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Electrical problem, voltage regulator or something else?


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Fitted an Eberspacher D4W heater and twin batteries with IBS split-charger/monitor ages ago. It worked fine, would run the heater for ages off the aux battery and there were no problems with charging/discharging. This was when I had the old 19J engine installed, with a newly fitted alternator.

Then I had the bulkhead swapped and a 200tdi fitted by a Land Rover 'specialist' a few years later.

When they gave it back to me they said they'd had trouble getting the Eberspacher to run properly citing a 'low voltage' issue as being the problem, but that they could not resolve it satisfactorily, but that although it did work, just not as well as before.

Since then although the Eberspacher has worked, it has proved problematic with the same low voltage cut-out problem occurring, and in that time the van has eaten a couple of auxiliary batteries. However I replaced the aux battery several months ago in the summer in anticipation of winter. Two weeks ago I discovered that the alternator/voltage regulator on the 200tdi was knackered and appears to have been messing about with the charging system. In addition (groan!) I discovered that my Ctek charger was also operating incorrectly so my attempts to float charge have been doing god-knows what to the battery, possibly compounding the problems, and the charger has now finally died completely. I've replaced the Ctek with a new one.

Now I have a battery that's only six months old that shows it is fully charged until the Eberspacher is switched on, then the battery monitor goes from green (fully charged) to yellow (indicating half-charged or lower) and the Eberspacher cuts out, flashing up an Error 11 (low voltage cut-out) warning. Low-voltage according to the Eberspacher manual is 10.2V.

What I've not done is put a meter at the Eberspacher heater end to see what precise voltage its reading when fired up. That's something I need to do. I have put the Ctek charger on the battery and done a 'recondition' and it worked ok after that once or twice, then refused to fire up, again Error 11/low voltage. However if I leave the Ctek charger connected to the battery I can get the Eberspacher to fire up on demand all the time without difficulty. This rules out the Eberspacher as having any major fault I reckon, narrowing it down to the battery/charging set up & current delivery.

I'm sure I'll have more questions but my initial query (on the assumption I should start with the most obvious causes first) is - given that my alternator which I replaced last week was faulty, and may indeed have been faulty since it was installed with the swapped engine, could it alone have been the cause of killing the aux battery, which is only 6 months old but seems unable to hold a decent charge according to the meter connected to it.

Given that ALL the Eberspacher and charging problems stemmed from the installation of the 200TDi with what may have been a duff alternator/voltage regulator, might I simply have killed yet another battery?

(New alternator is working a treat - all the charging tests I've done and voltage delivery is bang on according to two separate testers/meters.)

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So in short. Everything was working fine. had bulkhead changed and the heater would drop out on low voltage. After investigating battery and alternator were duff and now replaced. Charger was also duff and replaced. Heater still cuts out on low voltage. If new charger plugged in then heater works fine.

I would say that there is an earthing issue leading to enough of a drop in voltage to make the heater cut out randomly. When you connect the charger it gives it just enough juice to overcome it. Seeing as it started when the bulkhead was changed I would be looking there for the wires that go through the bulkhead and then trace then to make sure the connections are solid and the wires haven't been left to chafe on the edges of the holes where the cables go through the new bulkhead. You might find that they are damaged ever so slightly to cause a short.

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measure the voltage directly at the battery, and at the eberspacher simultaneously and fire it up. Use a proper meter that gives you actual readings, rather than the condition monitor with vague lights.

If both readings drop to 10.2v, it can only really be a duff battery, unless something inside the eberspacher is drawing an immense amount of current, but this would likely lead to smoke/flames etc :P

If the battery itself stays at a sensible voltage, but the eberspacer reads <10.2v, then theres likely a high resistance joint somewhere (in the live supply or earth to the eberspacher). You can always run some test leads directly from the battery terminals to the eberspacher to rule this out.

If both readings stay at a sensible voltage, the problem must be within the control circuitry of the heater itself.

Given it works with the charger connected, it does sound like the battery itself is to blame.

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So in short. Everything was working fine. had bulkhead changed and the heater would drop out on low voltage. After investigating battery and alternator were duff and now replaced. Charger was also duff and replaced. Heater still cuts out on low voltage. If new charger plugged in then heater works fine.

