91 crewcab, relay on driver fender? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

v30crewcab · 01-18-2018, 11:34 PM

working on a 91 crewcab 454 truck for a friend, it has single headlight, and we are putting a dual headlight front from a 89 suburban on it. it has a relay on the driver fender, near the hood spring, that the wires run into the lighting harness. the 89 suburban has the same relay, but it is wired into a different harness instead of the headlight harness. it is a 6.2 diesel suburban. what does it run, and why are they wired different? I've looked thru the factory 89 manual but can't seem to find any info on it.

Wwes · 01-19-2018, 09:23 AM

That should be the daytime running light relay.

You should be able to find it in the wiring diagrams at the link below: http://67-72chevytrucks.com/vboard/s...d.php?t=545416

Edahall · 01-19-2018, 09:24 AM

On a 6.2 diesel, that relay is for running the glow plugs. It must have been added on your truck with the gas motor.

v30crewcab · 01-19-2018, 10:16 AM

the glow plug relay is on the back of the engine on the driver side on a 6.2. I found it in the 91 wiring diagram, but not on the 89 diagram. drl wasn't functioning on the 91, and we don't need that anyhow, so I guess I won't worry about it too much, but I want the 89 suburb to function so gotta figure out what its purpose is on that truck.

83GMCK2500 · 01-19-2018, 03:12 PM

Is it for the horn? Horn wiring is in the same loom as lighting...

wildwilly4x4 · 01-20-2018, 06:23 AM

That is the relay for the auxiliary cooling fan behind the grill

**hatzie** · 01-20-2018, 09:08 AM

The horn relay is inside the cab.

My best guess is the DRL relay. The 7.4L engine had an AUX cooling fan.
According to the wiring manual both relays are mounted side by side on the LH inner fender.

01-18-2018, 11:34 PM	#1
v30crewcab Registered User Join Date: Apr 2012 Location: Chatt Tn Posts: 982	91 crewcab, relay on driver fender? working on a 91 crewcab 454 truck for a friend, it has single headlight, and we are putting a dual headlight front from a 89 suburban on it. it has a relay on the driver fender, near the hood spring, that the wires run into the lighting harness. the 89 suburban has the same relay, but it is wired into a different harness instead of the headlight harness. it is a 6.2 diesel suburban. what does it run, and why are they wired different? I've looked thru the factory 89 manual but can't seem to find any info on it. __________________ 88 military v30 crewcab shortbed 5.9 cummins, nv4500, 205 86 k30, 89 diesel burb, 76 gmc pathfinder 71 longbed 5.3 4l80 http://67-72chevytrucks.com/vboard/s...d.php?t=522535

01-19-2018, 09:23 AM	#2
Wwes Registered User Join Date: Apr 2017 Location: FL Posts: 144	Re: 91 crewcab, relay on driver fender? That should be the daytime running light relay. You should be able to find it in the wiring diagrams at the link below: http://67-72chevytrucks.com/vboard/s...d.php?t=545416

01-19-2018, 09:24 AM	#3
Edahall Registered User Join Date: May 2011 Location: Goliad, TX Posts: 672	Re: 91 crewcab, relay on driver fender? On a 6.2 diesel, that relay is for running the glow plugs. It must have been added on your truck with the gas motor. __________________ 1990 ¾ ton 4x4 Chevy Suburban -Cummins Diesel - 12 valve - factory rebuilt -6 speed bullet proof manual transmission - NV5600 -Gear Vendors Overdrive - HX35 Holset Turbo -NP205 iron transfer case -3.73 gears -2" Lift

01-19-2018, 10:16 AM	#4
v30crewcab Registered User Join Date: Apr 2012 Location: Chatt Tn Posts: 982	Re: 91 crewcab, relay on driver fender? the glow plug relay is on the back of the engine on the driver side on a 6.2. I found it in the 91 wiring diagram, but not on the 89 diagram. drl wasn't functioning on the 91, and we don't need that anyhow, so I guess I won't worry about it too much, but I want the 89 suburb to function so gotta figure out what its purpose is on that truck. __________________ 88 military v30 crewcab shortbed 5.9 cummins, nv4500, 205 86 k30, 89 diesel burb, 76 gmc pathfinder 71 longbed 5.3 4l80 http://67-72chevytrucks.com/vboard/s...d.php?t=522535

01-19-2018, 03:12 PM	#5
83GMCK2500 Registered User Join Date: Sep 2009 Location: Beaverton, OR from WA State Posts: 1,515	Re: 91 crewcab, relay on driver fender? Is it for the horn? Horn wiring is in the same loom as lighting... __________________ Devin 1983 GMC High Sierra 2500, 4x4, RC/LB, 400 S.B., SM-465, NP-208, Corporate 10 bolt & 9.5" 14 bolt 1996 GMC Sierra SLE 3500 DRW, 4x4, EC/LB, Vortec 454, NV-4500, BW-4401, AAM 925 & AAM 1050 1997 GMC Sierra SLT 1500 4x4, Z71/F44, EC/SB, Vortec 350 My Introduction with my '83s History New Daily, the '96

01-20-2018, 06:23 AM	#6
wildwilly4x4 Registered User Join Date: Aug 2009 Location: Sunray,TX Posts: 251	Re: 91 crewcab, relay on driver fender? That is the relay for the auxiliary cooling fan behind the grill

01-20-2018, 09:08 AM	#7
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: 91 crewcab, relay on driver fender? The horn relay is inside the cab. My best guess is the DRL relay. The 7.4L engine had an AUX cooling fan. According to the wiring manual both relays are mounted side by side on the LH inner fender. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.



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