[[email protected]]

I unhooked some stuff in the course of cleaning the engine bay and can't figure out where one wire should go. To begin with, I can't figure out what the electrical device is that it runs from, as it doesn't appear in the photo in the service manual, nor can I find the combination of wire colors on the wiring diagram.
The wire in question is yellow and looks like it would go to the coil. If so, I don't know which terminal. The
photos show what I'm talking about.

Thanks in advance for any guidance.
Charlie

 

[Ron Kwas]

Charlie;

That is not one of the factory original relay, as shown on the second pic...that looks like the style relay they added when installing AC...I'd trace the wires to confirm. ...I expect you'll find some going to the AC unit under the Dash, and others going to the Mag clutch on the AC compressor. AC wiring was not shown on factory Wiring Diagrams.

Good Hunting

 

[Stiguy04]

I agree with Ron. I got gray hairs trying to resolve my AC wiring. I found some decent guides online and figured it out. If I find the diagrams I’ll post them.

Jason

 

[[email protected]]

Thanks Ron and Jason. I was thinking it might be associated with the a/c. I'll try to dig into that too.

 

[Stiguy04]

Here’s what I had saved on my phone. If your relay has letters or numbers on it I may be able to help by telling you where my connections go. I think my relay has letters instead of numbers.

They’re not that great since I took the picture from my computer screen originally.

Jason

 

[volvogod]

Check out this site to get a lot of 1800 info. It can all be downloaded also.
Click on Documents(Eng)

Volvo 1800 Pictures and global register – A website with all you want to know about Volvo 1800

 

[[email protected]]

Here’s what I had saved on my phone. If your relay has letters or numbers on it I may be able to help by telling you where my connections go. I think my relay has letters instead of numbers.

They’re not that great since I took the picture from my computer screen originally.

Jason View attachment 182069
View attachment 182070

The 1800 pictorial looks like mine, except I have yellow instead of blue. Judging by the terminal end, length, and bends, it looks like my yellow goes to the coil, if that makes any sense. If it does, I guess it would be to the positive post. I'm not too good with electrical stuff.

 

[[email protected]]

Check out this site to get a lot of 1800 info. It can all be downloaded also.
Click on Documents(Eng)

Volvo 1800 Pictures and global register – A website with all you want to know about Volvo 1800

Thanks, lot of a/c info there, but a cursory look didn't show me what I'm looking for. Will dig into it later.

If anyone out there with a '73 ES with a/c is reading this, could you take a pic of this relay, showing where the yellow or blue wire goes, if it can be seen. Thanks!

 

[142 Guy]

The relay is interesting; but, perhaps a red herring. Given that the male spade terminal on the coil appears to be missing a connection (it should be the + terminal), I think that wire might be the switched +12v for the coil. The official 1800 ES wiring diagram shows a brown wire to the coil +; but, on my 142E the OEM wiring harness wire is a big fat yellow one just like in your picture. There should be a similar wire from the coil + terminal to the main fuel injection relay.

If the coil + terminal is missing connections as it appears to be in the photo and if the yellow wire has a female spade connector on it, then I expect it is the switched supply for the coil and EFI relay. As a double check, with the wire loose connect a voltmeter to it to measure the voltage relative to ground. If it measures 0 with the key off and +12v with the key on I suspect it is the switched supply for the coil +.

If the coil + already has two brown wires on it hidden from view, then all bets are off.

 

[Stiguy04]

Charlie,

Does your relay have letters or numbers? If you still need help after 142 guys advise I can trace my relay terminals for you. I replaced my wires so my colors won’t match yours. For me it was figuring out the right terminal to the right item. Pretty sure I have letters. I had to find a breakdown for L, B, S and the mount tab on the fender.


Load=87, 12v out
Battery=30 or 51, 12v in
Switch=86, 12v from switch
Mount=85, ground

Jason

 

[justcharlie]

Are you sure the yellow wire was attached to anything before you disconnected things for cleaning the engine bay?

Have you tried starting the car to see what doesn't work? (Make sure the wire isn't contacting anything.)

 

[Ron Kwas]

Guys;

From Jason's pictures, it is clear that relay is simply an Ign Slave relay, intended to handle the currents of the AC system, so that the Ign Sw doesn't have to...in both 1800 and 122 cases, Red wire brings in power, and Blue wire brings in Ign Pwr to control the relay...Relay should click closed when Ign is powered by key, supplying power to "Evap case"...if wire colors are not consistent with those drawings, just go by the contact position on relay.

Good Hunting!

 

[Stiguy04]

Here’s my 73 ES AC relay. As far as I know dealer installed relay when AC was done. Was my grandmother’s grocery getter she gave me 7 years or so ago. I noted the relay number that corresponds to my letters.

