ABS Dash Light On and Noise

[EngineerMike]

I don't know. I read far enough into the ABS maintenance manual & the Vansco wire loom schematics to figure out the switch grounds pin18 on the ABS ECU (for some reason it also grounds pin05 on the rear Vansco 23 pin connector, the one that's shorter than the other 2, GKW that's doing).
Hopefully somebody with an ABS light will try it and report success or tell us how it really works.

Originally I thought the toggle was to put ABS diagnostic info to the 9-pin round gray diagnostic port, perhaps in lieu of something else. However the schematics show the reality, the ABS switch is totally separate & not involved in the diagnostic port at all, and any jive moho owner can read his/her blink codes while sipping a cold one.

[Hobdendw]

Thanks to ALL for the advice and support so far. I haven't yet had the time or appropriate weather to get any closer to resoution on this latest issue.
Will post again once I locate the ECU and do some testing. I also need to locate the relay that is mentioned on page 7 of the Class 5 to 7 Truck & Bus Hydraulic Brake System Diagnostic Guide that is in the Alpine Tech Library. I was aware of the ABS toggle switch behind the kick panel at the dash, thanks for the tip on how to use it for testing.

[EngineerMike]

David- the relay is located next to & above the Bosch HydroMax master cyliner/boost assembly on the "bellcrank" bracket iirc, behind the gen slide and within the upper front fiberglass cap portion that is below the windshield.
It has one fat white wire, one fat red, and either two skinnier whites or maybe its a skinny white & a skinny black. wires enter relay from the bottom. This whole thin isn't related to your ABS, its a separate system, and that relay powers the electrical boost pump for your power brakes when the key is off or when key is On but engine not running (or at least it should, 04's and 05's left factory not properly programmed for this funcion, and we have posted a work-around fix here and on ACA's Tech Library to correct that). You will notice similarity between the cylindrical motor housing on the Bosch & the black cylindrical motor housing on the ABS setup in your basement you photo'd above (also to the HWH pump motor for that matter). These all have a similar form factor.

[Hobdendw]

OK Here's my update on the ABS Module Pump that won't quit running unless I disconnect it. Hopefully my post(s) here will help someone else in the future if they have to troubleshoot this system. I have multiple pictures so I think I will do a series of posts on what I did to diagnose this problem. But first, I'll give you the solution that I found along with a little background, because I think an old adage applies here: "Always look at what was last repaired/replaced when diagnosing a new problem." It turns out that my ABS problem was the direct result of the starter going bad and its subsequent replacement along with both the starter solenoid and charging solenoid.

The bottom line is that I finally got the ABS module pump to stop running by switching the two small wires on the charging solenoid. They were apparently wired incorrectly when it was replaced in January by a small repair shop in Las Vegas NM.
The story on why it was replaced is as follows: We were returning to Colorado from Quartzsite in January and experienced hesitation when shifting, the Coach was starting to feel underpowered. I knew I should have replaced those fuel filters before the trip! It had been over a year since last serviced. Anyway, we saw a billboard along I25 for a Diesel truck repair shop so we pulled in to get a diagnosis. The shop put on two new fuel filters to fix my power problem and in doing so… the tech removed the starter for easier access to the spin-on small fuel filter that is just above the starter on the passenger side of the engine. When he put the starter back in and I started up the engine, the starter didn't disengage, it kept trying to crank the engine while it was running. Luckily, it disengaged itself after 30 seconds or so. It did this each time after several restart attempts. Therefore, the tech decided the problem must be the starter relay since he was sure the starter was wired back correctly… however, instead of replacing the starter relay he incorrectly replaced the charging relay (which looked the same) and is located at the back of the battery compartment. Of course, this didn't fix the starter problem. I called Engineer Mike for advice and he quickly determined they had replaced the wrong solenoid, I told the tech this but they didn't have another one on hand, so after another start attempt when the starter successfully disengaged after several "breath-holding" seconds of hang time, I told him to leave it. It was getting late and I would drive the rest of the way home without shutting the engine down.
When I did get home safely in the driveway, I shut down the engine and tried to do a restart, unfortunately it didn't heal itself So when the weather finally permitted here in Colorado, I pulled the starter and had it rebuilt locally (the shop said it had corrosion and the solenoid attached to the starter motor was fried). I also purchased and installed new solenoids as follows:
Starter solenoid Trombetta 974-1215-010-09 from Murcal.com for $18.95
Charging solenoid Trombetta "Bear" 114-1211-020 from Murcal.com for $48.95
Note: Thanks need to go out to Engineer Mike once again for the information on these.

