Surprise No. 238.2, and Thinking Outloud and In Writing

[Dejure]

Yeah, buying a rig nearly half way to being an antique is a pig-in-a-poke. Lots of fun things to do and undo. Things like, install the park-neutral safety switch wires, fix the washer pump, turn the wipers back into a "only on when the ignition is on" unit, install a horn, add the backup circuit (including cut wires). . . .and the heater.

That one of the previous owners wired the choke to 12 volts 24-7, and the above-mentioned, suggests they shouldn't play with volts and amps. The safe money is on, if their house has a fuse panel, it has some "fuses" that look, suspiciously, like pennies.

I didn't test the heater. The cut wire between the blower and the resistor suggests that wasn't accidental.

A quick check shows 12 volts plus at each of the terminals of the plug coming from the switch, even with it not plugged into the resistor.

SIDE NOTE: The terminals were VERY corroded. Love Harbor Freight jewelers files. They and some patience do well for cleaning contacts, and can even be used to remove the terminals for cleaning.

Any bets? I suspect pulling the switch might reveal someone swapped the 12 input from the input terminal at the switch over to the direct to the motor. Time and some testing will see.

Meanwhile, it's nice that many things on my 78 C15 are easy to get to. Things like the blower motor and resistor.

SIDE NOTE: It appears this was one of those always-on blower systems.

About forty years back, my blower switch died on my 69, so I cut and filed the switch hole out and installed a rocker that just gave me high and low. Worked for that way for years, and I didn't have to suffer the constant on blower.

Might have to look into installing a 3 position and an off-on type switch. Alternately, I could install a piece of plexi and a rotary switch for four positions (off, low, medium and high).

 

[Ricko1966]

You need to look at a wiring diaghram for your truck. The heater blower does have 2x 12v hot 1 goes to the blower relay 1 comes off the heater switch. Now certain years and I don't have them memorized the blower ran anytime the key was in the on position.

 

[ali_c20]

79 is one of the key on/blower on years.

 

[Dejure]

[OF WIRE DIAGRAMS AND SCHEMATICS]

Yep, Rick. A must. Accordingly, already well down that road. I long for schematics, in addition to wire diagrams. The former being nice, when trying to figure out switch and relay configurations. Hell, they already show us versions of resistors in the wire diagrams, so. . . .


[HANDS ON OBSERVATIONS AND SUCH]

Pulled the control panel. Then, pulled the plug off the back of the switch. The switch came with the plug.

Tested the plug with an idiot light. Got a light on all 3 terminals (at least it was only with the key on, this time). HOWEVER, I had the resistor in the circuit when I tested for power, and it was 105 and in the sun, so didn't go back and get my meter, pull that plug and see what the cab side read, voltage wise. Save that for a cooler time of the day, when it's only 95.

On that fan-always-on thing, one of the leads comes from somewhere in the fuse zone, and the other, tied to it, goes on toward the resistor. My safe money bet is on it's the low speed (again, too hot to verify).


Keep in mind, this old iron is, like too many old pieces, one of those "god, only, knows what all the previous owner(s) did" things. (Things like being able to turn the wipers on with the key off, the cut wires to washer pump, heater, back up lights, transmission cooler, . . . because, well, that's a solution to problems. No?)

OH, and the switch I pulled was full on garbage.


[GROUNDS, AGAIN, JUST TO BE SURE]

SIDE NOTE: This is one of the ground issues I hadn't thought of (the actual component grounding). Considering the condition of the terminals, it's a high probability that needs tending before I go any further.


[RE FAN ALWAYS ON]

Yeah, my old 69 was a fan-always-on rig too, until the switch died, and I replaced it with 3 position rocker (high, low and off). That was around 50 years ago. It served me very well with just those speeds, AND my many riders and I lived (not one case of carbon monoxide poisoning).

I don't know what the apes who played with this truck did, but the control panel was hammered (all fractured, and the switch mount issue, noted above).

I ordered a whole new one control mechanism. Lucked onto a 4 position option at LMC. That will allow me to leave one terminal open, to act as an off, rather than a 24-7 [while running] fan.


[FUN WITH AI "EXPERTS" (NOT) AND RELAYS NEEDED TO POWER A LOWLY BLOWER MOTOR]

SOMEWHERE, the strange claim the switch couldn't handle the blower came up. It was claimed it had to be powered through a relay. The claims cited the long run times, which comes off as ludicrous to me, since electricity really doesn't give much of a damn about run times as much as it does amperage at initial contact times (just like old points). My rocker, which was, probably, rated at 15 amps, remained undaunted by its task for over ten years.

Anyway, none of the three or four vastly different wire diagrams give suggestions of relays, so I'll stay with the simple of a switch, when I get to that point.

Makes me wonder if they were concerned about systems with air, and having to fire compressors, or something.

