1990 740 GL Non-turbo w/ Bosch Ignition System
While attempting to clean the corrosion from my radio suppression relay connector, the old "insulation sheaths" that fit snug inside the connector housing (around the female pins / wires) had rotted out completely & fell to bits... so the wires have now slipped out of the housing & are dangling loose. I have no idea which relay pins go to which colors / wires. I did find a wiring diagram for my car in the forums here... problem is, I cannot make heads nor tails of these intensive diagrams, or read them properly. Also, the wire colors don't seem to match mine?!
I am attaching a more simplistic diagram I found for "connector shape" reference -- my wire colors don't match these!
My wire colors are: RED, GREY/RED, BLUE/BLACK, GREEN/BLUE -- (fyi there is a tiny black "box" between the 2 relays with wires going out -- is this a ground? The RSR's blue/black wire meets up with one of these wires.)

Would someone be kind enough to upload a photo of their RSR connector with the wire colors showing?
Or if anyone will advise on wire-to-pin colors, it would be greatly appreciated!
Again, my car is a '90 740 non-turbo bosch system (NOT Regina)-- relay is located under the hood, RH side, perched in front of the coolant reservoir (next to the fan relay)
MANY THANKS!

 

those colors concur with the greenbook for 1991 (I don't have the 1990 book, but it should be the same).

pin 86 (1) is black, and is direct to ground.
pin 85 (2) is blue with a yellow stripe, and is the control signal from the fuel pump relay under the console
pin 87 (3) is green w/ red stripe, and is the power to the fuel injectors
pin 30 (4) is solid red and is the power directly from the battery plus.


if you have a volt meter, the red wire should always be powered (+12V), even when the car is switched off.

the blue-yellow wire is powered (+12V) when the ignition is switched on.

the black wire should be 0 ohms to ground.

if you unplug an injector, ONE pin of the injector plug should be 0 ohms to the green/red wire (do this with the car switched off!). the other pin of the injector may be some random resistance or open.

 

Hi, Pierce! Thanks so much for the reply!
Problem is, my wires don't match the ones in that diagram...
My wire colors are: RED, GREY/RED, BLUE/BLACK, GREEN/BLUE
Attaching a few pics for you. Any advice? Thank you!

 

what i said, test them with a volt meter. the soldd red heavy one is almost certainly the +12 power from battery. and the blue/black is probably the ground....

WAIT a second, that LEFTmost relay in your 3rd picture looks like the RSR relay, look at the wire colors.

the COOLING FAN relay has blue-green (pin 1) , blue-black (2), red (3), and grey-red (4)

acid test, with the car off, touch the red wire to the grey-red one, and I bet the electric cooling fan comes on.

 

WHOA!!!
I must've misidentified the RSR (by using another online volvo forum user's diagram!) Eeek!
Touched the wires together as you suggested, but fan didn't come on; HOWEVER there was a spark at the black battery cable terminal. >>Please don't tell me it shorted anything(?)

SO -- if it IS the fan relay (since wire colors match,) any idea which wires go to which pins?
A million thanks!

 

if the blue-black wire wasn't touching anything, I'm not sure how it could have sparked.

pin numbers in the above post. pin 1 is also 85, pin 2 is 86, pin 3 is 30, pin 4 is 87

 

DOH! I see it now & I've got it!
Thanks again for your help, Pierce.
Ran out of daylight, but will be up & at it again tomorrow. The rotted "sheaths" from inside the connector housing (that are now missing) might cause an issue, and I'm having a problem finding any replacements online -- and furthermore in finding any replacement connectors/harnesses w/ pigtails, if I should end up needing one. And I'm sad to say that it looks like the true RSR Relay ALSO has rotted-out sheaths!
Thought I might just use some electrical tape around the connector wires to help snug them in the housing -- good idea or bad idea???

Wondering if you or anyone here has any pig-tailed harnesses/connectors to sell? Or a source online for buying them, or just the neoprene-looking sheaths themselves? Saw a really neat fix that someone did with aquatic fish-tank tubing & JB Weld! Not sure I'm confident enough in my abilities to swing that, but might just have to try it if all else fails. Wish me luck!

