install a new computer only to have it burn out right away. Also, I've searched the previous posts but I've been unable to locate a part number to replace the pump motors. Has anyone found anything on these? Thanks in advance.

Dvorak
Senior Member

United States
52 Posts

Posted - 11/19/2013 :  04:08:37 AM  Show Profile  Reply with Quote
Here's an update on what I've found for this vehicle: I replaced the ECU and unfortunately, the problem still existed. I ended up ordering and installing a new HCU and that took care of all my problems. Before I returned the other one for a core, I decided to dismantle it to see inside the belly of the beast to try and learn something about it. When I pulled out one of the pumps, it sort of fell apart in my hand. I then hooked up the corresponding motor to voltage and it sounded a lot different than the other one. I'm not a certified failure analyst by any means, but from the evidence I've seem, I believe that the pump started having problems which burnt the motor which ended up taking out the ECU (remember, I did not have enough voltage on the ECU "towers" to energize my headlamp (voltage drawing test light)).

Lesson learned: The next time I run into this situation with a factory installed HCU (this one was from an 06), I'm going to bite the bullet and install the whole works right away. The 5-6 year range seems to be the lifespan of these systems, from my experience. I hope this information might help out the next guy.

Also, I don't know enough German to know how to order the pump motors directly from the manufacturer and that wouldn't have fixed the underlying problem anyway!
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Bus Tech II
Senior Member

108 Posts

Posted - 11/19/2013 :  04:45:54 AM  Show Profile  Visit Bus Tech II's Homepage  Reply with Quote
We have replaced several of these units and unfortunately we usually end up purchasing the whole thing. They are very expensive but the way I look at it is does safety of children have a price tag?? They can be hard to diagnose. The codes that seem to be right on the money are the pressure gradient codes which means pump failure, But I would have to agree with you in replacing the whole unit.
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mastertech
Advanced Member

242 Posts

Posted - 11/19/2013 :  9:21:24 PM  Show Profile  Visit mastertech's Homepage  Reply with Quote
You can kind of tell when the motors are starting to go . One might take a bit longer to shut off than the other and they will make a slightly different noise. As far as replacing the whole unit instead of just the hydraulic part Id give the nod to the whole thing. I am seeing more and more intermittant "ghost codes" like low amplitude and air gap to large when detailed testing and parts replacement shows no real defect. I am beggining to think the ecu's are failing electrically causing these codes.
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earl1412
Active Member

27 Posts

Posted - 01/07/2014 :  7:18:44 PM  Show Profile  Visit earl1412's Homepage  Reply with Quote
quote:
Originally posted by Dvorak

I have a bad ECU on a Wabco full power brake system (12v coming into it but no voltage going to one of the motors on the back side). My question is this: Have bad motors been burning out the ECU's and if so, should I be replacing the entire HCU? I'd hate to install a new computer only to have it burn out right away. Also, I've searched the previous posts but I've been unable to locate a part number to replace the pump motors. Has anyone found anything on these? Thanks in advance.


I have found a site for part numbers needed for motor/pump replacements only here it is
http://www.meritorwabco.com/MeritorWABCO_document/TP1349.pdf
This pdf shows what is needed to get correct parts for replacements due to age or code numbers found on various HPB units.
Good Luck!
earl
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