LUVTruck.com

I'm in the process of removing my wire harness because my regulator fuse that keeps blowing after the truck warms up. I've narrowed it down to either it being a wire that is grounding out, or it may be two relays that have wires that go to that fuse.
I have a picture of the relays, and am wondering what they do. What are they called?
I may end up replacing them, it would at least elimanate if that was the problem.
The relays are inside this metal box near the passanger side corner of the firewall.

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

they are as 800xl would say

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My old but now gone Luv...

I messed with this until I gave up on my truck and just hardwired around some of this stuff. The 5 pole relay is for the fuel pump, the 4 prong is the (ballast) resistor bypass relay. Both need to be rated for constant on, if you choose to replace them. I think I have a snippet from a thread here on a good Autozone replacement for the fuel pump relay, but it requires changing out the base as the footprint is not the same as stock. Any decent alarm/stereo store should be able to turn you on to the correct relays if you show them the schematic. I'd been considering doing some sort of write up on aftermarket replacements for these, but I no longer have a stock truck to work from....

Good luck, hope this is some help.

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

Thanks for the info and the wiring diagram nukeday.
I got the harness reomved, I simply took masking tape and labeled each plug first. I did find a wire that came off a ring connector on the side of the alternator . I'm going to inspect the entire harness, in case someting got hot and melted the insulation.If the harness is in good shape, then I'll replace both the relays, as there is a wire that that splits from the regulator fuse and runs to both relays.

Here's the latest update on my wiring woes. I found a few spots where insulation was frayed, but it may have happed when removing the wireharness, as none of it looked like it was from heat.

I was talking to my brother about my problem. I showed him the relays. He said he just replaced some of his on his 87 Toyota truck. They make a clicking noise when they are bad.
I heard the noise before, but thought it was the starter solenoid.
I'm going to check with a Stereo shop next week about the fuel and resistor relays and then post about it.

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

Hello Zane
Did you get yours figured out i'm getting closer on mine.

The link to mine is below
viewtopic.php?f=5&t=16573

I've been chasing wires and going thru my 77
found a couple locals w/trucks and have been testing different items w/ a 12v light and meter.
what yr yours ?

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Previously owned 2 Luvs) 75 & 77 Fleet-side
3rd 77 Step fixing up aka The Yellow Submarine to Luv Ms (Sun)Shine=)
98 GMC Gas Guzzler~>The reason 4 my ~>3rdLuvNext2a66MALIBU =)
66 Chevelle The Oldest of all the vehicles I owned

I have a neighbor thats a mechanic. He took a meter and 12v light, he checked my battery, charge from my altenator, and coil. I still think it could be the relays. I went to your that link, and the wiring diagram that was drawn, made sense. I'm just waiting for some money to stop at the stereo shop and see if I can pick them up, or at least get some part numbers.

Thought Id post what the wire harness looks like when its out. I have some plus I installed so I could leave the wires that go from the firewalls to the tailights intact.
The picture is minus the wires to the tailight. I labled all my plugs, so it would be easier to install.

I still have a wire that I'm trying ot figut out what goes to it. There are two wires that come off the top of the gas pedal. The on with male end, I'm not sure what wire hooks up to it.
I did finder another wire that was nearby (solid brown wire) and I think it may go to it, but not sure. I post two white arrows to point out the two wires.
I'm posting a pic, if someone doesnt mind looking and letting me know.
Thanks!

I've posted on various electrical topics here on the board, and although I have a strong electronics background, I don't claim to be an expert on the wiring in these trucks. I hope to be, but please remember this is a hobby for me too. With that out of the way, here's what I see...

The green wire should go to the plunger on top of the brake pedal. The plunger should have a pigtail with a female connector on it.



