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Old 11-06-2018, 10:24 PM   #1
Robert Foster
 
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Default Espar Heater/#4 Fuse Has No Power

On a recent five night trip my Espar heater worked flawlessly for the first four nights and on the fifth night when I went to turn it on.....nothing.

A check across the #4 fuse in the fuse block behind the bench seat shows that there is no current across the #4 fuse terminals. There is current across all other five pairs of terminals in the fuse block. A check of the cables entering the rear of the fuse block shows all is well.

Nothing was worked on in the van between nights four and five.

My original ECU in the Espar was replaced with the North American ECU variant so my central controller no longer is the thermostat for my Espar. There was a simple Espar Rheostat installed presumably when the ECU was replaced. This is going to be a good time to install the DigiMax 1000 that I have had while I diagnosis and correct this power outage.

Any ideas of where I should investigate next for why there is no current going through my #4 fuse, which is presumably the reason why my Espar isn't working. I am assuming that the problem is upstream from the Espar and not at the Espar itself, but I could be totally incorrect on that. I pulled my Espar out last year and serviced it successfully myself and I do not remember any kind of reset/fuse or circuit breaker on the Espar itself.
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Old 11-06-2018, 11:13 PM   #2
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Default Re: Espar Heater/#4 Fuse Has No Power

I'm confused with respect to your terminology...

Current is a measurement of amperage flowing through a circuit - think of it like volume ( IE: GPM - gallons per minute) of water flowing through a pipe.

Voltage is basically a measurement of potential difference - think of it like water pressure (IE: PSI - pounds per square inch).

A more meaningful way to relate what you're seeing might be to say:

"I measured the voltage on both sides of fuse #4 and"

1) saw 12.8 volts on both sides."
2) only saw 12.8 volts on one side".
3) saw zero volts on both sides".

1) If you're seeing 12.8 volts on both sides then it's possibly a controller issue. In which case it might be an opportune time to install your Digi-Max:-)

2) If you're only seeing 12.8 volts on one side of the fuse then the fuse is probably defective.

3) If you're seeing zero volts on both sides then pull the fuse block out ( held in by two screws ) and check the wiring on the rear of the fuse block. If memory serves all the power to the fuse block is supplied by two 8 awg wires connected to the 'big red switch' ie: the battery disconnect switch.

Last edited by onemanvan; 11-06-2018 at 11:31 PM.
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Old 11-07-2018, 01:34 AM   #3
Robert Foster
 
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Default Re: Espar Heater/#4 Fuse Has No Power

Sorry about that, let me try again.

I removed the 25 amp fuse installed in position #4 of the fuse block and confirmed that there was continuity across the two blades of the fuse. So I set the 25 amp fuse aside.

When using my multimeter to test the two terminals in fuse position #4 of the fuse block I discovered the following. (By terminals I mean, the female sockets inside of the fuse block that the blades of the fuse insert into)

1) The left terminal of #4 position has 12.4 volts present just like the other five left side terminals. This test was done with the red probe of my multimeter on the left terminal and the black probe on the grounding lug in the adjacent cavity where the battery charger is housed.

2) When I place the red probe on the left terminal and the black probe on the right terminal I get almost no voltage (0.34v) at fuse position #4 while doing the same test across the other positions in the fuse block the multimeter reads 12.4 volts. (this is what I was trying to convey in my initial post when I wrote "there is no current across the #4 fuse terminals")

I hope that is more accurate/makes more sense. Thank you for your help.
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Old 11-07-2018, 03:10 AM   #4
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Default Re: Espar Heater/#4 Fuse Has No Power

I suspect the reason your method of measurement is yielding a different result with respect to the other fuse sockets is because there is no load on fuse #4 IE: no path to ground. This would happen if the relay inside the ECU is not engaged IE: no call for heat.

The rheostat controller should have a yellow wire attached to it. When the controller is adjusted to turn the heat on the yellow wire should have 12vdc on it. That 12vdc is what engages the relay inside the ECU. If the relay is not engaged then power is not supplied to the heater. IE: there is no load on fuse #4 - no path to ground.

If you don't see 12vdc on the yellow wire when the heater is turned on then something could be wrong with the controller or the wiring associated with the controller. You can 'hot wire' the relay - IE: energize it - and force the heater to come on by applying 12vdc to the yellow wire. This is a simple test to confirm the heater is functional - IE: this forces a 'call for heat' regardless of the temperature controller settings.

Last edited by onemanvan; 11-07-2018 at 04:09 PM.
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Old 11-07-2018, 03:39 AM   #5
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Default Re: Espar Heater/#4 Fuse Has No Power

You’re results are expected. With no fuse installed, one side will be 0V and the other 12.

This test is not really telling you anything.

