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SAMRO S338RJ Curtain Trailer (2002) - Pneumatic Brake System Fault: Disc Brakes, ROR Axles, ABS

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  • #1 16730099
    dimk1
    Level 10  
    Posts: 47
    Rate: 28
    Hello,
    I have a problem with the SAMRO curtain model S338RJ. Born in 2002. Disc brakes. Axes ror. ABS.
    The problem is that the trailer does not get the right pressure or no air on the brakes. They are all tightened and there is no reaction to the manual or working brake with the tractor attached, and also to the valve unfastened with air.
    The first suspicions are on the unresponsive parking and release valve on the trailer, or on the brakes quick release valves.
    The semi-trailer was not used for a long time before, everything was fine. Recently, the discs, pads, regenerated calipers, one brake cylinder and a brake valve / regulator were replaced.

    Maybe someone had a similar case and will tell you. I will be grateful! :)
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  • #2 16730986
    darfur5
    Level 35  
    Posts: 2110
    Help: 266
    Rate: 1695
    Check the slot filters on the trailer hoses, they should be installed behind the connectors (yellow and red), some trailer models are not used. Check the directional valves between the air cylinders.
  • #3 16731500
    stanisławpiotr
    Level 33  
    Posts: 1539
    Help: 209
    Rate: 819
    It would be advisable for you to specify what brake system the trailer has. Wabco, Knorr-Bremse, Haldex or a photo of the valve and the number of the park-release valve.
  • #4 16733868
    dimk1
    Level 10  
    Posts: 47
    Rate: 28
    Haldex brake system. Park-release valve replaced today. Works but still no response at the brake cylinders.
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  • #5 16733884
    Hektar Zahler
    Level 34  
    Posts: 2333
    Help: 230
    Rate: 526
    Is the departure protection working?
  • #6 16733898
    dimk1
    Level 10  
    Posts: 47
    Rate: 28
    Did not work. The brakes do not react to anything.
  • #7 16733944
    Hektar Zahler
    Level 34  
    Posts: 2333
    Help: 230
    Rate: 526
    This is interesting. It is necessary to disconnect the modulator output and at least eliminate its fault. The valve is supposed to block the brakes below a 3.5 bar drop on the tractor power from what I remember. I'm going to find out which one it is. Or you've got the wrong leads my friend.
  • #8 16733999
    dimk1
    Level 10  
    Posts: 47
    Rate: 28
    Nobody messed up 90% of the cables, because the previous owner simply neglected it. It looks like something is blocking her. A moment earlier, there was also a problem with lifting pillows, but here the situation has improved and it is ok.
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  • #9 16734068
    Hektar Zahler
    Level 34  
    Posts: 2333
    Help: 230
    Rate: 526
    The 21 TrCM + output enters modulator 4. The control is to be on disconnected power supply and full pressure in the trailer, or with the brake pedal pressed. Rather, the 10% you have wrong outputs, because how can the protection not work like a new multivalve. Something is wrong. Or someone has already fought hard with what he mixed up.
  • #10 16738094
    saron22
    Trucks specialist  
    Posts: 2885
    Help: 308
    Rate: 1595
    There is air in all cylinders ??
  • #11 16738989
    stanisławpiotr
    Level 33  
    Posts: 1539
    Help: 209
    Rate: 819
    My colleague, you have still not specified which park-relief valve you have replaced. In the appendix I give you two types produced by Haldex, one of them shows the installation diagram. Check that you have a properly connected valve.
    Attachments:
    • zawór hamulca trcm .pdf (2.7 MB) You must be logged in to download this attachment.
    • zawór hamulca trcm.pdf (851.91 KB) You must be logged in to download this attachment.
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  • #13 16743196
    stanisławpiotr
    Level 33  
    Posts: 1539
    Help: 209
    Rate: 819
    What's your ABS valve? Below is the installation diagram for eb + II.
    Attachments:
    • SAMRO S338RJ Curtain Trailer (2002) - Pneumatic Brake System Fault: Disc Brakes, ROR Axles, ABS instalacja zaworu postojawego.png (257.76 KB) You must be logged in to download this attachment.
  • #15 16746774
    stanisławpiotr
    Level 33  
    Posts: 1539
    Help: 209
    Rate: 819
    So it is ABS MODULAR. Below is a diagram of the pneumatic installation. The second is diagnostics manual electrical diagram SERVICE MANUAL ang.
    Attachments:
    • MODULAR instalacja.pdf (17.22 MB) You must be logged in to download this attachment.
    • MODULAR schemat diag manual.pdf (1.94 MB) You must be logged in to download this attachment.
  • #16 16759118
    dimk1
    Level 10  
    Posts: 47
    Rate: 28
    Thank you very much for the sent diagram! It turned out that the yellow and red wires were swapped. Everything is already working ;)
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Topic summary

✨ The discussion revolves around a pneumatic brake system fault in a 2002 SAMRO S338RJ curtain trailer equipped with disc brakes, ROR axles, and an ABS system. The user reports that the trailer's brakes are unresponsive despite recent replacements of various components, including calipers and a brake valve. Responses suggest checking the slot filters on trailer hoses, directional valves, and ensuring correct connections of the park-release and ABS valves. The user later identifies that swapped yellow and red wires were the cause of the issue, which has since been resolved.
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FAQ

TL;DR: No-brake on a 2002 SAMRO S338RJ with Haldex was traced to misrouted air lines; departure protection locks below 3.5 bar—“you’ve got the wrong outputs.” [Elektroda, Hektar Zahler, post #16734068]

Why it matters: This FAQ helps techs quickly diagnose zero-response disc brakes on ROR-axle trailers with Haldex ABS/park-release systems.