The brown wire is part of the heater circuit. Does your blower fan work? There should be two wires coming from the blower motor itself. One of these is blue with a bullet connector and the other is black (at least this is what I had on my '78.) Black goes to ground, and blue (input power for the blower) goes to this brown wire. This may actually connect at the switch itself, but I haven't seen it this way on my '75, '78 or '79. So look this over before you connect it. Basically, there are two wires coming out of the blower casing, just above the gas pedal. One is ground (black), one is power (blue). The brown wire you have hanging should be the input power for the blower. One of the blower wires may need to be strung across the top of the heater controls. I think on the '78 the factory bullet connector was on the passenger side, I don't recall if it was power or ground, but the wire from the blower was too short to wire it any other way. You'll see in the second photo that at the switch the wire color turns from L (blue) to Br (brown).

It will make more sense when you start looking at it.





I took this from the '79/'80 wiring diagram. Hope this helps, looks like you've just about got it done...

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

Hey Nukeday,

Thanks for the wiring diagrams. First off, the brake pedal is connected correct (at least it was the way it was before), there is a plunger on the gas pedal that two green wires with male and female plug. The male plug is the one with the white arrow I posted in my last picture.

As for my blower casing. I could see the two wires (one black, one blue), the black wire goes to a black wire off the harness. The blue wire plugs in to another blue wire that goes into the back of the casing (I'm assuming that part of the motor?). The fan works, and the brown wire is not hooked up.

Is there a way you can test the relays for the fuel pump and resistor bypass relay? I actually have the fuel pump wire re-routed to the ballast reistor (it was like that when I got the truck), so I might not have to worry about the fuel pump relay?

What year truck again? If it's a Mikado, the brown wire probably supplies power to the Radio and or the light/cigarette ligther in the ash tray. The cigar lighter pulls some major current, so it's usually strung alone or with very small current loads (i.e. the radio). If I recall, the brown wires both run through the Blower fuse, so check that circuit in the diagrem. I'm at work, so I don't have time to look the diagram over, but I know there are only one or two brown wires in the whole harness. If your blower works, this brown wire must be for accessories.

The plunger for the brakes needs two green input/output wires from your harness. As for testing the relays, you need 12V DC (your battery), a couple of leads with prongs that will slip on the relay posts, and a Meter to check the output. Look at the diagram, and also the relay itself, they often show a diagram on them. Be careful if you do these checks in the truck, it's easy to drop a hot lead onto things you don't want power on (like your carb). I prefer to put a board on top of the fender and run my test leads long enough to keep them from touching anything except the object under test. Even better, if you've got a battery out of the truck, check the relays on a bench.

There are several ways to wire around the fuel pump relay, the way you've described is the most common one I've seen. On my '78 someone spliced it directly into a pigtail on the fused side of the fuse box...

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

hi i pretty sure i have mine worked out now
i compared to a working 78

In nukeday's he wrote to help me (THANKS AGAIN nukeday MY wires are now like the diagramm you shared w/ me)
FROM THE LINK

test this...on the fuel pump reply check rela unplugged

continuity between BW & BR , WR & B has a reading of 6.8

on the resistor bypass relay
BW & BL HAs continuity and 6.8 reading

NO continuity between any other combination

if you would like any other reading on my 77 PM ME
I've ran more 12v test light test and can share later when you get wires back in

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Previously owned 2 Luvs) 75 & 77 Fleet-side
3rd 77 Step fixing up aka The Yellow Submarine to Luv Ms (Sun)Shine=)
98 GMC Gas Guzzler~>The reason 4 my ~>3rdLuvNext2a66MALIBU =)
66 Chevelle The Oldest of all the vehicles I owned

Hey Zane, sorry about that last post. I missed that the green wire was the plunger on the gas pedal. I'm not sure how your heater is wired up, but this is what I found in the diagram.

It's all related to having a stock AC truck. Don't know if it's any help or not...

Purple - Green wire - Idle Speed Control
Brown - Brown wire - Heater input power
Green - Green wire - Thermo switch

After looking at your photo again, I'm wondering if the green wire has a yellow stripe? I couldn't see one...

Note: This attachment is quite large!

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

Hey Nukeday when I had the hireness out of my truck. I did the wires for continuity.
The one thing I'm not clear on is what 3rdLuvNext2a66MALIBU said:

Is this taking a relay out and putting the leads into one between BW & BR tabs (where the plugs goes onto). Was a little unclear on using the meter. Thanks!

