Eberspacher power source.

[robin.richard]

Hello,

I have a question for the electrical minded mechanic or a BN4 Eberspacher user.

I have been running my Eberspacher for two winters now. Great accessory for those cold morning drives. Especially for passengers in the back. I used the 67 and earlier instal instructions, except I didn’t run the power off the starter terminal 30, rather I run it directly off the battery + post. Everything seems to run fine. It Produces heat as it should. Unfortunately if I run the heater without the motor running it instantly kills the battery and I can’t start the bus.

So my routine is - start the bus, then turn on the heater, have a nice and warm drive, once I get to my destination I turn the heater off and it goes into its cool down cycle, then when the heater shuts off I turn off the engine. If I accidentally turn off the engine before the heater goes off I can’t start the engine. I know the glow plug in the heater draws a lot of volts but once that shuts off I didn’t think the heater drew much while running and during the shutdown cycle.

Is this issue because I’m running the heater straight from the battery + post? Would this correct itself if I run it from the starter or the regulator? Easy enough to do, but wanted to ask first.

I also have a lithium leisure battery under the foldout bed and I am considering running the heater from it but I would need to change some wiring from the switch.

What do you think is causing the issue?

-Rich
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[busdaddy]

Battery or starter terminal doesn't matter, does that heater have a glow plug?, or just a spark plug?, if glow the flame switch could be defective and not shutting it off, that's a huge draw.

What size is your battery?, how old?, alternator or generator?
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[robin.richard]

Busdaddy,

The Eberspacher is from ‘68. It has the glow plug and spark plug. I don’t know the size off hand but the battery is about three years old. Running stock SP with generator.

The strange thing is the battery still runs the heater/lights/stereo but doesn’t have enough cranking amps to turn over the engine. Even with running the heater without engine running only for the length of time it takes the cooling cycle to turn off the heater. What is that, 2 mins?

Once the battery is jumped and I drive home (45mins) the battery is fine and starts with no problems.

I put a trickle charger / tester on last night. Tests show battery is good.

Tomorrow I will check to see if the glow plug is going out once the heater warms up. I work as it should during bench tests before I install the heater two years ago. But I wouldn’t think a glow plug would run down the batter in two mins.

-Rich
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[BarryL]

[busdaddy]

[robin.richard]

[Nitramrebrab72]

Those heaters drain a quite a bit of energy especially at the end of your journey when the cab is up to temperature the thermostat will be flickering between on and off regularly doing many more start ups for the same time period. Not the case when the cab is getting upto temp , that coupled with the effects of the battery temperature vs cranking amps. The two combined will show up any defects in either the charging circuit or the battery and starting circuit. Or a combination of the two. Have the battery tested (with a battery reader to check for available capacity and maximum available CCA). Check with the chart below for temp vs CCA your battery for the climate you have and the attached aux. might not be big enough. Test the voltage at the battery with the engine running, it should be between 13.8 and 14.4 the latter would indicate a strong alternator.

[crofty]

The heaters do draw a significant amount but this sounds like a battery Starter issue.
Ive run my heaters for long periods and never had a problem starting the bus.
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[Clara]

[Ollie W]

I concur with the last two responses, you should be able to run the heater for a while on a fully charged battery and still be able to start the bus.

Changing the power wire draw location likely wont change anything. If you can, I'd put an amp meter to it, let it go through a cycle and see what the draw is like and if there's a spike or continuous draw even after it's all cooled down and off.

Of course, it's getting cold, so in all reality, I'd stick with the routine that you know works for now and then address it in the Spring.

[robin.richard]

[busdaddy]

Those are some really low numbers for engine running, ever considered raising the idle speed?
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[Ollie W]

Agreed about the low voltage. Do you have an adjustable voltage regulator by chance? If so, bump it up a bit. If not, clean the connections and bump up the idle.

[robin.richard]

Busdaddy and Ollie,

I see your point. I checked the volts before departing work this afternoon.

Before starting - 12.8

Engine running after warmup - ~ 13.89

I didn’t check with the heater running.

I’m going to follow your advice and clean all connections and bump up the idle a little. I don’t believe my BOSCH regulator is adjustable.

What should the volts be a normal idle, 14.0+? How about when not running, 12.5+?

-Rich
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[busdaddy]

12ish stopped and close to 14 running is the normal, the regulator cuts out below a certain output voltage to prevent reverse current flow, that ~12.5 sounds like no charging is happening at that speed.

You don't happen to have a degree pulley do you?, how low in the generator pulley does the belt sit?
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[robin.richard]

Busdaddy,

I have a standard OG pulley. Admittedly the belt might be a little loose.

All these great suggestions are just reinforcing what I already knew to be true, that I need to do my annual engine tune-up sooner rather than later.

I will check volts while the heater is running tomorrow.

Again, thanks for all the great insight and suggestions.

-Rich
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[robin.richard]

Busdaddy et al,

All is sorted out now…I believe.

All these great suggestions got me thinking about a loose belt, dwell angle, timing, etc. Once I tighten a loose belt, reset the dwell angle to 47, set timing at full advance with timing light and raised the idle speed to approximately 1000 rpm, I got good numbers. I even tested running the heater for 20mins. with the engine off. Then started the bus with no issues. I’m going to try the same test tomorrow morning when the temps are much lower.

One thing I noticed is while the heater was running without the engine running, the battery measured @ 12.5 -12.6 volts. Once the heater ran through its cool off period and shut down the battery reading went up to 12.7 volts, where it stays when the engine is not running. With the engine running at idle the battery measured 13.7 -13.8 volts, with the engine running at idle and the heater running it falls to approximately 13.5 - 13.6 volts.

I still have more to do including cleaning all electrical connections, but I believe I’m now in an acceptable range.

Please let me know if I’m still off.

-Rich
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[busdaddy]

I'd be satisfied with that, good job!
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[Eric&Barb]

[robin.richard]

Eric&Barb,

My bus is a late 67 model so I’ll need to check for the soldered connections.

I do need new battery cables, both pos and neg. I’ll check out WW.

I will also use your advice on the dielectric grease. I use it for most things electrical. And having grown up in the PNW I am very familiar with the endless wet/cold weather. It may come as a surprise, but I really miss it.

-Rich
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