ABS board / Module location on my 2001 H/R Ambassador 38PDB

[Boyd B.]

I am driving myself crazy trying to locate the ABS Board / Module on this motorhome. It is new to me and I like to have things working the way they were designed. All that being said the ABS light is always on. I finally got my hands on a decent schematic. But it does not show location of components. It is not in the Left front electrical compartment, nor  is it back by the inverter. It is also not under the dash or (that I could see) in the engine bay. I know what it should look like and cannot imagine an open board like it being left out in the weather underneath the coach. Any help would be greatly appreciated!

Boyd B.

2001 H/R Ambassador 38PDB

[jacwjames]

Do  you know what chassis you have?

[Ivan K]

Are you looking for the actual brain of it or the diagnostic trigger button? My button is left under the steering wheel but the actual box is in a ceiling of one of the basement compartments. I found its location from wiring bundle diagram.

[DavidL]

I assume like most abs systems there are diagnostic trouble code DTC diagnosis.  Get a scan tool.  You will take so much time looking at every wire when it more likely is a sensor.  The DTC will tell you in which circuit the system is unhappy and focus your efforts.

[Reka52]

On my 01 diplomat it in the front bay box under driver seat and is down low near the windshield washer tank it is about 4” square 

[Boyd B.]

The chassis is a Roadmaster Dynastar. It definitely is not in the left front electrical bay.  No buttons of any type under or round the steering wheel. The only electrical found in the storage bays are lights and slide motors. Other forums say the DTC button is part of the Board / Module. And that the button has a notoriously weak spring that can cause the light to stay on.

Just now, Boyd B. said:

Here is what I believe it looks like:

 

Edited August 2 by Boyd B.

[Ivan K]

The diagnostics button could look like in your picture or it could be like in this pic

[Russ R]

That is the board that I have. On my Windsor it is in the front run bay. It is mounted down low on the left side wall. It is hard to see because the wire bundle runs over the top of it. I have replaced the rest button and it worked temporarily. The board is obsolete but can be rebuilt.

Edited August 2 by Russ R

[Boyd B.]

15 minutes ago, Ivan K said:

The diagnostics button could look like in your picture or it could be like in this pic

My unit doesn't have any Diagnostic ports in or around the dash board. Only found one on the engine. Thanking everyone for the input!

17 minutes ago, Russ R said:

That is the board that I have. On my Windsor it is in the front run bay. It is mounted down low on the left side wall. It is hard to see because the wire bundle runs over the top of it. I have replaced the rest button and it worked temporarily. The board is obsolete but can be rebuilt.

This Board is what I believe the unit has. It is definitely not in the L/F electrical bay though... Thanks  for the input. I am sure I am not the only one that has every come up against this in a  "Snow Flake" build. You know, they all can look the same but none are built the same way. I read this on another forum and the more I work on this the more I see what they mean.

[PeterSchweizer]

On my 04 Cayman there is a 4" x 4" black box labled Monaco 4 with several ABS fuses in it. It is located in the battery bay passenger side behind the rear wheels. The ABS light always stayed on the 10 amp fuse in that box keep blowing which caused the light to come on. Traced it to a  2 chafed wires that where shorting out against each other . Possibly from a blown tire damaging the wire bundle - by prev owners as the battery compartment showed evidance of repaired damage. It was FUN tracing it!

[jacwjames]

Your manual specifies a Hydo-max braking system, but it does not provide a method to retrieve fault codes like most of the manuals do. 

Here is a link from IRV2 that has posts with several documents, not sure they'll help you solve your problem though.  https://www.irv2.com/forums/f115/hydro-max-wiring-and-brake-lights-332792.html .  One of the posters commented that he didn't have a module.

Do you have a wiring diagram, it might help, couldn't hurt. 

[Boyd B.]

2 hours ago, jacwjames said:

Your manual specifies a Hydo-max braking system, but it does not provide a method to retrieve fault codes like most of the manuals do. 

Here is a link from IRV2 that has posts with several documents, not sure they'll help you solve your problem though.  https://www.irv2.com/forums/f115/hydro-max-wiring-and-brake-lights-332792.html .  One of the posters commented that he didn't have a module.

Do you have a wiring diagram, it might help, couldn't hurt. 

Thanks for the link. Yes, REV was able to supply me with a good Schematic, but this doesn't supply location of the ABS ECU. I attached this schematic for anyone that needs it.

2000-2001 Kni Amb 38000517 chassis 12V.pdf

Edited August 2 by Boyd B.

[jacwjames]

Wonder if there is a way to use one of the ABS wheel sensors and use a wire tracer and trace it back to the module? 

[Boyd B.]

11 hours ago, jacwjames said:

Wonder if there is a way to use one of the ABS wheel sensors and use a wire tracer and trace it back to the module? 

Might be tough to do, but may have to try. Box 4 has a couple relays and fuses for the ABS circuit, the ABS blink code, ABS light, ABS Pump. The Blink Code fuse  (in Bx 4) blows as soon as the ignition is turned on. I am now going to pull all the fuses and relays related to the ABS until the light goes out. then one by one put them back in and see what part of the circuit should be blowing the fuse. Or I could put a solid wire in place of the fuse and then look for the smoke....

Edited August 3 by Boyd B.

[Boyd B.]

21 hours ago, PeterSchweizer said:

On my 04 Cayman there is a 4" x 4" black box labled Monaco 4 with several ABS fuses in it. It is located in the battery bay passenger side behind the rear wheels. The ABS light always stayed on the 10 amp fuse in that box keep blowing which caused the light to come on. Traced it to a  2 chafed wires that where shorting out against each other . Possibly from a blown tire damaging the wire bundle - by prev owners as the battery compartment showed evidence of repaired damage. It was FUN tracing it!

Thank you, Sounds like we may have the same wiring. This will at least give me direction. Now I will go at it one wheel at a time! This gives me a glimmer of hope, and possibly a lot more work.. But Thank you very much for taking a few minutes to post this info! I will post my findings.. Still I would like to find this phantom board that people speak of and schematic concur.

 

[PeterSchweizer]

30 minutes ago, Boyd B. said:

Thank you, Sounds like we may have the same wiring. This will at least give me direction. Now I will go at it one wheel at a time! This gives me a glimmer of hope, and possibly a lot more work.. But Thank you very much for taking a few minutes to post this info! I will post my findings.. Still I would like to find this phantom board that people speak of and schematic concur.

 

In the sites Files there should be a cayman, HR... wiring diagrams that I down loaded several years ago.