[Jerry]

I think there are two lights associated with the chassis electrical system in that vintage coach. A red light indicates an issue with voltage, high or low.

A blue light indicates an issue with the relationship between the chassis 12 and 24 volt systems.

Both are driven by the Vanner monitor located above the chassis batteries.

The red light will come on to indicate the chassis system voltage is out of an allowable range due either to a failed alternator not charging the batteries or excessively high voltage. I cannot remember the exact upper and lower limits, but for this discussion assume the Vanner will alert when the voltage drops below 24 volts or exceeds 30 volts. Any time the light is on the immediate response is to verify the voltage has come out of the allowable range, or if it is correct. For convenience the easiest place to check using a voltmeter is at the chassis booster cable attach points. With the engine off the voltage can be expected to read about 25.2 to 25.6. With the engine running on high idle the expected voltage would be around 27.7 volts. If the voltages are at or near those voltages the Vanner monitor might be defective.

If the blue battery balance light comes on the 12 volt system is not exactly 1/2 of the voltage reading of the 24 volt system within 1/2 volt. Again if the light comes on the actual voltages should be checked using a volt meter. For convenience they can be checked at the base of the Vanner monitor, but I prefer the terminals at the Vanner equalizer. The 12 volt reading should be within 1/2 volt of being 50% of the 24 volt value. If those readings are within the range the monitor might be defective, and if they are outside the allowable range the equalizer could be defective.

It is important if you get a warning on the dash you pay immediate attention to it.

[Archived]

26.5 is low but I doubt that is your issue. Your coach probably has an adjustable voltage regulator which may need to be tweeked to a voltage rate appropriate to the type of batteries your coach is using.

If I am correct in my suspicion of your coaches malady, you will find that you will not have any daytime running lights and will probably be having issues with the road air system. Most likely cause is a small wire on the back of the alternator has broken off the alternator.

[Per]

I just had the same thing happen to me, My red battery came on….On my coach I found info in the manual sending me to relay # 33 which I ordered from prevost for appx $10 and when it arrived I plugged in the new one and all is well…hope this helps

[Archived]

Ive had that battery light come on even though the other guages showed the correct voltage. Like Jon said, go back there and make sure all the connections are tight between the alternator and voltage regulator, no wires have rubbed through, along with taking reading with a multimeter.

I tried to tweak the regulator with no luck so replaced it and everything was all good again. It had been sending a bad signal to the dash causing the light to come on.

Prevost part #562775 for the 24V($206.75) & #562776 for the 12V ($209.72).

[Jim/Chris]

Ignore the dash gauges. The most accurate readings are going to come from the source or as close to the source as possible and before you do any trouble shooting or checking you need to know the voltages, engine running and engine off.

[Ron]

Thank you – each of you. I will go back over and check those items. I do know the Prevost gauges indicate nearly 27 v on the 24 v side and about 14 v on the 12 v side. I assume they are correct but I will confirm.

Wave

[Bill]

For diagnosing an issue the gauges are a quick but not very accurate means of getting needed information. I have a single alternator charging both house and chassis batteries simultaneously. I have voltage gauges for the house and chassis side by side and they show at least a 1/2 volt reading in voltages. When you are dealing with situations where 1/2 volt makes a big difference you need to know the values you are getting are accurate.

If you have an alternator voltage regulator putting out just 1/2 volt more than the Prevost setting you could be cooking the chassis batteries as an example. Your proper relationship between the 12 and 24 volt systems on the chassis is important and a 1/2 volt error in the reading can mislead you into thinking you have or do not have a problem.

When you get a warning light on the dash use your multi-tester to get accurate readings so you know if you do have a problem or if the monitor is failing.

[Dana]

251 at jump point engine off

26.65 Engine on

[Archived]

My old coach had the battery light come on years ago and found a bad battery in the 31 series set. Replaced the set and no more light. Your newer coach might be different.

[Archived]

Wave,

The voltages seem low. Can you provide the voltages from the base of the equalizer, 12 and 24 volt engine on and engine off?

Can I assume no appreciable loads such as AC on and at high idle? If not retake them with the AC off and at high idle.

[Archived]

ok here is the information:

24.87 v at the Vanner with engine off

12.40 v as above

26.74 v at Vanner with engine on -all accessories off

13.30 v as above

Wave

[Archived]

Voltages are lower than I would expect to see. Before I would start messing with the voltage regulator I would check the batteries. How old are they?

If they check out, then I would adjust the voltage at the regulator up to 27.7.

Do the batteries lose power over a short period of time?

The good news is it appears the equalizer is doing its job.

[Archived]

Thanks again for working this issue with me. The start batteries are all within 18 mos old and the house are less than 12 mos. No issues with starting. I do not leave the 24 v chgr on all the time.

No idea of where to raise V on Vanner.

[Ron]

Age is no assurance the batteries do not have a defect so while it is a pain removing all the cables so they can be individually tested you do want to make sure each is in good condition and tests OK.

I’m familiar with the old style Delco voltage regulator and Prevost had a detailed section in the shop manual covering the device, including how to set it. If they have switched to a different voltage regulator it is likely it is also covered in detail in the shop manual availtable on the Prevost Car site in the publications found through parts and service.

[Archived]

OK , YOU WANT ME TO READ THE MANUAL😊. (Insert happy face here)But there is not one for the Vanner. I did find some info on line. My Prevost manuals may be incomplete or I did not see the needed info.

I will test the start batteries (24v) but should they not be tested under load with something like the one pictured?

I assume I would need to check the house side as well (12v) since the Vanner looks at both to equalize.

I believe the voltage adjustment if needed is made through the Trace inverters parameters is that correct?

I will probably slip over to Marathon in Coburg since I am in Newport, Or. right now and let them have a look but I am learning from each caution light . I hold my breath and hope each time I start the engine.

Wave