Kissling Relay Replacement

Kiltym

Active member
I found the following relay which should work as a replacement for the stock Westy Kissling relay. I have not installed it yet, but will likely order as ours is "sticking" a lot and causes a voltage drop across the relay. Quickly "exercising" normally gets it working, but only for a period of time. It would require a "jumper" cable/bar like the existing relay has.

https://www.colemanair.us/vp_asp/scripts/shopexd.asp?id=718

Another one that another Westy owner used:

https://www.waytekwire.com/item/755...YIFEhvURNAtLfoymPbAYapMR9dWIoc3BoCIiAQAvD_BwE


Now that we wired our dc-dc charger via the relay, we notice the "sticking" much more frequently (the charger often only gets about 11V when the car is running because of the relay) then if we were only using it for the Air Conditioner.
 

onemanvan

Active member
With engine running alternator field coil is energized.
This supplies current to the coil of the 'Kissling' relay.
The normally closed relay contact for the converter opens.
The normally open relay contact for the alternator closes and supplies current to the A/C.

Kissling relay simple schematic:
 

Attachments

Bernd Pfrommer

Active member
Just finished wiring my Renogy DC/DC charger and sure enough: now I realize the Kissling is broken. I never noticed before because it is stuck in "Meanwell" mode, and I never run the AC off the alternator. Time to replace it.
@Kiltym did you ever replace yours?
 

Kiltym

Active member
Installed a manual blue sea battery switch. Dealing with the relay was more work then it was worth for us as we spent 90% time unplugged from AC power. Others have done the same as the switch won't really ever fail.
 

Bernd Pfrommer

Active member
Installed a manual blue sea battery switch. Dealing with the relay was more work then it was worth for us as we spent 90% time unplugged from AC power. Others have done the same as the switch won't really ever fail.
Should have done the same. My Kissling replacement just failed on me, somewhere near St Louis, MO. Do you have pictures of where you installed your switch and how you routed the wires there? I know you sold your Westy, but maybe you still have the pics.
 

Kiltym

Active member
Should have done the same. My Kissling replacement just failed on me, somewhere near St Louis, MO. Do you have pictures of where you installed your switch and how you routed the wires there? I know you sold your Westy, but maybe you still have the pics.
I looked, and cant find any photos, sorry. I mounted the switch through the bulkhead basically where the relay was mounted. So the wire connection were in the same basic location. Then the switch was accessed on the other side in the storage area....

Sorry I don't have any photos!
 

onemanvan

Active member
I looked, and cant find any photos, sorry. I mounted the switch through the bulkhead basically where the relay was mounted. So the wire connection were in the same basic location. Then the switch was accessed on the other side in the storage area....

Sorry I don't have any photos!
FWIW: I used this switch - https://www.amazon.com/gp/product/B0053HQ88S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

The main reason I went with that switch was because the stud size is 5/16
Most of the other switches out there have 3/8 studs
The ring terminals on the wires are 5/16

FYI: I have noticed that the studs on my switch get excessively HOT when current is flowing!
That suggests to me the switch is either undersized or poorly designed...

The yellow wires are something I added for the A/C enable circuit.
OK - so you ask what the heck is an A/C enable circuit?
It's the wire that goes to the box full of relays under the water heater
whose purpose is to inform the Kerstner there is power available for running the A/C.
That line is energized by either the output of the MeanWell power supplies or the alternator field coil.
I think the main purpose of that circuit was to prevent you from running the A/C off the starter battery when the engine is OFF.

The Kerstner A/C was installed such that it could be powered by AC or DC.
IMHO trying to run the Kerstner A/C off the alternator is asking for trouble.
I have NEVER run my A/C off the alternator and probably NEVER will!
Burning out the alternator while traveling around the country is NOT something I want to risk!

A safe and simple alternative would be to simply 'hard wire' the Kerstner to ONLY operate off AC.
When I say off AC I mean either shore power or generator.
That option would entail mounting a terminal post in the area where I mounted the switch.
For example: https://www.amazon.com/gp/product/B005261UBU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
Then take the center wire and wire on the right as pictured below and bolt them onto the junction block.
The wire on the right is output from the MeanWell power supplies.
The center wire supplies current to the Kerstner A/C.
The wire on the left goes to the starter battery / alternator.
Also mount the A/C enable wire on that post.

If you absolutely had to run the Kerstner off the alternator you could temporarily bolt the alternator cable onto the post.

That's my two cents worth...