 

here's the connector housing,
Volvo Harness Parts

and the female 3.5mm bullet connector pigtails, he's selling these as the connector preattached to 24 inches of wire.
Volvo Harness Parts

I would cut maybe 1-3 inches off the original wires to get clean wire and insulation, and cut these new pigtails down to the same few inches, and splice them on with waterproof marine crimp splices. use a good crimper and crimp them well.

 

oh, be sure to get the fat red and fat yellow/blue pigtails... splice the yellow/blue to the grey-red wire from your harness, as thats carrying the fan power. the other two, blue-green, and blue-black, can be regular/skinny gauge (use green, and black respectively so there won't be confusion).

 

Fantastic! Thanks for the info!
Fresh eyes today -- Just tested the red to red/grey again, and sure enough, just as you predicted - the fan came on!
My old analog meter has apparently bit the dust - will have to invest in a new one.
Since I can't get a volt reading to be sure... one quick clarification about reconnecting the Aux Fan Relay ... If the blue/black wire is the Ground, shouldn't it go with pin #1 ?
Your previous post said, Just want to be certain. Much appreciation!

 

blue-black is grounded only when the fan is supposed to turn on, either by a pressurestat on the a/c, or by a thermoswitch on the radiator. this goes to pin 2 aka 86 (coil ground)

blue-green comes from switched power via fuse 9, goes to pin 1 (85), this powers the coil side of the relay

red is direct from battery, to pin 3 (30), to the switch side of the relay

grey-red goes to the fan motor, from pin 4 (87), from the switch side of the relay.

 

(for anyone else following along, note that in 1992, the 740/940 fan wiring CHANGED SIGNIFICANTLY, it uses a different dual relay, and has a dual speed fan!)

 

Brilliant! Most sincere thanks!

 

I'm well and truly too late.
HOWEVER,
I did see "on this forum" a suggestion to simply pull both relays and swap them.
I did this and
one other thing which was to
remove and thoroughly clean the coolant temperature sensor, replace it and ensure the correct harness wire is installed to it.
This will fix most problems to do with cold start, fuel run injectors, and also make some great soup.
It may kill the condensor aux fan. This is not a major problem but must be rectified.
You can soak the wire ends in white vinegar overnight to tidy up the oxidation.
You may need to buy a new relay from IPD.
IPD will assist with the wiring colours arrangement I'm sure.

On doing these two things my car started "pop" and does so every time.
Nothing else I did fixed the problem of no-start -
these things I did include
(in no particular order)
replace throttle position sensor, (happened to have a new one)
replace the Idle Air Controller (not new!),
replace the MAF with another (not new!),
replace the cold start injector, (not yet done the O2Sensor replacement but have a new replacement part),
ensuring airtight air flow for crankcase ventilation pipes,
replace fuel pressure unit (non-electrical) (not new!),
replaced distributor cap and leads and coil (all new),
NGK plugs,
tore out 4 (four) patches of hair,
replaced external fuel pump and filter (both new) ,.

Ensure ALL connections are clean.

This will fix most problems to do with cold start, fuel run injectors, and also make some great soup.
It may kill the condensor aux fan.
You can soak the wire ends in white vinegar overnight to tidy up the oxidation.
You may need to buy a new relay from IPD.
IPD will assist with the wiring colours arrangement I'm sure.

I do not expect a single problem from this motor for 100,000 miles (or 160,000 kilometres here in my home region)
I also did the cam belt, seals, and tensioner roller, replaced fan belts and set correct tension ( if you have instrument panel problems like dead odo, speedo wonky/dead) FIRST try tightening your alternator belt to a correct measure.
I was going to replace the gear cogs in the odo speedo , bought the cogs, and after tightening the belt for the odo the speedo/odo is dead accurate and totally reliable ... believe it or nuts.

These things improved fuel consumption by 30+% over what was there previously.
Motor is a smooth and purring like a tight, strung, *****, cat.