Here's a picture of the new charging solenoid. Note that the two small wires on the bottom have been reversed. Doing this made my ABS module pump stop running continuously.

[Hobdendw]

Charging Solenoid: This picture didn't want to attach to the previous post, I had to resize it.

[Hobdendw]

I have tried three times now to load more pictures and give some of the steps that I took to troubleshoot the system to include how to use the ABS diagnostic switch… but I keep getting bumped off the internet. Therefore, I will try to post again tomorrow for those that might be interested. Please stand by.

[Koop]

Thanks Dave, for the info. I hope you can successfully add the photos tomorrow.

[Old Scout]

Interesting conclusion--I continue to marvel at the simplest explanations for the most complex [seamingly] problems --many of which self-inflicted. Since I still get an occasional ABS warning light on the dash and based on EMs input, I tried to induce a diagnostic mode by shorting one or more of the pins in the ABS plug--no joy. At the time I wasnt armed with my volt meter so the grounding process may require use of an external ground point. As mentioned earlier--this process works on my 87 Vette's ECM port but its a bit more "intimidating" to ground out the ABS on the coach.

[Hobdendw]

Alright, let's see if this morning is more conducive to getting some pictures loaded on this iRV2.com forum. It was taking a long time to upload photos yesterday evening. When a photo would finally load and I hit submit, I kept getting "Network Error" and lost my text as well as photo(s).

OK, first of all, hopefully this may help someone else in the future if the ABS light comes on. In my situation, the light on the dash came on and I also started to hear a louder than usual "whirring" noise that seemed to be coming from the Xantrex inverter/charger. I incorrectly assumed that the fan on the Xantrex was going bad. After a couple weeks, I finally investigated further by unplugging from shore power, turning both master switches off, and shutting down the Xantrex… the whirring noise was still there. I tracked it down to the ABS module pump which is located in the middle of the coach just forward of the rear tires. I had to crawl into the compartment to access it and at the time, the only way I found to make it stop was to disconnect the connector as shown in the picture here on this post (hopefully). Important to note is that the ABS module pump would run constantly (off the 2 chassis batteries)… even with all power and switches turned off.

[Hobdendw]

I finally got around to reading up on the system, the manual is available on the Alpine Coach Tech Library. I learned how to use the ABS diagnostic switch which is located behind the dash kick panel forward of the passenger seat. It is the toggle switch in the bottom right hand side of the attached picture:

[Hobdendw]

To perform the diagnostic test, you have to turn the ignition key to run, but don't start the engine. Wait for the dash chimes to stop and gauge needles to quit moving. Then flip the toggle switch to ON for approximately 1 second and then back of OFF. Then watch your dash for the ABS symbol to blink. Mine would blink 8 times consecutively, then after a two or three second pause, it would blink 2 more times consecutively. This blinking will continue until you turn the key off. The manual referenced earlier, says that a blink code of "8-2" means my problem is "Continuous supply to ECU with ignition off". The action to take is "Check for proper wiring connections. Make necessary repairs. If problem persists, replace ECU".
So, it was time to break out the wiring schematics:

[Hobdendw]

I then started to disconnect everything that was associated with the ABS system to see if I could get the pump to stop running. Of course I did this after plugging back in the connector on the ABS Module itself.

Here is a picture of the battery compartment where most of the system electrical components are located:

[Hobdendw]

First, I found the ABS ECU on the left hand upper side of the battery compartment (picture 1 below). I disconnected each of the 3 connectors, one at a time, and found out that when I unplugged the white connector on the right side, the pump would stop running and i heard a click from the black relay (picture 2 below).

[Hobdendw]

The picture of the black relay (above) has to be rotated clockwise for proper viewing.

I then found out that if I disconnected the black relay (after plugging the ECU back in of course) that the pump would also stop running. I then identified a fuse specifically for the ABS system (picture below). It is the silver fuse that looks like a mini USB stick. Wish I knew about that earlier because it's certainly the easiest method to get the pump to stop running when you pull it. I took the relay down to NAPA and got a replacement… ~$17.00, it didn't help, with new relay installed and everything plugged back in, the pump would continue to run and drain the chassis batteries.