I would say that there is an earthing issue leading to enough of a drop in voltage to make the heater cut out randomly. When you connect the charger it gives it just enough juice to overcome it. Seeing as it started when the bulkhead was changed I would be looking there for the wires that go through the bulkhead and then trace then to make sure the connections are solid and the wires haven't been left to chafe on the edges of the holes where the cables go through the new bulkhead. You might find that they are damaged ever so slightly to cause a short.

That's a good call. Will have a look for chafed wires.

measure the voltage directly at the battery, and at the eberspacher simultaneously and fire it up. Use a proper meter that gives you actual readings, rather than the condition monitor with vague lights.

If both readings drop to 10.2v, it can only really be a duff battery, unless something inside the eberspacher is drawing an immense amount of current, but this would likely lead to smoke/flames etc :P

If the battery itself stays at a sensible voltage, but the eberspacer reads <10.2v, then theres likely a high resistance joint somewhere (in the live supply or earth to the eberspacher). You can always run some test leads directly from the battery terminals to the eberspacher to rule this out.

If both readings stay at a sensible voltage, the problem must be within the control circuitry of the heater itself.

Given it works with the charger connected, it does sound like the battery itself is to blame.

Ok that makes sense. I'll run some wires to bypass the existing circuits and see if it makes a difference, and measure voltages when its running. It's only in the last week since I fitted the new alternator that I've been able to get a sense of whats going on under 'correct' charging.

Thanks for the help.

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Ok got some voltage readings this am. It's about -1 deg. and frosty. Van has not been started/run since Sunday.

Aux battery at rest = 12.68v

Main battery at rest = 12.61v

Pulled apart heater multiplug (unit's main connection loom, 12 inches cable-length from heater unit) to take voltage reading - at rest reading at plug = 12.44v

Reconnect plug, start heater, it draws current for start-up cycle and cuts out immediately, low-voltage error code 11 shows.

With heater switched off again, the meter now reads:

Aux battery = 12.35v

Main battery = 12.28v

With the meter connected and taking readings in real time at the aux battery terminals during the start-up cycle, the voltage reading drops to 11.82v

I still need to bare some wires at the heater end and see what the reading is there when it's under load. (I think I might have a spare multiplug from when I replaced the circuit board and cable after it was heat damaged which would make life easier.)

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11.28v under what should be a fairly minimal load suggests the battery is knackered to me. It shouldnt be dropping that low with a few hundred watts of fan motor.

Can you stick a known electrical load over the spare battery? Perhaps a pair of headlamp bulbs or something? See if you get the same effect?

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11.28v under what should be a fairly minimal load suggests the battery is knackered to me. It shouldnt be dropping that low with a few hundred watts of fan motor.

Can you stick a known electrical load over the spare battery? Perhaps a pair of headlamp bulbs or something? See if you get the same effect?

Aye will have a go at that tomorrow. I've got the charger on it just now to get to full charge today, then I can see what the drop-off is like from full.

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Ok, battery was charged last night to 'full'. Then left overnight, off the charger. Its got warmer so not sub-zero today. At rest, engine off:

Aux battery - 12.57v

Main battery 12.34v

Reading at Eberspacher - 12.56v

Attached a mechanics 12v trailing light with a 55w bulb and switched on:

Aux battery dropped to 12.45, then 12.40 and so on until after 3 minutes it was steady on 12.15V.

Reading at Eberspacher - 12.15

That looks a tad unhealthy to me. Aux battery is 86AH deep cycle unit. I'm starting to lean towards the duff alternator/voltage regulator having knocked the carp out of the batteries in short order. Is that a fair guess?

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I'd suggest checking the earthing. Either measure the resistance of the earth cable between the heater connector and the battery -ive or, when measuring the voltage at the heater, connect the -ive from your meter to the -ive cable from the heater (rather than direct to another earthing point) so that you get a true reading all the way through the wiring for it.

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I'd suggest checking the earthing. Either measure the resistance of the earth cable between the heater connector and the battery -ive or, when measuring the voltage at the heater, connect the -ive from your meter to the -ive cable from the heater (rather than direct to another earthing point) so that you get a true reading all the way through the wiring for it.

Good idea, thanks, will try that tomorrow. (Bonus - my electrical knowledge is improving by the day!)

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