Quick Facts

How do I fix a SAMRO S338RJ trailer that has no brake reaction at the cylinders?

Start at the connectors. Verify correct red (supply) and yellow (control) line routing. The thread’s root cause was swapped lines; correcting them restored braking. Then confirm the park-release valve is plumbed per Haldex 700034 and that air reaches the modulator inlet. Finally, check quick-release and directional valves for blockage. “Wrong outputs” will keep the protection active and prevent response. [Elektroda, dimk1, post #16759118]

What symptoms did the owner observe before the fix?

All brakes stayed applied and did not react to manual or service braking, even with the tractor or an external air source. Earlier, there was also an issue lifting the air suspension bags, which later cleared. These symptoms pointed to an upstream air routing or control fault rather than seized calipers. [Elektroda, dimk1, post #16730099]

Which brake system brand is on this trailer?

Haldex. The owner confirmed a Haldex brake system, replaced the park‑release valve with a Haldex 700034 unit, and identified a Haldex 020122 ABS modulator. Matching parts and diagrams to Haldex simplified troubleshooting and ensured correct port mapping. [Elektroda, dimk1, post #16733868]

What is a park‑release valve and why does it matter here?

The park‑release (multivalve) manages parking brake application/release and interfaces with supply and control lines. If misconnected, it can hold the brakes on or block service-brake actuation. Verifying the exact Haldex model and following its installation diagram is crucial after replacement. [Elektroda, stanisławpiotr, post #16738989]

How does the Haldex departure-protection feature behave?

It blocks brake actuation when tractor supply drops below about 3.5 bar to prevent unsafe departure. If supply/control lines are misrouted, the system may “think” pressure is insufficient and keep brakes unresponsive. “The valve is supposed to block the brakes below a 3.5 bar drop.” [Elektroda, Hektar Zahler, post #16733944]

What is the Haldex Modular ABS (020122) on this trailer?

It’s a pneumatic-electronic modulator that meters air to the brake chambers under ABS control. The identified unit is the Haldex 020122 Modular ABS modulator. Correct inlet/outlet connections are essential; misrouted lines will stop any brake response regardless of electronics. [Elektroda, dimk1, post #16746503]

Could clogged filters or valves cause zero brake response?

Yes. Slot filters behind the red/yellow connectors and directional valves between cylinders can clog, restricting air. Inspect and clean them if pressure at the connectors is correct but chambers remain inactive. This is a quick, low-cost check before deeper diagnostics. [Elektroda, darfur5, post #16730986]

What quick 3‑step diagnosis should I follow before replacing more parts?

  1. Verify supply/control pressures at the red/yellow suzies and confirm correct line routing.
  2. Confirm the park‑release valve ports match the Haldex diagram and supply reaches the modulator.
  3. If still no response, disconnect modulator outlet to isolate it and test control. [Elektroda, Hektar Zahler, post #16734068]

How was this specific case resolved in the thread?

By identifying that the red and yellow lines were swapped and correcting them. After fixing the routing, the trailer brakes began working normally again. This shows why line identification and port mapping should be your first checks on no‑response faults. [Elektroda, dimk1, post #16759118]

What is an ABS/EB+ system in trailers, in simple terms?

It’s an anti‑lock system that uses wheel sensors and a modulator to prevent wheel lock and manage brake pressure. In this thread, the installation diagram referenced EB+ II guidance, reinforcing that correct pneumatic routing is foundational to ABS function. [Elektroda, stanisławpiotr, post #16743196]

Why didn’t replacing the park‑release valve immediately fix the brakes?

Because the underlying issue was misrouted supply/control lines. Even a new multivalve cannot function if its ports receive the wrong signals. Always verify connections against the model’s diagram before assuming a component failure. [Elektroda, dimk1, post #16733868]

Is there an edge case where protection still won’t work after installing a new valve?

Yes. If outputs are wrong into the modulator, protection appears inoperative and brakes stay locked. As noted, miswired or misrouted lines can mimic a failed valve. “Something is wrong. Or someone … mixed up.” [Elektroda, Hektar Zahler, post #16734068]

What maintenance history might complicate diagnosis?

Recent replacements included discs, pads, regenerated calipers, one brake cylinder, and a brake valve/regulator. With many touched parts, routing mistakes become likely. Note the single cylinder replacement as a clue to uneven prior work. [Elektroda, dimk1, post #16730099]

Does the system react to manual or service braking when lines are swapped?

No. With swapped control/supply, there was no reaction to the hand control (trailer brake), service brake, or even with an external air valve connected. That consistent non‑response narrows faults to upstream routing or protection logic. [Elektroda, dimk1, post #16733898]

How can I verify modulator port mapping on this setup?

Follow the guidance: the TrCM output should feed the correct modulator port; incorrect routing stops any actuation. If unsure, disconnect the modulator output temporarily to test whether the modulator or the plumbing is at fault. [Elektroda, Hektar Zahler, post #16734068]

What should I check first if air suspension had issues too?

Check overall supply integrity and line routing. The thread noted a prior issue with lifting the air bags, which later cleared. Such symptoms suggest upstream air or control issues that can also affect braking response. [Elektroda, dimk1, post #16733999]
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