ABS Brake Dash Light

[0533]

Paul, where did you purchase the Regulator and what did it cost?

[Jon Wehrenberg]

Bruce,

If your bus was putting out 28 volts when you did the test all you know is that both the regulator and the alternator were both working when you started the test. The time to do the test is when the chassis voltage drops down to 25 or 26 to indicate something is not working.

You seem to have an intermittent problem, somehow occuring after a period of time. When you notice the voltage drop thats when to run that test. You are almost free of concern because unless you run very heavy chassis loads, if your alternator or regulator stops functioning, you can run the generator plus turn on your chassis battery charger.

Paul had an intermittent problem and he also has a chassis battery charger so when his system finally failed to work he isolated the problem and cured it with a regulator. It could just as easily been a bad alternator, but until the system failed so the test could be preformed he could only speculate.

In the meantime just find a shop that can rebuild the alternator and locate sources for a new or repaired regulator so when the voltage drops again you can test and determine what has failed.

[0533]

Good morning Jon,

I tested the output under load, 1000 RPM's and with light, blower and air on, the Chassis voltage meter was fluctuating when I did the test. I think that the problem is always there, but gets worse as I was driving along, as time passed, I was draining down the chassis batteries or something???

I guess my question would be if I conducted the test you suggested and the voltage increased is the regulator not malfunctioning or not???

I plan on getting a regulator today and install it and do the test again.

While I was at Prevost they did suggest a few upgrades to my engine compartment. See following below:

1. Pulley tension upgrade kit that includes a change/move of the oil fill a tensioner and a new larger diameter oil line from the Alternator for increased flow/capacity. I was told by Prevost that the company that rebuilds the Alternators will not stand behind them unless the oil line upgrade (larger diameter) is installed. They also wanted me to have a separate ground strap installed from the Alternator to the chassis. They said that the buildup of scale/rust between the mount for the alternator develops scale and can cause a poor ground for the alternator.

[Jon Wehrenberg]

All the test with the jumper does is eliminate the regulator from the system. You in essence by-passed the regulator and as you saw you had an unregulated alternator output.

Having said that it is my opinion (nothing more than an opinion) that the belt tensioner is an unnecessary expense as long as the belt tension is adjusted properly. The oil line may be a good upgrade, but I don't know that for a fact. Being assured that the alternator has a good ground is critical.

Don't spend any money for an alternator or regulator until you have the alternator output stop. Then check the regulator / alternator as you did. But in the meantime remove one of trhe alternator bolts, make certain is is clean and totally free of scale and rust, not only on the bolt and nut, but on the surfaces it contacts and reinstall it. If the ground was in fact your problem that should solve it. I'm not sure it will solve your problem, but start with the cheap easy stuff.

[phorner]

Bruce,

Jon is 100% correct in that I waited until mine "failed" before performing the test on the regulator to confirm that the regulator was bad.

I also was having an intermittent low chassis battery voltage problem that would usually cure itself within 20 to 30 minutes of driving. I did not have the ABS light issue that you describe, just the battery light on the dash coming on and the voltage reading on the gauge.

So, when mine finally went, I performed the regulator jumper test as Jon described while the failure was present, which confirmed that I had a bad regulator. This test is only meaningful if performed while the low voltage problem is present.

I got my replacement voltage regulator from Advance Auto Electric in Port St. Lucie. Cost was around $200. They can also re-build your alternator if need be. Their number is 772-337-1280

[0533]

I think it is possible that mine is about to fail and decided to replace now and see if it makes the difference, process of elimination. I am no rocket scientist and might well have to replace everything before I figure out the real problem.

I received the new regulator today, it is a little different has five connections the first 4 are the same, Ground, Field, Battery, Ignition plus a 5th for Sense. Which makes non to me so I plan on forgetting this one.

The face is different as well, black poured in plastic material covering over the Mother board I guess as apposed to silver metal cover.

[phorner]

Bruce,

Sounds to me as if you may not have the correct regulator. Mine was an exact replacement.....

[0533]

I was told by Prevost that this was the replacement for the older style.It is model #19020413 MFG date is 2005 maybe it is not new but I paid $181 Big ones. I have just taken a closer look at this regulator and have noticed that it is a 12 Volt not 24 Volt regulator, my old one is a Delco Remy 24 Volt version, I think I need to call Prevost.

[0533]

I have had an ongoing problem with my dash ABS light coming on. It appears that when I had my over voltage issue it tripped the 12 volt circuit in the ABS module and kicked it off. When the light is on there is no ABS controlling the braking system on our buses, no matter what the actual problem is.

I had the ABS readout computer attached and it said that I had two issues, an ABS over voltage and a right rear drive axle sensor failure, or sensor wire connection failure.

The tech preformed a check of each sensor by activating a signal that would create a clicking sound at each sensor. All sensors answered the signal with a clicking sound, in other words they responded as though they were being activated under real world conditions.

This was done on Thursday afternoon. When I backed out of Bay #2, I decided to go for a spin down the road to see if the ABS dash light would go out after I exceeded 4 MPH it did not.

On Friday morning when we had the Bus up on the lift to inspect for air leaks, change out the Air system water filer cartridge and take a look at the Rear axle ABS sensors and do an electrical check directly on them to see if the voltage was correct. They pulled off a red connection, checked the sensor and cleaned and replaced the connection on the one that readout as a failure. I repeat they disconnected the sensor wire connection, cleaned it off and replaced it.

They also said that it would take 8 hours to replace the sensors and its a big expensive pain in the ass, try it again and see if the light stays off this time.

I left out of Prevost car yesterday with the light back on for the first 3 hours of my trip. I left the highway at Ext 129 for the Pilot, filled up and headed back to 95 south for Jupiter. The light was out and never came back on.

I am now guessing that the ABS system or the connection at the rear wheel is at fault. (hope so anyway)

When Rockwell designed these sensors and made its plan for their introduction in such a deep down location in the axle I do not think they envisioned the sensor would easily fail or ever fail. I do however see how the connection and the wire could fail at the axle as it is open to the elements dirt, grease, garbage of all kinds can gather at the connection to the axle, this is where I see problems with the ABS.

Conclusion, before allowing Prevost Car to replace these sensors see if a computer test of each sensor creates the all important clicking sound at each location, if it does take the connections apart and clean them before committing to a sensor replacement. i could be wrong here but it does not make much sense that the failure would always be at the internal sensor its self in all cases but rather the more exposed locations along the path back to the ABS computer.