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.

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.

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.

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.

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?

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.

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.

"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.....

Let's confuse things with a drawing:



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

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 should be tied to ground - so perform a continuity test between the brown wire 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.

Thank you very much for the replies.

All I had time to do today was check the voltage on the red and brown wires leading to my Digi-Max.

The brown negative did indeed have 0v on it when grounded to the brown common lug at the AC charger located in the wall below the kitchen drain board/storage area.

The red positive wire also had 0v instead of the much needed 12v.

So there's no voltage at the outgoing side of the fuse block terminal #4 and no voltage at the positive red wire leading to the Digi-Max. What is the assumed/typical relationship between these two wires ?

I was under the assumption that the relatively large capacity positive wire leaving fuse block #4 went directly to the Espar supplying all power needs of the Espar's fan, ignitor and ECU, with the red positive wire serving the Dig-Max coming from the Espar. Is this an incorrect assumption ?

When I removed my Espar to service it last year I do not remember seeing any type of inline fuse.

Both the rheostat controller and Digi-Max get their power from an external source - IE: NOT from the Espar heater. Typically an installer would get power from the house battery. So trace the red wire connected to the controller back to it's source and determine where the fault is occurring - possibly an inline fuse. If that's not possible then add your own wire - IE: find a convenient nearby source for 12vdc - install an inline fuse near that source - run a new red wire from the fuse to the controller - 5 amp fuse should be adequate...

As you can see in the attached wiring diagram ( D2 & D4 have similar wiring ):

1) The controller gets it's power from the house battery via fuse 2.7.1 ( 5 amp )

2) The heater gets it's power from the house battery via fuse 2.7 ( 20 amp )

Update.

The Espar is working as it should, actually better than it ever has, since this process motivated me to replace the rheostat with the Digi-Max.

My original problem of the Espar not coming on was indeed, as onemanvan pointed out, just a blown fuse in the positive line supplying the controller (formally the rheostat now the Digi-Max). That fuse, which I had totally forgotten about, is located in a weather resistant fuse holder that hangs out of the metal enclosure housing the Espar under the chassis.

I have run the Espar for multiple times for many hours since installing the Digi-Max and heat is now delivered more comfortably and consistently than it ever has been before in the four years since I purchased the van. I think the fact that the rheostat was located on the D pillar by the sliding door and subject to temperature swings and drafts while I installed the Digi-Max on the end of the upper kitchen cabinet partly accounts for the better heat delivery.

Thank you again for all the replies.
Robert

As I've said before, I might start putting systems on separate controllers where possible. Increasingly, I see the central computer in the overhead console as a single point vulnerability, and the fact that you can't get another one means you are dead in the water without it.

Nice work, Robert.

You can get a replacement central computer. I posted a link here in another thread somewhere... Just FYI.

Riptide said:

As I've said before, I might start putting systems on separate controllers where possible. Increasingly, I see the central computer in the overhead console as a single point vulnerability, and the fact that you can't get another one means you are dead in the water without it.

Nice work, Robert.

Click to expand...

I completely agree. The buttons for adjusting the refrigerator on my overhead console are less than perfectly responsive, which has me knowing they will fail me someday, but hopefully not before I remodel my interior.

Here's a picture of my Digi-Max installation. Easy to reach from the bed and keeping it off of an exterior wall were my goals, so the end of the upper cabinet was a perfect location and an easy place to route the cable to.

Kiltym said:

You can get a replacement central computer. I posted a link here in another thread somewhere... Just FYI.

Click to expand...

Good posting all. Here is the link for the central electronics:
https://www.vwbusshop.de/epages/Gue...hops/GuenzlClassicParts/Products/900001506048

I repaired mine twice by opening and cleaning/re-coating the contacts, some of which became almost impossible to use in cold weather. I would suggest cleaning first with alcohol. If no results, coat button pads with carbon contact paint. My first job only lasted a year so the second time I also re-coated the contacts on the circuit board but that was next to a nightmare. It required so much patience because it's so easy to short the interwoven contact fingers with the paint. It required magnifiers and toothpick application; lots of starting over with paint remover. I'd like to know a microelectronic company to do it the next time; but hopefully that won't be needed.


AL

CaptnAlinTiverton, are you able to give a readers digest version of how to remove and access the central computer and the contacts within, while avoiding any potential pitfalls ....?

Here's how OneManVan did it:

https://sprinter-source.com/forum/showthread.php?t=46912&highlight=Remove

Other descriptions/instructions would be valuable too as different perspectives help.

OldWest said:

Here's how OneManVan did it:

https://sprinter-source.com/forum/showthread.php?t=46912&highlight=Remove

Other descriptions/instructions would be valuable too as different perspectives help.

Click to expand...

He's got it right! The dome light comes out by just grabbing the clear plastic edges with fingers and thumb and moving forward or backward while prying down. You'll see the lips on the plastic when it releases. The tabs for the unit are more obscure but you can actually feel them on the sides of the unit when you stick your finger in the light hole and put pressure on each end while pushing forward (towards rear of vehicle). After unplugging connector, you want a clean work bench/table where you can sit for a while; with the unit face down, carefully pry the black frame away from the white box and lift the box away.

I used the carbon contact paint made by Caig but I found it to be flaky when dry. Just Google carbon contact repair; there's plenty there to study, especially what others have done. I did mention just cleaning with alcohol for first try but VERY LIGHTLY with Q-tip while being careful not to leave cotton hair. DON'T GET TOO WET OR RUB HARD; purpose of cleaning is NOT to remove contact material. (I didn't try stick-on pads fearing most stick-on's fall off and leave residue). The Chemtronics coating might be the best but it is twice the price. I always hate to pay a lot for chemicals due to their short shelf life.


AL