Author Topic: Dual Tank Dashboard Switch 84 K30  (Read 10540 times)

Offline Takilma

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Dual Tank Dashboard Switch 84 K30
« on: March 15, 2015, 09:46:56 PM »
So in case anyone finds their dashboard tank switch to be DOA (see picture for example of switch) it can be replaced with an ordinary "double pole, double throw, MOMENTARY" switch. Examination of the OEM switch reveals that all it does is connect the pink wires to the green wires in one direction (left hand tank) and reverses "polarity" on the same connection in the other direction (right hand tank). Connect pink wires to center pins of DPDT switch, green wires to one pair of "outboard" pins. Make "jumper" wires from other set of "outboard" pins that connect to the pins with the green wires making sure that they CROSS over side to side. Most of you are probably laughing at this simple post, but hey, I had to noodle this up for myself and maybe someone out there is also scratching their cabeza. One more thing, I had to make a cover plate to mount the toggle switch and cover the rectangular hole in the dash, so not for the show crowd...
this whole deal is just to save bucks.

Offline Irish_Alley

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #1 on: March 19, 2015, 12:03:26 AM »
some pictures might help. i just took mine apart a couple months ago and im confused on what your saying. i understand how the stock one works but idk what youre talking about. maybe im just tired lol
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline Takilma

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #2 on: March 19, 2015, 10:42:42 AM »
Irish,
Here's a rudimentary drawing. If you find it more confusing than helpful, let me know and I'll try to make a better one...

Offline 87max

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #3 on: March 19, 2015, 06:32:27 PM »
last I knew there was repops being made of these, I bought one a few years back.
88 R30 lb7 transplant in progress
04 E350 6.0 studded & tuned work van
98 Taurus beater

Offline Shifty

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #4 on: March 19, 2015, 06:41:54 PM »
last I knew there was repops being made of these, I bought one a few years back.
Standard Ignition makes the momentary version p/n# DS293 for 81-88, and DS455 for 75-80.  For the one that isn't momentary, like my 87, the A/C Delco p/n # is D7089C.
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline Irish_Alley

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #5 on: March 19, 2015, 09:03:12 PM »
thats how the stock one right? i understand how that works but im just not sure about what youre talking about. got any info on the switch youre talking about?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline enaberif

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #6 on: March 19, 2015, 09:21:40 PM »
These switches are nothing more than a DPDT switch which you can pick up in any electronics store. The only thing that makes them unique is the bezel around it.


Offline Irish_Alley

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #7 on: March 19, 2015, 11:02:08 PM »
lol ok now i understand. before your first picture looks pretty much how the stock one works thats what confused me.
but do you have a ideal how to make this work with the 75-80 style they have 5 wires

i dont know anything about them.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Takilma

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #8 on: March 20, 2015, 11:33:18 AM »
Irish,
I see you are dealing with a "whole 'nuther" switch than I have. You can still work up a replacement. Use an ohm meter or a battery powered test light and "map" out your switch. I realize that since your switch is probably bad, you won't be able to get connection on all pins/positions but try holding the switch on real hard, maybe some contact cleaner sprayed in it will help it. You will find it either is a conventional switch like enaberif's diagram...or it is doing a "tricky" crossover thing like Takilma's drawings. Either way, a "garden variety" switch will do the job.

Offline Takilma

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #9 on: March 20, 2015, 11:49:10 AM »
Here's a pretty good set of wiring diagrams courtesy of CaptKaos buried in this very forum.
Unfortunately, looking through them, I see nothing about dual tank switches...


http://forum.73-87chevytrucks.com/smforum/index.php/topic,11766.0.html

Offline Irish_Alley

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #10 on: March 20, 2015, 11:31:46 PM »
lol no i have the first one you posted. i dont know anything about the other style just knew they had a couple different styles
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Irish_Alley

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #11 on: March 24, 2015, 10:56:44 PM »
found this courtesy of hatzie
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline hatzie

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #12 on: March 25, 2015, 06:03:46 AM »
^^^^   That's the 73-80 5 contact rocker switch
It's just a Double-Pole Double-Throw ON-ON rocker switch that's missing one terminal to key the connector so it can't be plugged in backwards.  The single terminal solenoid valve is only energized when the switch selects the AUX tank so the 6th terminal is not needed.  The 73-80 tank switch also switches the gauge directly at the dash.  You can use an ON-ON DPDT Toggle switch rather than the GM rocker by cutting off the 6th terminal.

81-91 motorized valve system...
I'm not sure why GM chose to use a three position Momentary-OFF-Momentary Double-Pole Double Throw Polarity reversing switch on the 81-86 trucks.  The 12VDC motor driven Pollack valve has an internal limit microswitch and diode arrangement that shuts the motor off once the valve shuttle reaches the end of its' travel.  The 87-91 RV series trucks use the AC Delco  D7089C two position ON-ON DPDT polarity reversing switch.  When the Momentary style switch fails... you can and should pitch the 81-86 style switch in the bin and use the 87-91 style switch on the 81-86 trucks.
The 81-91 Pollack valve handles the gauge select function with a second microswitch internal to the valve. 
Attached is a drawing that shows the function of the valve and two position DPDT Polarity Reversing ON-ON switch.  I left out the OFF resting position of the 81-86 switch.




« Last Edit: March 25, 2015, 06:34:30 AM by hatzie »
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC

Offline hatzie

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #13 on: March 25, 2015, 06:24:05 AM »
This is a graphic of the internal function of both switch styles.
The LH pane is the Polarity reversing switch the RH pane is the 73-80 DPDT 5 terminal switch.
I'm trying to demystify the internal workings of the dual tank systems a bit...
« Last Edit: March 25, 2015, 06:38:11 AM by hatzie »
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC

Offline hatzie

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Re: Dual Tank Dashboard Switch 84 K30
« Reply #14 on: March 25, 2015, 06:46:15 AM »
Here's a pretty good set of wiring diagrams courtesy of CaptKaos buried in this very forum.
Unfortunately, looking through them, I see nothing about dual tank switches...


http://forum.73-87chevytrucks.com/smforum/index.php/topic,11766.0.html

Those are Haynes or similar one-size-fits-all wiring diagrams.  They're OK but they're missing a bunch of optional equipment wiring detail that's in the GM manuals.
Chris posted copies of the scans I made of the GM service manuals.  They include year specific wiring diagrams that do include the RPO NL2 wiring diagrams for each year.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=25639.msg213706#msg213706
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC