Author Topic: 84c10 with 1990 quad blazer grill/light upgrade questions  (Read 134 times)

Offline 88rxna

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84c10 with 1990 quad blazer grill/light upgrade questions
« on: December 08, 2018, 10:40:08 AM »
hello, i am making the choice of changing out the rad support and changing over to the 1990 blazer/burb quad style headlight grill package (fromt the single headlight setup). i have sourced all the parts but the electrical side of this project.
I would like to update the wiring to feed power directly from the battery similar to the   relay upgrade. question is, what is the most practical way of doing this without spending a fortune?
is it easiest to source the harness from the burb/blazer and just get the relay package from  ? when i found the grill, i took it from a 92-95 van and took its wire harness thinking it would work but i found out it will not (due to the bulk head being different). If it would be easiest top splice into that i can. would i just find a new bulk head for the firewall connection then? or maybe de-pin the existing one?

** I do have the correct bezels, center grill section and rad support for the C10. im just not sure about the wiring yet.

Offline Da67goatman

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #1 on: December 08, 2018, 12:35:54 PM »
In my opinion it would be better all way round to make your own harness.  I don't like using 30yr old wiring that was undersized originally.  I would cut up your old harness and use the original headlight low beam wire to trigger the low beam relay and the high beam wire to trigger both relays giving you the "all on high" feature.  Pick up power from a fused battery lead (16-14awg if 55watt or more) and ground to the core support (same gauge as power wire).

Optionally:

You could use a switched trigger instead for the low beam relay and have them on with key as a running light.

Pulling power from a switched source for a would prevent you leaving them on when you get out -however parking lights would still be constant power unless you trigger them with switched power as well(not that hard)

Any questions just ask as I have the quad headlight setup on 3 different trucks each wired differently

Parts list:
*2 or 3 relays depending on weather you wanted the all on
*16-14awg green and tan for headlight relay output to new headlight
*14-16awg black for grounding each headlight and relay
*10-12awg to power all your relays and just daisy chain them rather than running each power separately
*fuse holder for power wire
optional:
*Heat shrink
*split loom
for that factory fresh appearance
<Pitcrew>
1989 R2500 Suburban mild 350 TBI 700r4 10.5" 14bolt 4.10 w/ 33s
1992 fullsize Blazer 4x4  35s no lift, 4.10s, Hella driving lights, TJ Flares, Huge bumpers, Snorkel, custom interior

Offline VileZambonie

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Offline 88rxna

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #3 on: December 08, 2018, 01:38:59 PM »
Ok, that sounds better.
So use the original harness for triggers, run 3 relays  (gonna run all on high beams) and use the 92-95 sockets for the lights?
Thank you vilezambonie for that write up! Do you have any specifics on the diode? I'm unsure about that part.

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Offline Da67goatman

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #4 on: December 08, 2018, 03:11:34 PM »
the 3rd relay is an alternate method of backfeed control in place of the diode.  You use the high beam trigger on 2 relays; one outputs to high beams and one outputs to low beams with a 3rd relay using the low beam trigger and low beam output.

if I recall correctly the bulbs will take regular spade terminals

92-95 use 9006 and 9005 bulbs and a composite lens which are completely different than the H4703 and H4701 glass sealed beams that the 89-91 used
<Pitcrew>
1989 R2500 Suburban mild 350 TBI 700r4 10.5" 14bolt 4.10 w/ 33s
1992 fullsize Blazer 4x4  35s no lift, 4.10s, Hella driving lights, TJ Flares, Huge bumpers, Snorkel, custom interior

Offline 88rxna

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #5 on: December 08, 2018, 07:32:46 PM »
i really do appreciate the help so far. i started a drawing to print out for when im ready to wire this together. i left the 3rd (diode replacement) blank because i was still unsure what to do with that.
does everything look ok so far?  Also, it doesn't matter which style headlight i go with i guess. i have both harness's from each gen so i could go either way. I guess id rather go with the one that makes more sense (has better output for the value). Id even upgrade to headlights that take a regular halogen if its cheaper and makes more sense. that i am unsure of also. making a harness i guess that i have the option to go any of those 3 directions...any suggestions?

Offline VileZambonie

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #6 on: December 10, 2018, 04:41:43 AM »
Choose whichever you like. Any diode rated for 20A will cover you.
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Offline bd

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Re: 84c10 with 1990 quad blazer grill/light upgrade questions
« Reply #7 on: December 10, 2018, 06:26:11 PM »
The diode is inserted into the relay control circuit and needs only to have a current rating great enough to safely pass the relay coil current plus a small margin.  If you are using a common Bosch style relay, the coil current is ~1 ampere.  To provide a conservative safety margin employ a 3-amp general purpose silicon diode.  Specify a peak inverse voltage (PIV) of ~400 VDC to avoid diode damage when the connected relay coil is de-energized.

The upper two diagrams, attached below, illustrate two methods of connection using a diode.  The third diagram employs an isolation relay in lieu of a diode.  IMHO the diode is the more elegant approach.  The advantage of the switch w/diode control over the relay w/diode control is that if the high-beam relay should fail or if the high-beam circuit protection opens, you will still have low-beam headlamps regardless of the dimmer position.  Other wiring scenarios are possible.

Note that in all versions of the wiring, the high-beam and low-beam relays are independently connected to B+ through separate fuses (okay) or circuit breakers (preferred).  This helps to maintain at least some headlamp function if one of the fuses/circuit breakers fails.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)