Is It Possible to Bench Test A 4WABS HCU?

BentSpurs

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I have a salvage 4WABS HCU to install in our ‘96 Bronco EB that the ABS warning light has been on for a few months. Is there a procedure for bench testing it before installation?
Thanks!
 

miesk5

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Yo Bent,
4WABS Hydraulic Control Unit (HCU) & Valves Wiring Diagram & Overview; "...The front inlet valves should read 5-8 Ohms each; all other valves should read 3-6 Ohms each. Sensors should read 800-1400 Ohms across the pins, and more than 10 Ohms from the metal shell to either pin. The pump motor sensor should be 5-40 Ohms. The acceleration sensor is a group of switches which should be closed when the truck is stationary & level. When the sensor is tilted ~1" up in the rear, pins 2-3 should go open; when tilted ~1.5" up in the front, pins 1-3 should go open..."; miesk5 Note; for all Resistance tests, battery needs to be disconnected; remove Negative cable at battery.
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BentSpurs

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Yo Bent,
4WABS Hydraulic Control Unit (HCU) & Valves Wiring Diagram & Overview; "...The front inlet valves should read 5-8 Ohms each; all other valves should read 3-6 Ohms each. Sensors should read 800-1400 Ohms across the pins, and more than 10 Ohms from the metal shell to either pin. The pump motor sensor should be 5-40 Ohms. The acceleration sensor is a group of switches which should be closed when the truck is stationary & level. When the sensor is tilted ~1" up in the rear, pins 2-3 should go open; when tilted ~1.5" up in the front, pins 1-3 should go open..."; miesk5 Note; for all Resistance tests, battery needs to be disconnected; remove Negative cable at battery.
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Miesk5,
Many thanks for the quick and comprehensive reply but seeing you’re Navy, I shouldn’t be surprised. Dad was an Aviation Machinst Mate, 1942-45 U.S.S. Cleveland CL-55.
Skal!
 

paul rondelli

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Bent

If you could do a detailed write up of the repair ... I would be greatful... my ABS light has also just came on. I'm on the fence about just getting a porportioning vlaue and bypassing the whole ABS system.
 

BentSpurs

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Update: 4WABS HCU from a salvage yard arrived. Luckily had a master mechanic friend who bench tested it. Fail, open circuit.
So what year, model Explorers have compatible ones?
Thanks!
 

miesk5

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Bent

If you could do a detailed write up of the repair ... I would be greatful... my ABS light has also just came on. I'm on the fence about just getting a porportioning vlaue and bypassing the whole ABS system.
Yo Paul,
I didn't see this post until now. Second time O'Day that this has occurred!

What year is this for"?

Post this question in a new thread so that I can find it again.
For now;
4WABS Control Module Bypass for PSOM Operation due to Bad 4WABS Control Module at 4WABS Module Connector; "...jumper 14 (CKT 530, LG/Y)to 21 (CKT 519 (LG/BK) & 39 (CKT 491 (O/LB)to 22 (CKT 523, R/PK)..."
Source: by Turbo Ghost at FSB
 

miesk5

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Update: 4WABS HCU from a salvage yard arrived. Luckily had a master mechanic friend who bench tested it. Fail, open circuit.
So what year, model Explorers have compatible ones?
Thanks!
Yo B,
There have been a few threads on the site that discuss swapping an Explorer ABS hydraulic control unit into the Broncos with 4WABS. The recommendation was to use the HCU out of a 93-94. The only modification required is to modify the harness between the HCU and the control module. The connector is the same but it is reversed (male is female on the Explorer) and the isolate and dump valve pins are reversed on the harness. The previous write ups were helpful and I thought I could add to the knowledge base by adding some pictures and details on doing the swap.
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You can note some of the differences here. The Bronco HCU is on the left, the Explorer unit is on the right. The part numbers are F3TZ-2C215-B (Bronco) and the F3TZ-2C215-A (Explorer). I sourced the NOS Explorer unit on eBay from Spark Surplus out of Sugarland, Texas. I was happy with the price and it was well protected for shipping.
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The C121 connector between the HCU and control module from the Bronco is on the left (male pins), the Explorer on the right (female pins). If you want to remove the pins you will need to pull the red clip that holds them in place using a small needle nose pliers. You can also push the clip from the back side with a small nail when you back out the rubber wire seal. Pin number 1 is top right, pin 5 is bottom right for both connectors. You can transfer the Bronco connector by splicing the wires or you can source the correct male pins. I chose to splice the harness because I’m impatient and didn’t know where to get the pins.

I verified the resistance on all of the valves before I started cutting. I also labeled all of the Explorer leads prior to cutting.
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A4 MEASURE VALVE RESISTANCE AT ANTI-LOCK HYDRAULIC CONTROL UNIT
Disconnect the 8-pin connector from the anti-lock hydraulic control unit.
Measure resistance between the following on the COMPONENT side of the 8-pin connector:
Pin 1, Pin 4 and Pin 2 (rear axle outlet)
Pin 1, Pin 4 and Pin 3 (rear axle inlet)
Pin 1, Pin 4 and Pin 5 (front right inlet)
Pin 1, Pin 4 and Pin 6 (front left outlet)
Pin 1, Pin 4 and Pin 7 (front left inlet)
Pin 1, Pin 4 and Pin 8 (front right outlet)
NOTE: Refer to the system schematic for anti-lock hydraulic control unit pin designations.
All inlet valves should be 5-8 ohms.
All outlet valves should be 3-6 ohms.

Details on troubleshooting the Bronco HCU can be found in the following thread. My unit had infinite resistance on the rear dump pin 3.
ABS Code 17

I used the following thread to test the Explorer HCU and confirm how to map out the pins to the Bronco.
1993-1996 4WABS trouble codes WITH troubleshooting guide!

Long story short, you will need to reverse pins 2&3, 5&6, and 7&8 on the Explorer harness to match the Bronco wiring.
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Here is the harness after splicing which I protected with heat shrink tubing and plastic loom cover. It's a good idea to have the ABS wiring diagram handy when doing all of this. When you are done recheck that the resistance maps out properly. Then you are ready to install it in your Bronco.

After I installed the HCU I bled my brakes and started it up. No more ABS light! I did a quick test drive and the brakes felt great. I am going to find a dirt road tomorrow to do a few hard stops to cycle the HCU. Depending on how it goes I may also do the 'ghetto' bleed procedure linked below.

Ghetto 4WABS HCU Bleed Procedure
By Idahorocks

"A pump from an Explorer will work. Its wiring harness is reverse from the Bronco. You can cut off the Bronco harness and solder it to the Explorer pump. I had to do this several months ago and it's worked fine. Those HCUs are much easier to find than the Bronco one. I bought a NOS one on ebay for ~$150 which was cheaper than a reman."
BY ?
 

BentSpurs

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Thanks very much Miesk5. I've sourced a '94 Explorer 4WABS unit so we shall see if it bench tests before doing the Franken-pump surgery. BTW, have you ever heard of anyone rebuilding one of these? Some old school starter rebuilders should have the skills.
Cheers!
Bent
 

Tiha

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I looked into it. My problem was never the main DC motor though. I was having problems with the solenoids.

So if your old one is just a bad motor, pretty good chances of repairing it.

Once you get into solenoids, then you have to deal with pistons and seals. Much harder to find if not impossible.
 

miesk5

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Thanks very much Miesk5. I've sourced a '94 Explorer 4WABS unit so we shall see if it bench tests before doing the Franken-pump surgery. BTW, have you ever heard of anyone rebuilding one of these? Some old school starter rebuilders should have the skills.
Cheers!
Bent
Yo,
Last year I checked Cardone on line catalog and they showed it as available.
I then checked Rock Auto and they list 122025, but describe it as "w/Rear Wheel ABS Only" .
I called a Navy pal who works at Cardone and asked him about 122025.
He confirmed with his technical group that 12-2025 is for JUST Rear Wheel ABS, NOT 4WABS.

NEXT UP TO BAT is BBA which was WELL-REGARDED for their remanufactured 4WABS control modules and HCUs. http://www.bba-reman.com/us/catalogue/parts/84/
Following from August 2020;
4WABS Hydraulic Control Unit (HCU) Sources "...Used price locally is $150.00; 60 day guarantee; Babaganoosh wrote; "...BBA did the rebuilds on ABS Modules for my old VW/Audi Shop. They were super inexpensive, fast, friendly, and only had one issue with them ever and it was 50% my fault anyways (keep in mind it's VW stuff anyways...". by consensus the best re man 4WABS Hydraulic Control Unit (HCU)s are from bba-reman.com; BBA quotes $200 plus shipping for repair of/my HCU; "It usually takes about 3 days from receipt to repair..."
miesk5 UPDATE, check w/BBA first; they may have stopped re-man ops.
 

BentSpurs

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Yo,
Last year I checked Cardone on line catalog and they showed it as available.
I then checked Rock Auto and they list 122025, but describe it as "w/Rear Wheel ABS Only" .
I called a Navy pal who works at Cardone and asked him about 122025.
He confirmed with his technical group that 12-2025 is for JUST Rear Wheel ABS, NOT 4WABS.

