Smokin’ wires tracing no heat problem in 1962 Chevy C10 adds up
Driving an old pickup through the winter like my ’62 Chevy C10 “Swede” is a game between keeping the wheels from spinning and not freezing in the cabin. While 140 pounds of sand bags and snow tires most solve the spinning tire issue, a warm cabin is more complex with a heat problem.
A few years ago, I tore out the entire heating system from the heater box, the heater ductwork into the cabin and the switch box on the dash.
I cleaned up all the pieces, bought a new heater coil, new blower motor, new resistor switch and new levers as well as new radiator hoses.
The result was a working heater. Hooray! Except, well, it barely keeps the cabin above freezing to death.
How could this be? Everything is new!
Well, apparently it is more complicated than that.
It turns out the heater motor does indeed blow warm air. However, this air is fighting a battle against the cold air invading the cabin from multiple places.
For example, the new door weatherstripping does a good job keeping the air out, but the metal doors and side windows do nothing to keep the hot air in. You can literally put your hand near the window and feel the cold air coming in. And yes, this is rolled up with an anti-rattle kit making the windows fit snuggly.
The other issue and more obvious problem is the firewall. Over the 50+ years the truck has been around, there have been several holes put in the firewall, and the firewall itself is really just a thick piece of, what amounts to be, cardboard. It basically resembles a piece of Swiss cheese.
Now the larger problem is the heater motor, which decided to stop working. Weird, but not an uncommon problem for something to work and then not. Tracing the issue, I found an unplugged wire running to the fuse block as the result of my ill-fated summer plan to clean up the rat’s nest of wiring behind the dash.
Yeah, don’t do that, ever.
Finding the right wire and plugging it in is simple. Turn the engine over and then turn on the fan switch. Nothing. Hmm… Then, a few seconds later, smoke fills the cabin.
Kill the engine and grab the wire to unplug it from the fuse box. Whew! Checking the wire, the smoke slows and starts to clear out of the cabin. The only reminder of this episode is the new wire burn mark on my thumb thanks to grabbing the overheated wire.
Smoking wires are nothing new in automotive, and in working on Swede, it’s never a fun experience. What it means is somewhere along the line, the wire is getting overloaded.
Grabbing my Power Probe (yes, it is literally called that), I trace the continuity of the circuit. Basically, this means, I start tracing the presence of a good ground and power at different points of the electrical circuit for the heater system.
With the Power Probe, all I have to do is touch the ground and it will light up green if it is good. I then can put it on a wire, and it will tell me how many volts I have at this point.
Pretty damn handy piece of equipment, really.
Running the test, I have a good ground everywhere (ground issues are often THE culprit on old trucks).
Next, I have power to every spot, so that’s a relief.
I try another wire and after filling up the cabin a second time with a cloud of terrible-smelling smoke (trust me, the electrical-wire-smoke smell isn’t pleasurable to say the least), I confirm, at least, I have a problem, and it isn’t with the wiring.
Over the past few years, I’ve learned a lot working on older trucks, and one of those important things is how to “jump” over the problem to isolate it. For example, I have a set of jump wires I use to bypass things to isolate what the issue could be.
This serves me well as I setup up a jump wire to run power off the battery directly to the heater motor. As I put these wires together, the blower motor starts to spin.
Ok, the blower motor works. The fuse is good in the box. This means there is only one last thing to check: the switch.
Located behind the dash, the switch is a simple item that regulates the power being sent to the motor. For example, I have a three-speed motor, and the switch has three settings. Depending on which setting I have turned on, the fan spins appropriately.
Removing the dash panel and finding the switch isn’t too hard. I’ve done it several times by now. Examining the switch, it’s pretty clear this is the problem. The freshly burnt electrical tabs tell me this switch is likely blown.
Now, I could test to see if this switch is really burnt, and I probably should. But I’ve learned, if it’s an old part, I’d rather have a new one anyway. This is the original switch, making it a 50-year-old-plus piece of electrical equipment. The odds of it still being good are pretty poor.
Looking for a switch from Eckler‘s Chevy Truck magazine, one of about five different parts companies I use, I can find the switch for about $45.
Simple fix, buy and swap them out, but (and there’s always one of those) that’s not the only issue. The Swiss cheese firewall is a concern, and I’d really like a set of gaskets for the heater box. Also, I’d like to put in a 190-degree “winter” thermostat to get hotter fluid to the heater box. And I accidentally nearly snapped one of the bolt holes on the thermostat housing a few years ago. I was able to “fix” this with some blue RTV gasket sealer. This should be replaced as well.
Oh, and the fuse box is starting to have some issues with certain fuses not working at all anymore. I should replace this as well.
That, then, is the real problem with an older truck: the rabbit hole you go down fixing one problem. In my head, I’m at more than $200 to fix getting heat into the cabin to replace what is probably a $2 switch to make. My list now includes gaskets, firewall cover, thermostat, thermostat cover, etc. This doesn’t include the upgraded heater box I’ve been looking at from Vintage Air.
The real question now is: How important is heat, and can I live without it? Yeah, those are real questions you ask. I’ll probably drag my feet until I start freezing my butt off and place the order. And I’ll probably mutter about the cost for a few months.
Damn old trucks sometimes.