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1980 Luv 4x4 with a 5 speed tranny.



"When all else fails, follow the directions".

Your meter should have at least 3 functions. Voltage (VDC or VAC), resistance (Ohms) and current (amps). The checks 3rdLuv is referring to are continuity, which is another name for an Ohms check. Sounds like you ohm'd out the harness already.

The way I read this is that he removed the relay and inserted his meter leads in the socket to check for an open. This is checking to see if the circuit is continuous, therefore the 'continuity check' name. In this situation, you would not want the key on or power in the circuit from any source. 0.0 Ohms, or a beep on your continuity meter means the wire is solid end to end. I'm not sure where the resistance drop is that he's described but apparently his truck is running using the checks he's done. (6.8...what? Ohms?)

When I described running leads from the battery, this was to check the RELAY itself. I don't recommend sticking a 12V hot lead from your battery in any of these connectors unless you are very clear on what you intend to see, and fully aware of how the circuit is wired.

A continuity check is much less likely to burn something up, and will clarify if the path has it's integrity. Hope this helps?!

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

If I remember correctly, the wire on the gas pedal switch activates the coasting richer solenoid when you let off the throttle in 4th gear.

Hey Zane,Nukeman sry about the unclear part/s.... In reguards to THAT Quote:
test this...on the (FPR)Fuel Pump Reply & (RBR)Resistor Bypass Relay
Check relay unplugged

1)FPR has continuity between BOTH BW & BR , WR & B & WR & B has a reading of 6.8ohms
ON THE OHMS METER (I noticed 6.7 on another relay STILL GOOD)

2)RBR BW & BL Has continuity and 6.8 reading

ZANE'S QUESTIONS?...Is this taking a relay out and putting the leads into one between BW & BR tabs (where the plugs goes onto). Was a little unclear on using the meter. Thanks!

THESE (1 & 2) WERE test on the actual relays by itself (unplugged) to confirm relay(s) are good
The wire colors are actually the POSTs on replay (where the wires would plug onto relay)

I wrote down ALL MY NOTES to comapre from one day to another IT HELPED ALOT
AS it seems like things changed from 1 day to the next
If you want me to test ANY THINg ON MINE to compare against yours
I'm WILLING to help out Please feel free to pm ?'s
I just happen to notice this one tonite I'll try to follow this when i can

My problem (I THINK ) ended up being the voltage regulator(VR) even tho it seems to charge had to have been bad AS when i switched to a solid state one the GREMLIN was gone
and stopped blowing #6 slot fuses
Hope this clears that up
MT

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Previously owned 2 Luvs) 75 & 77 Fleet-side
3rd 77 Step fixing up aka The Yellow Submarine to Luv Ms (Sun)Shine=)
98 GMC Gas Guzzler~>The reason 4 my ~>3rdLuvNext2a66MALIBU =)
66 Chevelle The Oldest of all the vehicles I owned

if it helps at all im typing up a wiring schematic that tells what wires are to go to what connection, and will include a bypass plug for the relays but this would only work if you have an electronic ignition ill go ahead and post it here when im done, it only coveers the 79/80 harness, but its kinda like a dummy guide to look at in place of trying to read the factory wiring diagram, I also have electrical issues, and there are olt of wires that i dont have hooked to anything right now that bother me and some others that probably shouldnt be hooked to where they are but all my lights work, except i dont have park then park/head light i only i to switch settings for head lights they are either on or they are on, and my blinker switch is hooked into my hazard light switch... i know its not right but i needed to stop getting pulled over when ever the cop tried to say he didnt see me use hand signals or for using them at night lol... Anyway ill post it i think its something that everyone can appreciate....

-Dustin

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My LUV - R.I.P. 1979-2009, you will not be forgotten...

Hey, what are the symptoms of a failing fuel pump relay? We've replaced the fuel filter, the fuel pump and currently tearing down the carb and rebuilding it. Wondering if a bad fuel pump relay could be at the root of our problems? Thanks!