L/87 is going to the AC compressor and a sensor. It’s 1 wire that Ys into 2 at a connection part way down stream.

B/30 or 51 is going directly to my battery with an inline fuse. I put a modern fuse in place.
S/86 is going through the firewall and it is a blue wire.

my ground is the mount tab.

Don’t judge, it’s dirty but she wins classic TSD road rallies so I’m happy.

 

[[email protected]]

Guys;

From Jason's pictures, it is clear that relay is simply an Ign Slave relay, intended to handle the currents of the AC system, so that the Ign Sw doesn't have to...in both 1800 and 122 cases, Red wire brings in power, and Blue wire brings in Ign Pwr to control the relay...Relay should click closed when Ign is powered by key, supplying power to "Evap case"...if wire colors are not consistent with those drawings, just go by the contact position on relay.

Good Hunting!

Since the wire's length, bend pattern, and terminal indicate it would go to the coil, this makes sense. This being the case, I assume it goes to the positive post of same.

 

[[email protected]]

Here’s my 73 ES AC relay. As far as I know dealer installed relay when AC was done. Was my grandmother’s grocery getter she gave me 7 years or so ago. I noted the relay number that corresponds to my letters.

L/87 is going to the AC compressor and a sensor. It’s 1 wire that Ys into 2 at a connection part way down stream.

B/30 or 51 is going directly to my battery with an inline fuse. I put a modern fuse in place.
S/86 is going through the firewall and it is a blue wire.

my ground is the mount tab.

Don’t judge, it’s dirty but she wins classic TSD road rallies so I’m happy.

View attachment 182320
View attachment 182321
View attachment 182322

thanks for the pics Jason. My relay is a bit different, but it is the "S" terminal I am dealing with (yellow wire in pic). Where is that green wire going on yours?

 

[Stiguy04]

thanks for the pics Jason. My relay is a bit different, but it is the "S" terminal I am dealing with (yellow wire in pic). Where is that green wire going on yours? View attachment 182658

The S terminal (blue/green wire) on my A/C relay is going through the firewall to something under the dash. Is one of the red wires going to your battery and the other red wire going to the A/C compressor and/or temp sensor? Assuming the black is going to a ground of some sort. Maybe @Ron Kwas can confirm, if that yellow is your ignition source and "OK" to connect to the coil for that ign source meaning "key on". There's probably multiple ways to wire up the relay with the same results, just depends on how a person wants to go about doing it for ease, wire length, and desired power sources to accomplish the task. Knowing the terminal's purpose and providing the source/destination to them is all you're doing.

FYI - I didn't crawl under my dash, but I suspect my blue wire is coming off an ignition power source in the A/C controls or another ign source under the dash when key is on.

Jason

 

[142 Guy]

I didn't see the connection of the yellow wire to the relay in your first post. With your latest photo and the diagram pictures from the AC instructions provided by Stiguy04, they might have been picking up switched +12v from the ignition coil + terminal. Does the other end of the yellow wire have a female spade connector.

In your last photo, it looks like the top red wire which I think is switched power is resting on the lug for the black wire which is chassis ground. With some vibration, the insulation on the wire is going to wear through and create a dead short to ground. Move the red wire so that it is not touching ground terminal.

 

[[email protected]]

The S terminal (blue/green wire) on my A/C relay is going through the firewall to something under the dash. Is one of the red wires going to your battery and the other red wire going to the A/C compressor and/or temp sensor? Assuming the black is going to a ground of some sort. Maybe @Ron Kwas can confirm, if that yellow is your ignition source and "OK" to connect to the coil for that ign source meaning "key on". There's probably multiple ways to wire up the relay with the same results, just depends on how a person wants to go about doing it for ease, wire length, and desired power sources to accomplish the task. Knowing the terminal's purpose and providing the source/destination to them is all you're doing.

FYI - I didn't crawl under my dash, but I suspect my blue wire is coming off an ignition power source in the A/C controls or another ign source under the dash when key is on.

Jason

One red goes to an ignition-on terminal at fuse box (has in-line fuse) and the other to the a/c unit under the dash. Everything points to the yellow having been connected to the positive post on coil, I guess as the easiest way to get ignition power.

 

[[email protected]]

I didn't see the connection of the yellow wire to the relay in your first post. With your latest photo and the diagram pictures from the AC instructions provided by Stiguy04, they might have been picking up switched +12v from the ignition coil + terminal. Does the other end of the yellow wire have a female spade connector.

In your last photo, it looks like the top red wire which I think is switched power is resting on the lug for the black wire which is chassis ground. With some vibration, the insulation on the wire is going to wear through and create a dead short to ground. Move the red wire so that it is not touching ground terminal.

Got you on keeping the red off the other terminal. Thanks all for your help!