NEXT UP TO BAT is BBA which was WELL-REGARDED for their remanufactured 4WABS control modules and HCUs. http://www.bba-reman.com/us/catalogue/parts/84/
Following from August 2020;
4WABS Hydraulic Control Unit (HCU) Sources "...Used price locally is $150.00; 60 day guarantee; Babaganoosh wrote; "...BBA did the rebuilds on ABS Modules for my old VW/Audi Shop. They were super inexpensive, fast, friendly, and only had one issue with them ever and it was 50% my fault anyways (keep in mind it's VW stuff anyways...". by consensus the best re man 4WABS Hydraulic Control Unit (HCU)s are from bba-reman.com; BBA quotes $200 plus shipping for repair of/my HCU; "It usually takes about 3 days from receipt to repair..."
miesk5 UPDATE, check w/BBA first; they may have stopped re-man ops.
Tiha's comment above gave me pause re prospects for rebuilding or at least for a reasonable amount of money vs other routes. I'm fairly certain that BBA has tubed based on recent comments I was seeing from owner's who'd sent units for rebuild and having no luck getting anyone at BBA on the phone or to reply to emails. Too bad, they were doing well but apparently went into receivership, aka O thank heaven for Chapter 11 (or 7). It mystifies me as to why no one is making a 4WABS HCU given millions of F-series not to mention Broncos as a ready market especially in today's world where more and more of them are being restored. Now where did I put that phone number for Warren Buffett? Thanks!
 
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miesk5

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Tiha's comment above gave me pause re prospects for rebuilding or at least for a reasonable amount of money vs other routes. I'm fairly certain that BBA has tubed based on recent comments I was seeing from owner's who'd sent units for rebuild and having no luck getting anyone at BBA on the phone or to reply to emails. Too bad, they were doing well but apparently went into receivership, aka O thank heaven for Chapter 11 (or 7). It mystifies me as to why no one is making a 4WABS HCU given millions of F-series not to mention Broncos as a ready market especially in today's world where more and more of them are being restored. Now where did I put that phone number for Warren Buffett? Thanks!
Yo, try this Google search:
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BentSpurs

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Was just about to pack up and ship the nonfx 4WABS back to the junk yard for swap to Explorer and thought, WTH one last try at an online search for repair, rebuild services and had a few hits but after I'd call to discuss, would find they only worked on the electronic modules, not anything hydraulic. Then stumbled upon "ECU Testing" (Heanor, UK) who it appeared actually work on HCU units so I called them and spoke w "David" who in his proper accent assured me that while they hadn't rebuilt my exact part (their website shows they have done a variety of Ford model parts), it sounded doable and to send it and pointed me to their webpage w the "Test Form" where I could submit all the pertinent details and it would generate my DHL shipping label. And it did without so much as a credit card. They'll bill me when the rebuild is complete, around $50 shipping and between $230-270 for the rebuild which is 2-3 days turnaround. Dropped it off at a DHL location today. Granted, this is as much an experiment to see if this is as a legit service as their FB reviews would indicate but that is the latest. Stay tuned.
 

miesk5

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Was just about to pack up and ship the nonfx 4WABS back to the junk yard for swap to Explorer and thought, WTH one last try at an online search for repair, rebuild services and had a few hits but after I'd call to discuss, would find they only worked on the electronic modules, not anything hydraulic. Then stumbled upon "ECU Testing" (Heanor, UK) who it appeared actually work on HCU units so I called them and spoke w "David" who in his proper accent assured me that while they hadn't rebuilt my exact part (their website shows they have done a variety of Ford model parts), it sounded doable and to send it and pointed me to their webpage w the "Test Form" where I could submit all the pertinent details and it would generate my DHL shipping label. And it did without so much as a credit card. They'll bill me when the rebuild is complete, around $50 shipping and between $230-270 for the rebuild which is 2-3 days turnaround. Dropped it off at a DHL location today. Granted, this is as much an experiment to see if this is as a legit service as their FB reviews would indicate but that is the latest. Stay tuned.
Yo,
Great!
Am Tuned and hopeful!
 

BentSpurs

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UPDATE: ECU Testing examined the HCU and deemed it irreparable due to condition of the solenoids and shipped it back to me. I’ll be returning it to the salvage yard for swap w another one that hopefully is a functional one. Meantime I bought two more (they say persistence pays but that could be read a couple of ways), one arrived in miserable condition w the motor casing “shedding” paint w metal. Another was by luck when I contacted an owner parting out a ‘96 with only 60k miles that had been in an accident, to inquire about a rear bumper. Picked up both the bumper and HCU yesterday and the HCU looks like new and he included the lines to/and the brake fluid reservoir. Next is getting it installed. Is there a special tool required for bleeding these units? Thanks!
 

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