SHC 60 Heater no start.

[M Collin]

I recently acquired an SHC-60 heater on FB Marketplace minus batteries and ducting. 69hrs on the clock. Also included the harness to run unit on external batteries.
I charged a couple of lawn tractor batteries and they read 13.5 volts each.
After turning the power switch on, all lights illuminate briefly, combustion and convection blowers run for 5-8 sec, then stop. Couple seconds later, the fault light flashes continually and won't stop. The only things missing are the battery heater and temp sensor. I'm going to try a 4.7-5k resistor across the temp sensor leads, but don't think that will make a difference. No fault code for that showing up.
Any ideas or info would be greatly appreciated. I do have a downloaded copy of the service manual, and didn't see any info related to this issue.
Thank you

 

[M Collin]

Well, I was right. The resistor to cheat the temp sensor on the Batt pack didn't make a difference. I guess it's on to checking the relays.

 

[flyfishtrailer]

Did you count the number of beeps with the error light and cross check what the machine is telling you? The error codes are on the back of the control box if I remember correctly, but definitely in the TM. What temp was it that you were trying to start it in?

 

[M Collin]

Did you count the number of beeps with the error light and cross check what the machine is telling you? The error codes are on the back of the control box if I remember correctly, but definitely in the TM. What temp was it that you were trying to start it in?

Yup. I sure did. Several times. When the beeping/flashing continued after the count of 18 several times, I figured something was not right. I tried this with a low setpoint as well as high.

 

[flyfishtrailer]

So I am trying to remember who here had a thread that talked about fooling the battery sensor. I have never had mine do that (not using the battery pack issued, but two battery's). I have used it in temps around 25-30 and not had it refuse to start. Let me do some more digging.

 

[KN6KXR]

When you say a "harness to run unit on external batteries" do you mean the connector that's meant to jump a battery pack? I can't recall seeing anything other than that on the units I have.

You have to use two separate batteries connected to the proper leads (batt1 and batt2). The system connects them in series when it powers the glow plug. If you connect the batteries to both DC pos/neg, or use one source, it will likely pop a chip on the PCB. I found this out the hard way. I suggest you carefully inspect the PCB for damage. If this has occurred it will be obvious.

 

[ZiggyO]

When you say a "harness to run unit on external batteries" do you mean the connector that's meant to jump a battery pack? I can't recall seeing anything other than that on the units I have.

I make that adapter harness, and yes, it requires two separate batteries to function properly.

Z

 

[M Collin]

When you say a "harness to run unit on external batteries" do you mean the connector that's meant to jump a battery pack? I can't recall seeing anything other than that on the units I have.

You have to use two separate batteries connected to the proper leads (batt1 and batt2). The system connects them in series when it powers the glow plug. If you connect the batteries to both DC pos/neg, or use one source, it will likely pop a chip on the PCB. I found this out the hard way. I suggest you carefully inspect the PCB for damage. If this has occurred it will be obvious.

The harness was purchased by the previous owner from a guy that sells them on ebay. This eliminates the need for the OEM $950 battery. The sheet that came with the harness said to use the white wires for positive and black for negative. My experience with RVs and camp trailers DC systems was Black for Hot and White for Negative. Before connecting the heater to the batteries, I double and triple checked to make sure everything was right.
No trouble codes. Just the constant beep/flash after initializing.

 

[ZiggyO]

The harness was purchased by the previous owner from a guy that sells them on ebay. This eliminates the need for the OEM $950 battery. The sheet that came with the harness said to use the white wires for positive and black for negative. My experience with RVs and camp trailers DC systems was Black for Hot and White for Negative. Before connecting the heater to the batteries, I double and triple checked to make sure everything was right.
No trouble codes. Just the constant beep/flash after initializing.

As I said, I make them and sell them both here and on ebay. And yes, the white wires are positive and the black are negative. It needs two batteries to work properly. If you hook both sets of leads to one battery, it will cause a short when the heater tries to switch the batterypacks for starting (series/parallel operation). I think in your case this may have happened (or a reverse polarity hookup), resulting in arced contacts on your relay board at best or a blown ic on the control board.

Z

 

[M Collin]

As I said, I make them and sell them both here and on ebay. And yes, the white wires are positive and the black are negative. It needs two batteries to work properly. If you hook both sets of leads to one battery, it will cause a short when the heater tries to switch the batterypacks for starting (series/parallel operation). I think in your case this may have happened (or a reverse polarity hookup), resulting in arced contacts on your relay board at best or a blown ic on the control board.

Z

As I said, I make them and sell them both here and on ebay. And yes, the white wires are positive and the black are negative. It needs two batteries to work properly. If you hook both sets of leads to one battery, it will cause a short when the heater tries to switch the batterypacks for starting (series/parallel operation). I think in your case this may have happened (or a reverse polarity hookup), resulting in arced contacts on your relay board at best or a blown ic on the control board.

Z

I looked back in the thread and didn't see anything mentioning you as the source for these harnesses (quality product BTW).
I know that you need two separate batteries of the same amp/hr capacity.
Hopefully it will be obvious when I pull the control board. Have you had any success in repairing these boards? I think there are 7 or 8 relays on it. Next rainy day, I'll pull the board and report back with my findings.

 

[ZiggyO]

If you are lucky enough to have just a cooked relay, they are fairly easy to swap out (use a good pencil type soldering iron). If an ic is cooked, it will be far easier to just source another heater. The only good thing about all the heaters that came out without control heads is the availability of spare parts. I caution anyone who has these heaters to consider grabbing an extra unit or two for spares while they are coming out on droves. Otherwise it will be like the jeeps/cucvs/m35s/etc--- here one day, gone the next; and now out of this world prices.

Z