Hello All,
I'm hoping someone can help me with a vexing problem.
This started out with the heater fan not working. Tracing wires, continuity checks, voltage checks, etc. come to find out heater switch not getting power. Run new wire from #16 fuse to switch. Have fan, no temperature control. Brrrr. Dig deeper into wiring. Find hack "repair" with a butt connector that caused initial problem. Fixed that and now have fan AND heat. YAY!!! BUT...
In moving around fuse/relay board I managed to bring the Prince of Darkness to my headlights.
What I have determined is that the Light Relay is not being energized and so is not passing current to the headlights and parking/tail lights. Park/tail/instr lights work in first position of headlight switch but NO headlights/park/tail/inst. lights in second position.
My Qs:

1. Can someone direct me to a good wiring diagram for a 1992 740? I have one for a '90 740 and a '92 940. Both helpful but not exactly correct.

2. Where do the yellow/white wires off the side of relay go? One heads to the fuse for rear foglight if I remember and the other goes into the BIG bundle heading into the jungle under the dash. This is wire is the one I suspect.

3. If I'm wrong in #2 can some tell me which wires to trace/check for closing the relay. I have power in the big RED wire but nothing to the yellow/whites. Currently (NPI) I'm jumping the relay to get headlights and putting the headlight switch in the first position to get tail/parking/ instr. lights.

I look forward to your replies and THANK YOU!!! JB

JB,

Here's a diagram for a 1991 - gotta be pretty close in configuration:

http://www.volvowiringdiagrams.com/volvo/740%20Wiring%20Diagrams/Volvo%20740%201991%20Wiring.pdf

Scroll to the third page from the end so that you can see locator A-B 27.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Hi JB,

Found a wiring diagram for 1992 Volvo 740 (sedan and wagon?) at:

http://www.v8volvo.se/mekartips/volvo/
(Bookmark this page, huh?)

Specifically, the PDF file:

http://www.v8volvo.se/mekartips/volvo/Filer%20740/Volvo%20740%201992%20Mitchell.pdf

This file is the same variety and published as those on:

http://www.volvowiringdiagrams.com/?dir=

Maybe look at Dave Barton's page on Volvo relays:
http://www.davebarton.com/volvorelays.html

The Volvo 740 / 940 / 90 have the (### $$ XXX !!!!) combined relay and fuse platform platform. In your 1992 740 it is behind the ashtray. The item requires service at 25 years of age by removing it, inspecting connections underneath, and using DeoxIT at all connectors to over come corrosion.

www.caig.com

Relays can fail, or, more likely, where the relay pins secure in the slots on the relay board are merely not making contact. Heat forms at corroded bonded connections. It is likely you'll find the replay board warped or worse, from heat at the headlight relay and even the fuel pump relay.

As for diagnosing a wiring job hack at a distance is difficult.

I hope the wiring diagram helps.

Earl Grey Tea Boyeeeeeeee MacDuffy's Tavern.
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