In The Shop: ABS Modulator Failure

One increasingly common issue that Harley Davidson owners have been facing is ABS module and modulator failure. Dot 4 brake fluid will absorb moisture over time. If your Harley is stored outdoors or in a humid environment, contamination of the fluid may happen even sooner. The moisture will eventually contaminate the internals of the ABS modulator. When this occurs, the front or rear brake lever becomes rock hard and actual brake function is nonexistent.

There are countless vehicles on the road, other than Harley Davidson, that utilize ABS systems and Dot 4 brake fluid. It is unsettling to us why Harley Davidson is, seemingly, the only vehicle manufacturer failing in this area. We realize that Dot 4 attracts moisture, but what is the engineering flaw that allows moisture to breach the sealed brake system? If you think about it for a minute, the answer is in a flawed brake modulator design. Harley was using Dot 4 in their brake systems, without issue, for years before Harley ABS models were produced and released to the public. When ABS was added, a module and modulator were added.

Harley ABS

The Harley ABS modulator is the only added component to the physical, working, ABS braking system (also added electrical: ABS sensor & module, and a magnetic wheel bearing). Being that the modulator is the only added component in contact with the brake fluid, it has to be the culprit. Rather than issue a recall, Harley’s solution to this issue was to send out a mass mailing to owners.

The letter stresses that owners have their brake fluid changed right away if it has not been changed within the last two years. Then, the fluid needs to be changed every two years after. The kicker, of course, is that the brake system can only be correctly bled with the dealership’s Digital Technician (or at a shop that has the Centurion Super Pro software – or the Twin Tec software).

Related Video: Bleeding ABS Brakes

Old Unit vs New Unit


A Disappointment from the American Company that We Love

If HD has not yet engineered and manufactured a correct Harley ABS modulator to replace the failing unit, it might be good business to change brake fluid for free until a recall can be issued and a replacement unit can be installed. That is, obviously, just our opinion. All that being said; we’ve been increasingly busy repairing this ABS issue. We have empty oil cases, with bad ABS modulators spilling out of the tops.


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46 Responses to “In The Shop: ABS Modulator Failure”

  1. Ronnie n britt

    just replace two front brake pads couple weeks AGO Road Street GALDY to work working nights moring when gain from going from myABS came so i went buy brackbleeder kit got back home took all the brack fiud out replace with new brake fiued it slow a cod litter y what i did to due

  2. Murad madhoun

    Hi, I just got a 2008 HD Electra Glide Classic ! Front and Back breaks sound working perfectly ! got to run a safety where ABS light on , there for safety failed due to non functioning of ABS module part number 40688-08 as I was told by HD dealer in that diagnosed been carried and ABS fuse was out by previous owner and they put it back , but unfortunately because of the ABS module the rear brake become so hard and not functions at all following diagnoses that been carried ! Also noticed when I press on the rear brake I can hear the click from the rear solenoid valve ! My question how I can test if the ABS module is operating (opens) While the bike stand ! Is the click sound means it’s opening and maybe air in side the system? Therefore , the brainiac so hard? Appreciate your advise . Because I end baying $440 just for new rear pads and front brake fluid change . Thx.

  3. NIKOLAOS GARNAVOS

    I need to buy a ABS UNIT I need to buy a ABS unit I need to buy an ABS unit(including the tubes) of Harley Road King model 2008 engine number 5HD1FR4488Y64X100, new or used.Can you inform me PLS? 9 OF HARLEY ROAD KING MODEL 2008

  4. Bob Marioni

    I bought my 2012 Street Glide with a service plan that did all the schedule maintenance at no cost, actually its paid up front, but still, I brought my bike to be services at all the increments. I did ask them to change the brae fluid 3 times and they upcharged me, but said they did it. 4 years ago I was riding at 40 mph and down shifted to a traffic light. As I approached the stopped cars, BOTH my front and rear lever and pedal locked up. I could not squeeze them and had no brakes at all. Luckily I veered off, jumped the curb, and came to a stop on the lawn of a gas station. I took my bike to Harley of West Palm Beach and they showed no concern for my situation. They said I neglected my brake fluid, when in fact the service dept said they changed it every two years. The service writer laughed and said "Well buddy, it's going to cost you $1500 or so to replace the modulator and cables!" I told him to F himself and said I would never spend a dollar at that service dept again. I went to a shop and had the ABS removed and regular cables installed. I've been riding for 48 years without ABS, and although I think a proper working well designed ABS is great, I can ride without it. Now that I've decided at 65, this is my last bike, should I reinstall the crappy system with new parts?

  5. Clifton VanDerveer

    2015 HD FreeWheeler rear brake failure/no peddle. Have bled the system twice. Still NO rear pedal response. Is there a way to replace/repair the ABS modulated without going to a HD dealer?

  6. George Baker

    Can the system be flushed out completely on the ABS the old modular The Harley's crazy what all is money it's money to repair one and all they do is flush them out and all they do is flush a mat and they don't put a new 1 on So what can I do to get I do to get my fix can I fix it myself can I fix it myself where can I go buy me a unit

  7. Mike

    Can I bypass my abs to avoid all these problems ?

  8. Daniel Reid

    has anybody had the ABS system false activate after replacing front rotors and pads I have a 2014 ultra classic that has false activations even after replacing the front wheel bearings and bleeding the system but no abs light comes on while riding?

  9. duwayne fiers

    Whats the best way to disable ABS so I can get home??Rear brake failed.

  10. duwayne fiers

    If I remove the ABS fuse ,,will I be able to get home?? Rear brake was failed as discribed ,but just want to make sure I could just temporarly bypass it??