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78 A Model restoration for daily use.

Posted By W900AOwner Friday, February 24, 2017 12:29 AM
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W900AOwner
 Posted Friday, February 24, 2017 12:29 AM
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Last Active: Friday, February 02, 2018 12:01 AM
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I'm doing my second A Model over and have a little concern as to what I'm into. I have been replacing all the crispy Aeroquip air lines with nylon. I'm in behind the dash now, and in trying to conserve time, I got it opened up as far as I can to get in with my hands. If I had more time and not on a schedule, I'd have just taken it completely apart.

I found two lines so far that I have no clue where they go. One I removed from the red trailer emergency valve about 4-5 feet long. When I tugged on it ever so gently to see about where it went, it came up out of nowhere with no fitting on the other end. I have no clue where it comes from (aside from the "T" on that red valve which I removed it myself.) The second line was unscrewed and laying in behind the 3 brake valves....a short line. No clue as to what that does either. Might be a jumper off one of the other valves...but I didn't take it off.

I bought this truck a month ago from an old timer that's been tinkering on it since 2003. I knew I was going to do some major renovations to her, which I certainly am. He had some guy take the 24V starter out and put a new 12V one in, and rewired the starter. The bigger problem was, the guy removed the series parallel switch and threw that away...and just left the 5-7 wires there for everybody to guess where they go now. I drove this thing home 250 miles one cold Sunday without a single bit of electricity going into the cab...no lights, heater, nothing. It starts, but they have it wired so the starter switch (It's a 3406 PCTA with the glow plug/starter switch + an ignition switch,) which is also the glow plug switch HOT all the time.

I did manage to decipher that I needed cab power so I located those two thicker wires and put a 50 amp breaker on the inside of the battery box and got the cab fired up anyways. I changed the ignition switch and that's new now. I still have direct power to the starter/glow switch however, so something ain't right. (Oh, there is a cheap chinese starter solenoid in the battery box they threw in for the starter too, I should mention.)

My main reason for coming on here is to ask if there's any source for a wiring diagram for these 24 to 12 volt conversions, and if there's an air line routing diagram as well? Kenworth dealer has no clue, and nothing for me on this. I am dealing with one of the last old timers at the dealer I use and once he's gone...the show's over cuz these younger fellas aren't interested in looking past that computer screen for anything I concluded.

I sure would appreciate some crackerjack's advice here for these diagrams, or something to go by so I can clean this mess up and get the heck out from behind this dash, and get to doing all the other stuff I need to be doing so I can start producing soon. I got two guys working along with me, so we're getting things done but this wiring/air situation has me waking up at night nervous.

I have some pics here of the project too. Some work details include: Replacing floorboards, cut back of cab/front of sleeper and installed Peterbilt Unibilt rings and boot for more legroom, reconfigured exhaust with a small muffler, fuel tanks relocated, new 5th wheel plate, replaced torque arms and all low pressure hoses to cans, new maxis, slack adjusters, brakes are new. Putting a Jake on off a spare PCTA I have, put a Commercial Shearing direct mount hydro pump on to run lowbed, and much, much more....

Oh,... specs are: 1978 W900A.
3406 A PCTA.
Eaton reman 15 speed.
KW 8 bag air ride.
252" wheelbase.
DS 402 rears @ 4:33
Front end has air assist. (Anyone have the setup for me to convert that to power steering, I'm all ears...)

Thanks in advance for anything you can provide...√√√

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roKWiz
 Posted Friday, February 24, 2017 1:03 PM
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Last Active: Wednesday, July 31, 2019 3:43 PM
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Hi W900,

If you use the search feature in this forum you can usually find old threads on anything W model re power steering, air, electrical systems.

I have heard swapping over to power steering on an A model to be one big headache so read everything you can before starting it.

Your two mystery lines might have supplied air to air wipers ?? if yours are electric converted or original air seat ??

here's an air schematic.

http://forums.aths.org/Uploads/Images/aa1934a8-5f2e-4def-ba4c-595f.jpg

instrument schematic

http://forums.aths.org/Uploads/Images/1c8261b2-3700-4f1b-b375-0a47.jpg

http://forums.aths.org/Uploads/Images/d5d9ab0a-29f5-496a-8e16-aac2.jpg


www.stonemasoncarver.com/Kenworthrestoration
cabover nut
In order that the labour of centuries past may not be in vain during the centuries to come...............Denis Diderot 1752

W900AOwner
 Posted Saturday, February 25, 2017 12:42 AM
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Last Active: Friday, February 02, 2018 12:01 AM
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roKWiz (2/24/2017)
Hi W900,

If you use the search feature in this forum you can usually find old threads on anything W model re power steering, air, electrical systems.

I have heard swapping over to power steering on an A model to be one big headache so read everything you can before starting it.

Your two mystery lines might have supplied air to air wipers ?? if yours are electric converted or original air seat ??

here's an air schematic.




roKWiz...I can't thank you ENOUGH for this diagram...that's a relief like you wouldn't believe.

As for those two "mystery lines", no, the wipers are still air and still in tact, and the seat was fed off the inside cab air tank that I have removed and relocating down under the truck where it belongs anyways. But at leat NOW with your help, I have something to read and go off of.

Much appreciated...√√√

http://forums.aths.org/Uploads/Images/aa1934a8-5f2e-4def-ba4c-595f.jpg

instrument schematic

http://forums.aths.org/Uploads/Images/1c8261b2-3700-4f1b-b375-0a47.jpg

http://forums.aths.org/Uploads/Images/d5d9ab0a-29f5-496a-8e16-aac2.jpg
Neddle-Nose
 Posted Saturday, February 25, 2017 5:00 AM
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I've driven and worked on trucks that had air lines that were blank on one end that were to exhaust air from valves out through the firewall instead of in the dash ??

