Column update (early column to late column with dimmer, wipers)

[slotard]

I was wondering whether swapping in a newer column with more modern features (wipers mainly, don't care where the dimmer is) is reasonable. I understand I'd have to do some custom wiring but hopefully not everything.

My wipers are moving especially slow so I need to go figure out why, I can swap the motors if needed.

Has anyone done this?

[Matt Man]

Would like more info on this as well.

[esbstuff]

Its easier to just add delay wipers to your truck... just change the switch and you are good to go...

On your motor try cleaning the connections and grounds first, but more than likely you need a new wiper motor.

[ray_mcavoy]

In 1978 GM changed these trucks over to a new design permanent magnet wiper motor with an externally wired park switch. That resulted in some changes to the switches & wiring.

The older 73 - 77 wiper motors will not work correctly with the 78+ switches. To use a 78 or newer switch, you also need to change to a 78 or newer wiper motor (I believe they still bolt up the same). And you'll need to change the wiring to match.

[1774btcrew]

I would really like to know what is involved in wiring in one of the newer motors. If it is just involving cutting off one plug and splicing another one on, it wouldn't be too bad.

[ray_mcavoy]

Yes, I suppose it could be done by splicing on different plugs (at both the motor & switch). The externally wired park switch in the 78+ motors also requires an extra wire to be run between the motor & switch. And the wire color coding is different so you'd have to keep track of what wire you splice where so they match on both ends.

Another alternative would be to remove all of the wiper wiring from a 78+ donor truck and transfer it over into the 73-77 truck that's being converted to the newer style motor. This could be done without cutting or splicing any wires by extracting the terminals (wires & all) from the bulkhead connector. The engine compartment side probably wouldn't be too bad since the wiper motor wiring is mostly out on it's own & easily separated from the rest. But the under-dash side is bundled / taped together and would be a bit harder to extract. I believe the connectors are different for the 78-83 dash mount switch vs. the 84+ column switch so you'd have to factor that into your donor truck search. Also, I think it's 85+ that have the electric washer pump mounted in the reservoir (instead of the mechanical pump driven off the wiper motor).

This 2nd method would definitely be more work extracting & swapping all the wires. But I think the end result would be a cleaner installation without any splices. And should a person ever have to do any troubleshooting, not having any inconsistencies of one wire color spliced to another would make that process easier.

[slotard]

I'm not sure mine even has washers at this point. With no snow here it isn't too important.

[hatzie]

One thing that's worth noting is the intermediate shaft from the rag joint to the column end will need to be changed to match the new column. Good time to do a Jeep XJ U-Joint shaft swap.

This is what I posted on another board about the electrical part of this swap...

I thought about doing this a while ago because the 85+ tilt columns are a bit easier to find and the later Pulse wiper setup seems a bit more robust.
You could move the dimmer to the column too but you don't have to. It's three wires. Power from headlamp switch, Low Beam and, High Beam.

The turn, brake, hazard, horn and, "ignition key inserted switch" harmonica plug will need to be changed from the 73-77 cab harness harmonica plug to the 78 and later piece. There are a couple different harmonica plugs between 73 & 77 so get your wiring diagrams and the diagrams for the donor. 78 to at least 86 were the same and I believe all the way to the end in 91. Chase the wires using the GM circuit #s. GM was consistent about the circuit #s in the wiring diagrams across multiple years but not the wire colors on the chassis.

As Ray noted the 73-77 wiper motor will need to be swapped to a 78-80 motor.

Wire #6 on the 73-83 dash wiper switch is the panel lamp. You don't need it...

GM uses a switched ground system on all of their wiper motors on this series of trucks.
There are no 12v power leads on the wiper switch contacts.
The wiper switch routes grounds to the wiper motor not power.

The wiper motor has constant ignition power from the WIPER fuse on two circuit 93 leads. Washer and Motor.

The optional CD4 delay option is plug N play after 1978. It's a matter of buying the module and switch and plugging them in.
The 1978-1983 wiper plug from the cab harness plugs directly into either the 2 speed wiper switch or the pulse module and switch with no changes.
The 1984-1991 Pak Con 12020492 wiper plug from the cab harness plugs directly into either the 2 speed wiper switch pigtail on the column or the pulse module with no changes.
The difference is the additional control wires between the pulse module and the wiper switch and the potentiometer in the wiper switch itself.
According to the schematics 1984 used a three wire control. 1985-1991 used a 2 wire control. I've read you can use the 85-91 modules with the 84 switch and wiring so I wonder if the 1984 CD4 schematics may be wrong.
The Pak Con I 12020492 connector shell is obsolete but the individual terminals # 12040508 are available from Mouser etc...

Circuit #s and functions will be valid for all diagrams from 78-91.

1973-1977 do not have a Park Ground so are incompatible with either of the 78-91 Pulse wiper controllers and motors.
1973-1983 have dash mounted switches with panel illumination bulbs.
1984-1991 have column mounted switches with no illumination.
1985-1991 wiper motors no longer have the washer integrated into the motor.

ON THE SWITCH
---------------
ON PULSE SWITCHES ONLY

1978-1983 (1984?)

901 Pulsed Ground to Low circuit 91
902 Potentiometer Wiper
903 Potentiometer Element

(1984?) 1985-1991

96 (two connections to pulse box) Loop up through the Potentiometer Wiper and Element and back to the pulse module.

ON BOTH SWITCHES

94 ground out to motor Wash
150 ground
92 ground out to motor Hi
91 ground out to motor Low and Park Low
97 OFF Ground out to (Park) (this connection is not present on 73-77 wiper switches)
8F variable power from dash lamp rheostat for switch illumination ONLY. This does not route to the switch contacts and is not present from 1984 on.

-----------------

WIPER MOTOR
-------------
PARK SWITCH

97 Ground from OFF switch (this connection is not present on 73-77 wiper motors)
91B Ground from Low switch

WASHER

94 Ground from Wash switch
93B Washer Power from WIPER fuse

MOTOR

92 Ground from Hi switch
91A Ground from Low switch
93A Motor Power from WIPER fuse

Wiper wire color by circuit and year.