Espar heater problems, glow pin issues

Ive had tons of issues trying to get my espar to work again. When you turn it on nothing happens. After checking resistances it seemed like the glow pin was barely out of spec, so I replaced it and the screen. Didn’t fix it. I then settled for getting the ecu reader thinking I had a locked ecu. I got error codes 20 (glow pin open circuit) and 21 (glow pin short circuit.) Naturally i found this very confusing so I replaced the ecu thinking it had to be bad with those codes. Now with the new ecu I am still getting code 21. What in the world is going on?

The new glow pin has an acceptable resistance. There’s no problem with the wires. In fact, they’re all new now up to the harness connecter with all of the replaced parts. On a hunch I checked for continuity between the glow pin and the housing thinking a short could exist there but I didn’t find any.

I’ve spent over $600 on parts and readers trying to figure this out and I am at a loss for words. All of the circuits are internal to the ecu, which is new. The glow pin reads fine from the harness. What else could it be? Is some weird short circuit condition happening on the negative side that’s blasting the glow pin? I checked the positive and negative terminals on the ecu harness and there’s no short circuit there. The fuel pump has a normal resistance.

Please help, I’m going crazy over this.

 

By nothing happens, I mean absolutely nothing occurs. No fan, no pump, no anything. The computer throws up the short circuit glow pin every time after being reset. Prior to having the tester it was a guessing game on what was wrong because it didn’t do anything to give you any hints.

The glow pin was original, at least as far as I can tell. It certainly cost enough! It looks identical, and has a resistance value that is specified.

I’m hesitant to take it to thermoking. I’d hate to count the number of times I’ve had “experts” fix my truck, just to have it break on the other side of the country and I’m the one who had to fix it in the end anyway. I figure, if I can fix it myself, I really ought to.

I mean, what are they going to do? Sell me a whole new heater? They’re going to pulling their tester in and it’s going to say bad glow plug and then they will sell me a glow plug because that’s what the manual says, and the problem will still be there and they’ll sell me a new ecu because that’s what the manual says.

I’ve done my research on this. I’m asking here because nothing I have even remotely references what to do after you’ve replaced both the plug and the ecu and the problem is still there. I’m hoping somebody either knows what’s wrong, or maybe, sees something I don’t, that gives me insight on what to check next.

 

I removed the glow pin. Unfortunately right now I don’t have any connectors which fit inside the glow pin plug. I did however do some experiments. I unplugged the glow pin and checked for codes... 20, so it realizes the plug is missing. I then plugged it in without installing it in the socket and tried to run it. Same problem, code 21. I don’t know how quickly it heats up but when I went to touch it after this test it did not feel warm at all.

I took it out and did some tests bending the wires all around while checking the resistance. It checks in around .6 ohms which is between the limits of .4 to .7. I looked around housing and didn’t see any obvious signs of a short.

I got my pin on amazon for $110. It was an Amazon choice that was well reviewed and seems to be a genuine part.

 

I see. Maybe I got a bad one then. You would think that if it was on long enough for the ecu to consider it a short circuit, it would have generated at least a notiacble heat

 

I might have something. I got to thinking, what if the glow pin isn’t bad at all? Can something else short circuit and the glow pin get blame? Looking at the wiring diagram, the ecu switches on the glow pin by moving a switch. That’s the only way for power to get to the pin. But other components share that power line. Theres no direct connection between the ecu and the pin so there’s no way to know for certain how much power it’s using other than the process of elimination, because it does know how much power the sensors use, for the sensing function itself.

The only component that gets a direct connection to power besides the pin is the fan. It’s switched on the negative side, which means any short to ground will cause a short even if the ecu has not commanded the fan to run. If it’s using the process of elimination, it might blame the pin. An internal short on the fan will also cause an excessive power draw the moment it is switched on.

The process the heater turns on is phase one, the system check. It looks at the glow pin, heat sensors, and metering pump for resistance. If they check out (1-3 seconds) it goes into preheat mode in which the glow pin is energized as well as the fan. It’s possible that a shorted fan could cause the pin to fail the self check, or fail during the process of elimination.

I previously took out the glow pin and the error changed from short circuit to open circuit. So I took out the fan and tried to start it up. Only error 31, blower motor interruption. But no glow pin error! The order of the self check is important. The glow pin is tested on the first step but the fan is not. To even get to error 31 it would have to attempt to turn on the fan, which is the second step.

Unfortunately the manual doesn’t specify what kind of resistance the fan should have, but it should not draw more than 6.5 amps, which means roughly 2 ohms, but on average it’s more like 1 ohm, which is way too low.

So, I think I need a new fan. It would explain how I can get a glow pin short and open circuit at the same time, short circuit because of the fan, and open circuit because of the fried ecu. (The new ecu no longer gives the open circuit code)

So that’s where I’m at. When I’m at the house I can test bench the fan, but the fact the unplugging the fan makes the glow pin error go away is very interesting.