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Bernd Pfrommer

Active member
FWIW: I used this switch - https://www.amazon.com/gp/product/B0053HQ88S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

The main reason I went with that switch was because the stud size is 5/16
Most of the other switches out there have 3/8 studs
The ring terminals on the wires are 5/16
Thanks, that's good to know that the terminals get hot. I fear it's some other conductor inside the switch that's heating up. Probably will go with blue sea switch if it fits. Also thanks for the pics, very useful. Will try to mount my switch the same way, easy and reasonably accessible.
 

Bernd Pfrommer

Active member
Hmm, so after your remark on the terminals getting hot I researched more into the Blue Sea Systems 6008 that I had planned to use. It has 3/8 studs.
Here is what one reviewer on Amazon wrote: "The studs are 3/8" not the 1/2" they should be to handle 300 amps. With just 145 amps in 3 minutes the studs were hot with fresh new battery cable ends."
Here's another guy saying the Blue Sea 6006 switch terminals get hot at 200A
The "HD" high-current (rated up to 500A) switches from Blue Sea use 1/2" terminals. Before I go there I will try to load my existing blue sea 6008 (selector for AC source, another project...) with the max that the AC can draw (maybe 75A) and see if the terminals get hot.
 

onemanvan

Active member
Hmm, so after your remark on the terminals getting hot I researched more into the Blue Sea Systems 6008 that I had planned to use. It has 3/8 studs.
Here is what one reviewer on Amazon wrote: "The studs are 3/8" not the 1/2" they should be to handle 300 amps. With just 145 amps in 3 minutes the studs were hot with fresh new battery cable ends."
Here's another guy saying the Blue Sea 6006 switch terminals get hot at 200A
The "HD" high-current (rated up to 500A) switches from Blue Sea use 1/2" terminals. Before I go there I will try to load my existing blue sea 6008 (selector for AC source, another project...) with the max that the AC can draw (maybe 75A) and see if the terminals get hot.
FWIW I previously dis-assembled my switch to see what was inside. I suppose all the switches are somewhat similar in design. What I observed was that the contact area is really small and not very much force being exerted on the contacts. So it's not surprising that there's a lot of resistance to current flow - which equates to heat. Simply bolting the two ring terminals together would eliminate that problem - but it's only practical if you primarily run the A/C off generator or shore power...
 

onemanvan

Active member
I don't use my Kerstner A/C very often. During my summer travels when I'm trying to 'escape' the heat of southern Arizona I usually dry camp 'out west' in public campgrounds that are higher than 8,000 feet. Even then - because the Westy is so poorly insulated - the interior can get uncomfortably warm. My solution to that is https://photos.app.goo.gl/MjeSES6CMfDaijuh6. What goes up must eventually come down, for groceries and laundry. Those chores take some hours and typically occur at lower elevations where it's HOT so that's when I typically run the generator/Kerstner. Sometimes I also run it while driving when it's really HOT because my engine losses boost if I"ve got the dash A/C on. Read this thread if you're curious about that: https://sprinter-source.com/forums/index.php?threads/111973/ I've measured the temperature of the two terminal studs on my switch after the A/C has been running for some hours. They get very HOT, around 160 degrees! I measure about 80 amps through those terminals. FWIW when running A/C off shore power I measure 1,400 watts power consumption!

Hopefully this background information helps explain why I've revised the wiring associated with the battery switch I installed to replace the Kissling relay. The main objective was to eliminate the hot terminals on the switch while preserving all of the functionality. I'm not suggesting this approach is best for everyone. However, if you have a DC to DC charger for your house batteries and you typically run your Kerstner roof A/C off shore power or generator then you might find this works well for you. Also - possibly unique to my setup - I've replaced the OEM gel batteries with lithium batteries which do not tolerate excessive heat. So I remove my two lithium batteries when the van is in storage. That's why I included the option to power the DC circuits off the starter battery. My roof mounted solar panels keep the starter battery charged. For additional information related to my wiring mods' refer to this photo album: https://photos.app.goo.gl/bG5UakzFcLXrvXa58

The key point here is that I've bolted the output of the Meanwell power supply and the input to the Kerstner roof A/C to the 'common' stud on the four way battery switch. Now that those two ring terminals are in direct contact there is no voltage drop, therefore no heat is generated. That junction now remains at ambient air temperature!

As I've mentioned before I do NOT recommend running the Kerstner roof A/C off the alternator. IMHO the output stud on the alternator gets excessively HOT! If I need to run the Kerstner while driving - for example pulling a long mountain grade on a hot day - I think it's better to run the roof A/C off the generator. With the revised wiring it's still possible to run the A/C off the alternator. However since there is no longer any interlock to prevent the A/C from running when the engine is OFF there is a risk of killing the starter battery. When I say interlock I'm referring to the "A/C enable" and "Alternator field coil" wires. With the OEM Kissling relay the "A/C enable" line was activated automatically to prevent killing the starter battery.

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