With the fuse installed, the side showng 0V, does it now show 12V?
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Old 11-07-2018, 11:05 PM   #6
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Default Re: Espar Heater/#4 Fuse Has No Power

Thank you for the replies. I will try out both of your suggestions as soon as I have some time and report back. Thanks again.
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Old 11-10-2018, 08:20 PM   #7
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Default Re: Espar Heater/#4 Fuse Has No Power

Kiltym, Yes, with the fuse installed (partially installed so that I can touch my multi-meter probe to the blade of the fuse) there is 12v on the right side of the fuse that measures 0v at the fuse box with the fuse removed. I am not sure what more this test tells me than a continuity test across the blades of the fuse does ?

onemanvan, Yes, when putting 12v to the yellow wire in the cable routing to the Espar the Espar heater starts up and runs as it normally does. I assume this positive test tells me that the ECU is not "locked out" and does not need to be reset ... is that correct ?

Given those two positive tests, I went ahead and installed the Digi-Max 1000, understanding that the Digi-Max can read fault codes. Unfortunately, there is no functionality with the Digi-Max either, not even any power to the Digi-Max display or LED indicator lights.

There was one question that I had about wiring the Digi-Max. The Digi-Max has six wires and the cable harness from the Espar has seven wires. The unaccounted for wire in the Espar harness that is not listed in the Digi-Max installation instructions is a solid brown wire. I pigtailed the solid brown wire into the same terminal with the Brown/White Ground Reference wire as this was what was done with the wiring on the rheostat that I am replacing. Is that the correct installation ?

Thank you.
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Last edited by Robert Foster; 11-10-2018 at 09:47 PM.
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Old 11-10-2018, 09:05 PM   #8
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Default Re: Espar Heater/#4 Fuse Has No Power

"Kiltym, Yes, with the fuse installed (partially installed so that I can touch my multi-meter probe to the blade of the fuse) there is 12v on the right side of the fuse that measures 0v at the fuse box with the fuse removed. I am not sure what more this test tells me than a continuity test across the blades of the fuse does ?"

Without the fuse installed, you will not get any voltage on the right side of the fuse box. With the fuse installed, you should, as you do. If it still read 0, it would mean the fuse is blown and needs to be replaced. But this is not the situation. And you are correct, it tells you the same as a continuity test on the fuse itself.

Cant comment on the DigiMax, sorry.....
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Old 11-10-2018, 10:07 PM   #9
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Default Re: Espar Heater/#4 Fuse Has No Power

Let's confuse things with a drawing:

Circuits.png

If you pull out the fuse, and the switch is open, you'll get what (i read as) Robert's first measurement (black probe to frame):
+12v on the left, and a 0v reading on the right (but it's really "floating", similar to the red probe waving in mid-air) .

If you measure red-probe-to-left and black-probe-to-right, you'll again see "floating" (0v on the meter).

If you close the switch (and the "thing" has a current path between its red and black wire), then the "right" will become a "real" ground ... the red probe will see +12v and the black probe (on the right) will be a "solid 0v ground" and the meter will read +12v.

If the "thing" had some internal switch/relay (or fault) that did NOT provide a path between its red and black wires, then the "right" fuse socket would appear the same as the first "switch open" case: it would still be "floating" and the meter would read zero.

Putting the fuse back in (if it's a good fuse) would make both the Right and Left sides of its socket have the same potential, which would be +12v if measured to the ground lug.

--dick
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Old 11-10-2018, 10:30 PM   #10
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Default Re: Espar Heater/#4 Fuse Has No Power

Regarding the brown & brown/white wires: Yes - they should both lead to the same place IE: ground.

Regarding yellow wire test: If the heater runs when 12vdc is applied to the yellow wire then the heater ECU is NOT locked out.

Regarding the Digi-Max: Since your rheostat installation is not OEM I have no way of knowing how it was wired in. I don't even know where it's physically located...

However - the following notes might help in further trouble shooting:

There are three inputs to the controller:
Red - battery positive ( probably the coach battery )
Brown - battery negative ( probably the coach battery or chassis ground )
Blue/White - diagnostic line from the ECU

There are three outputs going from the controller to the ECU:
Yellow - heater enable / call for heat
Grey/Red - temperature setpoint
Grey - temperature sensor

You should be seeing 12vdc on the red wire. If not then you need to trace that wire back to it's source to determine why. The installer may have put an inline fuse at the source. But again - I have no way of knowing where the installer tapped into the 12vdc supply.

The brown wire[s] should be tied to ground - so perform a continuity test between the brown wire[s] and chassis ground - should be close to zero ohms. If not then you need to trace that wire back to it's ground point and insure a solid connection to ground.
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Last edited by onemanvan; 11-11-2018 at 03:22 PM.
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