"When contemplating advice from others it is best to stand at the front end of the horse when listening"
kblackav8or
 Posted Saturday, February 25, 2017 6:26 AM
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When it comes to air systems, when in doubt refer to the Bendix air brake manual which is freely downloaded from the web. Some of that era A models had the 3 button setup, red, yellow, blue. Nylon is the way to go for working stuff these days.


W900AOwner
 Posted Sunday, February 26, 2017 1:12 AM
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Neddle-Nose (2/25/2017)
I've driven and worked on trucks that had air lines that were blank on one end that were to exhaust air from valves out through the firewall instead of in the dash ??


That could very well be the one I have that is about 4-5 feet long that I found no end on...yes. But the short one with the 1/4" flared fitting laying there would have to be hooked to something.

And RoKWiz....I took the pics you provided here, copied them and my wife went to Staples and had them blown up. Trouble is, the got distorted and unreadable. I was going to just take my little tablet with me to work on the truck and read the diagrams off the tablet as they are clearer than the copies I made.

The irony of this is...yesterday I was in my basement and looked over in the corner on top of one of the tool boxes, and lo & behold...a KW Custom Service Manual that I totally forgotten about when I got my first A model a few years ago! Haha, it's probably the same book you took these diagrams from? It's no wonder you can't scan and email diagrams out of them, the original print isn't all that great to begin with. This book has everything tabbed in alphabetical order as it was put together.http://forums.aths.org/Uploads/Images/0e233bb6-3112-40a8-b226-7bd9.jpg

http://forums.aths.org/Uploads/Images/411b01dd-d09a-46d9-addb-be38.jpg
W900AOwner
 Posted Sunday, February 26, 2017 1:20 AM
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kblackav8or (2/25/2017)
When it comes to air systems, when in doubt refer to the Bendix air brake manual which is freely downloaded from the web. Some of that era A models had the 3 button setup, red, yellow, blue. Nylon is the way to go for working stuff these days.




That's a good piece of advice too, thanks kblack...

Yeah, nylon to me makes more sense. Much nicer to deal with than Aeroquip.

Now for another question. I am seriously contemplating putting a nice low profile roof top mounted a/c system on this truck. Who, what, where is the best place to go for that style a/c system? I like the look, and the ease of installation compared to redoing this entire thing with OEM stuff. Only reservations I have is the holes in the roof, and the extra weight up on that thin roof cap, but I know if I do things like I do them, it won't leak and will be fine. They must do something to reinforce the fiberglass roof with those units up there I'd imagine, such as a couple of aluminum reinforcement strips from mounting bolt to bolt, or something?

What's the options nowadays in this throw-away world we live in...? Kysor, Red Dot...etc?








Geoff Weeks
 Posted Sunday, February 26, 2017 10:17 AM
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Red Dot makes nice roof mount units, both condenser units and full, thru the roof AC units. They are the ones you see on the Cab of locomotives etc.
I guess it would depend on how "gutted" you system is now. I find it easyer to re build than re engineer.
Generic condensers and fittings can go a long way if the under-dash unit is still complete.
IIRC I priced out a Red Dot roof mount condenser at over a grand, a generic 32,000 BTU radiator mount type was in the area of $240, you still have to make mounts to place it in front of the rad, but a lot easyer than re enforcing the roof.
If you still had 24 volt crank, I would recommend a 24 volt Maxwell Super Capacitor start unit, it charges on a 12 volt system and lets you crank on 24. No series parallel and no special alternator required, just hook it to 12 volts and get 24 volt out of it.
W900AOwner
 Posted Sunday, February 26, 2017 10:33 AM
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Geoff Weeks (2/26/2017)
Red Dot makes nice roof mount units, both condenser units and full, thru the roof AC units. They are the ones you see on the Cab of locomotives etc.
I guess it would depend on how "gutted" you system is now. I find it easyer to re build than re engineer.
Generic condensers and fittings can go a long way if the under-dash unit is still complete.
IIRC I priced out a Red Dot roof mount condenser at over a grand, a generic 32,000 BTU radiator mount type was in the area of $240, you still have to make mounts to place it in front of the rad, but a lot easyer than re enforcing the roof.
If you still had 24 volt crank, I would recommend a 24 volt Maxwell Super Capacitor start unit, it charges on a 12 volt system and lets you crank on 24. No series parallel and no special alternator required, just hook it to 12 volts and get 24 volt out of it.
















[/quote]I have the interior gutted at the moment, so doing this roof mount would be simple enough. But I agree, so many options now to choose from that I could just rebuild what's there. The Grilldenser is still there, but no idea if it is any good still. My worst fear is the A model ventilation system isn't the best when it comes to velocity with just the two dash vents and a few small ones down below. If I could price one roofmounted in the range of repairing what I have to work with, maybe I can justify. Being I added substantial square footage with a 60" Aerodyne, I may be sorry if I depended on the OEM ductwork.... But that Red Dot headliner system I'll bet will be like a meatlocker in there.

I did away with the 24V system, It's all 12V now.

So do they offer a fully self contained unit with compressor and all, or do you use the OEM compressor off the engine to squeeze the gas? I have an existing York there now, probably no good if I were t to guess.[quote]
'











Sunday, February 26, 2017 10:37 AM by W900AOwner
kblackav8or
 Posted Sunday, February 26, 2017 11:41 AM
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Strongly consider a Vintage air setup for underdash. A couple folks have done this with vintage trucks and have found they work better then the roof mounted stuff. Probably no more expensive, maybe less.



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