Hi all,

Have a 1988 740 turbo wagon.

This is a strange one and I'm not sure if the 2 are related.

First: sound from the radio will come in and out somewhat randomly. The passenger side power window button usually turns the sound off and on with a static sound.

Second: there is a rapid, "electrical sounding?", clicking noise coming from within the car while driving. Sounds like it's coming from the glovebox or maybe the ecu in the passenger kick panel. The clicking speed doesn't vary with engine speed but does stop at idle.

My question: what could be causing the clicking noise?

Thank you for any suggestions.

Hi,

Finally got around to looking into my problem. Went around and cleaned all the grounds I could find: right and left kick panels, fender walls, etc., and the engine block just for fun. Also found the relay behind the glove box and cleaned its contacts up.

I'm thinking the clicking noise was the relay but I did everything at once so I'm not to sure. Definitely think the radio sound cutting out was due to bad ground(s). In any case no more clicking and I have a reliable radio again.

Thank you so much for the help and very detailed response kittysgreyvolvo and thank you as well to
jwalker.

Glad to be driving my 740 again after 3 years of it being parked!

Hi,

From k-jet.org we have a set of Volvo factory green manuals. I'm unsure whether they treat your model year 1988 740 Turbo.

See:
http://www.k-jet.org/documents/greenbooks/700-series/

Specifically:
http://www.k-jet.org/files/greenbooks/700/TP31075-1_760_wiring_diagrams.pdf

I'm unable to find a wiring diagram for 1988 Volvo 740.

http://www.volvowiringdiagrams.com/?dir=volvo/740%20Wiring%20Diagrams

Is the radio original to your 1988 Volvo 740 Turbo? If factory installed original, components inside the radio are well-aged. If a replacement, may still be a defect in the radio (or component stereo system with a radio / cassette / CD head unit, external power amp ... defect at pre-amp out to power amp in, and / or to speakers)

The passenger side power window, when you press it, having an effect on the radio may mean faulty ground connections(s) and / or faulty or poorly connection between power amp out (be it the in-dash power head unit or component stereo system - whichever you have installed).

Do all speakers turn on and off with front passenger side window power window button pressing or only a few? Have you omitted any symptoms in your description?

In the Volvo 700 (and 900)-series wiring diagrams, nearly all power routs through a fuse and relay block (or platform), usually mounted behind and below the center console ashtray. The fuse and relay block is a service item. As the Volvo 700-series designer decided to add hundred of feet of conductor to connect system fuses and nearly all system relays through this fuse and relay block, age, wire connection corrosion can cause fits for the 700 and 900 series. While you are in mostly dry Denver, the winters bring magnesium chloride as roadway ice and snow melt.

Also, as an entry in the 700-900-90 series FAQ describes, high current pass through this fuse and relay block may require service of it or replacement. The ABS plastic platform is known to warp from heat, where the fuel injection or climate control relays mount. It may be a matter of wiggling relays and pulling and replacing fuses to renew the metal to metal contact, or, replacement of the fuse and relay block with new wire harness terminals crimped at the end of the wire harness connection. A time-consuming affair, I'll guess. (I don't like the design.)

See Dave Barton's Volvo Relay (and fuse) info page for location for your model:
http://www.davebarton.com/volvorelays.html

The PDF files:
Relay Locations - 1987 740/760 (PDF)
Relay Locations - 700/900 series (PDF)

... should help you.

Two relays are behind the glove box and deal with climate control. Also, how is the HVAC blower working?

The clicking sound may relate to vacuum control of the HVAC vent flaps or dampers. I'm unsure, probably wrong, yet iirc the 740 turbo may have used an electrical vacuum pump to create vacuum to control the HVAC vent flaps or damper. The pump may be faulty? If no vacuum pump, and the HVAC vent flaps or dampers control use engine vacuum, there may be fault with the vacuum lines. If you remove the glovebox, you'll find the vacuum reservoir which looks like a white opaque or black hollow plastic body of three or four tennis balls lined up with vacuum line connections at either end.

"The clicking speed doesn't vary with engine speed but does stop at idle."

Maybe a combo of engine vacuum and a vacuum pump? I'm unsure. May look it up another time. Though you can look it up. I do not have my 700-series service manuals here with me.

Hope that helps to get the conversation started.

Questions?

Thanks,

Duffed.
--
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Hi, thank you much for the response, I very much appreciate all of the information and suggestions.

Yes it is a replacement stereo and I actually have 2 that do the same thing when switched out. With both radios it's all or nothing when the sounds quits and comes back in.

I have some reading to do :) but hopefully tommorow I will get to cleaning grounds and messing around in the fuse panel and see how that goes.

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As far as the clicking is concerned: I should maybe say it's almost a crackling sound (like cellophane?). Not sure I can describe it correctly.

Anyway. The hvac blower works normally. However, there is always air coming through the vents without the fan running while driving the car.

I will certainly pull the glovebox and see what's going on behind there.

I definitely follow your thought on what is going on and thank you much. Hopefully by midweek I will get this all sorted out and post back what I found.

Kitty could be onto something. Clean all the grounds thoroughly. The clicking makes me suspicious.

For the next poster, sandpaper and electrical cleaner should take care of it.

When you clean the grounds where are they and how will you clean?