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There is a silver metal housed relay behind the brake booster that has started buzzing. I looked through the wiring diagram but have not been able to find it. Anyone know what the relay controls? While we're at it, what is the black one control also.
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1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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I don't think you have in tank electric pumps, so I would guess the Trailer Lamp Relay.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold 1992 Bronco XLT 4x4 351W E4OD 1998 GMC Sierra SLE K1500 350 4L60E Arizona |
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The trailer light relay shows in an illustration here: http://www.garysgaragemahal.com/trailer-option1.html.
Big Blue has the aux battery solenoid, which is the shiny unit in the pic below, as well as the fuel pump relay and the trailer lighting relay, shown to the right of the aux battery solenoid. ![]()
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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In reply to this post by donaldb
For all electrical devices, ID them by their wire colors. Post pics. The most-important wire (for ID) on a relay is the little one that triggers it to change state (on/off) since that identifies its function. |
In reply to this post by donaldb
Behind the brake booster, do you mean on the firewall inside the cab? What is the shape of the relay?
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold. 1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021. 1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995 |
In reply to this post by donaldb
Pictures added
1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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I suspect the black one is the trailer lights relay. But don't know what the silver one is. We need to know what the wire and connector colors are going to both of those relays. And each wire should have a solid color and a secondary color, but you may have to uncover the wire from in a covering to be able to tell the colors.
Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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My 1984 FSM only shows two possible relays in that location. Trailer Lights Relay: ![]() Or the Marker Lights Relay, which was supposedly only on the DRW trucks: ![]() ![]() However, that's from my '84 FSM...could be different stuff included in 1985 for sure. Snagged this picture below from FTE, also from a 1985, and it was clicking, but the guy was trying to diagnose a no start issue, and the clicking silver relay was never identified. ![]() That's my 2 cents while finishing my morning coffee. Not much help, I know.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold. 1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021. 1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995 |
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He hasn't said what engine he has so could it be the choke relay for a 351 4V engine? the 1986 EVTM shows a group of relays in the 5.8L 4V carburetor circuits but isn't clear on their locations.
Bill AKA "LOBO" Profile
"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413 |
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I had wondered that as well, but there appears to clearly be a black/yellow wire in the pic and I can't find it in any of the EVTM illustrations I've looked at. Here's the carb ones:
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Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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In reply to this post by 85lebaront2
I think Lebaron nailed it...
If you do a search on choke relay, a couple different old threads pop up, and they're all in reference to a 351 4bbl engine... Pics of the same relay in this thread below: https://www.ford-trucks.com/forums/1146787-carb-choke-problems-2.html ![]()
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold. 1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021. 1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995 |
Interesting, the factory carb has been replaced with a regular Holley, requiring 12v for the choke. The relay in question I would guess with pretty good confidence is factory since it is using the same color and shape rivet to hold it on as the other one. If it warms up in Missouri today I'll see if I can get the wire colors.
Thanks all who commented.
1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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In reply to this post by Rembrant
First, what do those yo-yos on FTE know?
![]() ![]() Ok, so it is probably the choke relay, although there does seem to be some discrepancy with the wire colors - both in the FTE thread as well as here. Further, the EVTM contradicts itself. The schematic above is from the 1985's page for 5.8L carb circuits in the Electronic Engine Controls section. Note that it says the connection goes to Page 15. The schematic below is from Page 15, and it clearly says only the 4.9L engines have a connection to the carb circuits on the Electronic Engine Control page. All else go directly to the choke. Hmmm, can't be both ways. But, let's assume that's what it is. Then why is the relay buzzing? I'd say there's a problem with the alternator's stator output. If you look at the schematic you'll see that the stator isn't grounded, and that it relies on the diodes. I think one or more of the diodes are blown. ![]()
Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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Gary think you are right about the diodes. Is the diode set replacable on Gen 1 alternators?
Thanks
1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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Yes, it is. But you might want to upgrade to a 3G.
Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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This post was updated on .
In reply to this post by donaldb
donaldb, photo those wires and connector if you can.
Vinny...
"Do All Scheduled Maintenance Prior To Troubleshooting"
"Resolve All Known Issues Prior To Troubleshooting"
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Finally warmed up to get out there and look at it. It is exactly as Gary's wiring diagram shows above. 2 black ground wires, Yellow, gray with with white, and white with black.
Thank you all for the help Donald
1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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Welcome. Have you figured out why the relay was buzzing?
Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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As you said alternator.
1985 Ford F150 XLT Lariat, 5.8W HO, 4BBL, 2wd, Long Bed, Red and Tan
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In reply to this post by Gary Lewis
And, more specifically, blown diodes. That would give alternating current to the relay's coil, causing it to alternately pull in and then drop out, creating a buzz. Thanks for confirming the theory.
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Gary, AKA "Gary fellow": Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
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