[STILL THINKING OUT LOUD AND IN WRITING]

 

[Ricko1966]

[OF WIRE DIAGRAMS AND SCHEMATICS]

Yep, Rick. A must. Accordingly, already well down that road. I long for schematics, in addition to wire diagrams. The former being nice, when trying to figure out switch and relay configurations. Hell, they already show us versions of resistors in the wire diagrams, so. . . .


[HANDS ON OBSERVATIONS AND SUCH]

Pulled the control panel. Then, pulled the plug off the back of the switch. The switch came with the plug.

Tested the plug with an idiot light. Got a light on all 3 terminals (at least it was only with the key on, this time). HOWEVER, I had the resistor in the circuit when I tested for power, and it was 105 and in the sun, so didn't go back and get my meter, pull that plug and see what the cab side read, voltage wise. Save that for a cooler time of the day, when it's only 95.

On that fan-always-on thing, one of the leads comes from somewhere in the fuse zone, and the other, tied to it, goes on toward the resistor. My safe money bet is on it's the low speed (again, too hot to verify).


Keep in mind, this old iron is, like too many old pieces, one of those "god, only, knows what all the previous owner(s) did" things. (Things like being able to turn the wipers on with the key off, the cut wires to washer pump, heater, back up lights, transmission cooler, . . . because, well, that's a solution to problems. No?)


[GROUNDS, AGAIN, JUST TO BE SURE]

SIDE NOTE: This is one of the ground issues I hadn't thought of (the actual component grounding). Considering the condition of the terminals, it's a high probability that needs tending before I go any further.


[RE FAN ALWAYS ON]

Yeah, my old 69 was a fan-always-on rig too, until the switch died, and I replaced it with 3 position rocker (high, low and off). That was around 50 years ago. It served me very well with just those speeds, AND my many riders and I lived (not one case of carbon monoxide poisoning).

I don't know what the apes who played with this truck did, but the control panel was hammered (all fractured, and the switch mount issue, noted above).

I ordered a whole new one control mechanism. Lucked onto a 4 position option at LMC. That will allow me to leave one terminal open, to act as an off, rather than a 24-7 [while running] fan.


[FUN WITH AI "EXPERTS" (NOT) AND RELAYS NEEDED TO POWER A LOWLY BLOWER MOTOR]

SOMEWHERE, the strange claim the switch couldn't handle the blower came up. It was claimed it had to be powered through a relay. The claims cited the long run times, which comes off as ludicrous to me, since electricity really doesn't give much of a damn about run times as much as it does amperage at initial contact times (just like old points). My rocker, which was, probably, rated at 15 amps, remained undaunted by its task for over ten years.

Anyway, none of the three or four vastly different wire diagrams give suggestions of relays, so I'll stay with the simple of a switch, when I get to that point.

Makes me wonder if they were concerned about systems with air, and having to fire compressors, or something.

[STILL THINKING OUT LOUD AND IN WRITING]

You know we have schematics in the reference library. Go to the 3 dashes top left of the page tap them then tap forums,then scroll down to reference library and one more scroll down to wiring diaghrams

 

[Dejure]

No. I did not. THANKS, Mr. Rick.

 

[Ricko1966]

No. I did not. THANKS, Mr. Rick.

Sorry I'd have told you on post #2 , had I known you didn't know that.

 

[Dejure]

The extra circuit info was helpful.

Information on the Net, including otherwise helpful videos, are all over the board on factualness, with regard to my specific debris hauler.

Elsewhere, a few were pushing the "your truck has a heater relay" thing. The premise being, the obvious fact the blower consumes the most power when running on high. HOWEVER, ignored is, for resistor systems, the same power is used in each position. It's just dissipated by the resisters, in the low and medium settings, instead of by the blower.


A.I. makes up crap too. It claimed certain rigs didn't have relays because it was handled by a resistor. Since, as noted, the same power is used by low, medium and high, this is not accurate.


In the end, the electrical info shows my rig, and hands-on experience confirms, my fuse to switch, and switch to resistor and blower wires, are only 14 and 16 gauge wires. Accordingly, the power those wires would carry is nothing any decent switch could not handle.


As it stands, all is working now. I'm just waiting for the new, purty 4 position (off, low, medium and high) assembly.


SIDE NOTE: My ramblings help me own this information, and sort through it, to fully understand this circuit. By sharing it, I hope some of it will help others solve simple issues, by way of giving a bit more info about the characteristics of some GM systems.

Hopefully, I can whittle some of this down and make it easier to sort through in the future.

 

[WebMonkey]

i know my '91 dakota w/318 had a resistor block in the firewall that handled the heater blower speed.
big coil, little coil, straight wire.

bolted into the firewall and protruded into the air duct so that it would get cooled by the flow.

same current draw regardless of of climate control switch position.


'monkey