AC install 83

[WestPac720]

On 2/6/2022 at 9:08 AM, WestPac720 said:

So I finally was able to pull the stock thermo switch from evaporator box. Here is how the connect looks. No where in the FSM does the wiring diagram talk about the wire colors going into the the thermo switch. The four pin plug at the end is what was initially connected to where the AC relay would go (assumingly for non AC models).

I am beginning to think that this connection here is the AC relay and thermistor switch combined into one. 

[datzenmike]

Battery power goes to the A/C switch, when ON it passes out the Red/Blue wire to the Thermo switch, which if closed, passes it out on the Red/Yellow wire to the Low Pressure switch, which if closed passes power out the Red/Blue wire to one side of the coil in the A/C relay. The other side of the A/C relay coil goes out on a Red/Green wire to the Fan switch and on any speed other than off, grounds it to energize the A/C relay coil. When the A/C relay coil is energized, the Blue power wire from the fuse box is connected to the Red wire to the Thermal Protector and through it to the compressor and to ground.

 

You say you can hear the relay click when you turn on the A/C switch. Check that you have 12v on the Blue wire at the relay, and with the relay coil energized, you should have 12v on the Red wire to the thermal protector. Less than 12v then the relay contacts are bad OR the F. I. D. C. solenoid is somehow loading the 12v down to 7v. Try disconnecting the FIDC and see if that helps.

 

If you have 12v on the Red wire on the relay then go to the Red wire where it joins the thermal protector. If less than 12v then there is something wrong with the Red wire. If you have 12v then go to the Red wire coming out of the thermal protector and confirm that the 12v is getting through. From here is a Red wire through a connector and to the compressor.

 

 

Kind of convoluted but it's either the relay (even though it clicks) or perhaps the FIDC solenoid is placing a load on the 12v going to the compressor. 

[WestPac720]

14 minutes ago, datzenmike said:

Battery power goes to the A/C switch, when ON it passes out the Red/Blue wire to the Thermo switch, which if closed, passes it out on the Red/Yellow wire to the Low Pressure switch, which if closed passes power out the Red/Blue wire to one side of the coil in the A/C relay. The other side of the A/C relay coil goes out on a Red/Green wire to the Fan switch and on any speed other than off, grounds it to energize the A/C relay coil. When the A/C relay coil is energized, the Blue power wire from the fuse box is connected to the Red wire to the Thermal Protector and through it to the compressor and to ground.

 

You say you can hear the relay click when you turn on the A/C switch. Check that you have 12v on the Blue wire at the relay, and with the relay coil energized, you should have 12v on the Red wire to the thermal protector. Less than 12v then the relay contacts are bad OR the F. I. D. C. solenoid is somehow loading the 12v down to 7v. Try disconnecting the FIDC and see if that helps.

 

If you have 12v on the Red wire on the relay then go to the Red wire where it joins the thermal protector. If less than 12v then there is something wrong with the Red wire. If you have 12v then go to the Red wire coming out of the thermal protector and confirm that the 12v is getting through. From here is a Red wire through a connector and to the compressor.

 

 

Kind of convoluted but it's either the relay (even though it clicks) or perhaps the FIDC solenoid is placing a load on the 12v going to the compressor. 

Sir, thank you for responding. When i get home I will check all these things you've mentioned. Also, just for clarification, the photo that I commented on regarding the non-ac setup plug as seen on the photo posted by madkaw which appears to be the thermo switch and ac relay fused into one unit, was this a factory setup? I'm seeing two types of ac wiring schematics. One (I'm assuming) is with the themo switch and ac relay connected together, and the other with the themo switch and ac relay connected separately. Both styles are affixed on top of the evaporator box as seen from previous photos here. 

[WestPac720]

On 2/6/2022 at 9:08 AM, WestPac720 said:

So I finally was able to pull the stock thermo switch from evaporator box. Here is how the connect looks. No where in the FSM does the wiring diagram talk about the wire colors going into the the thermo switch. The four pin plug at the end is what was initially connected to where the AC relay would go (assumingly for non AC models).

This is the setup i was referring to. It appears that the thermo switch and ac relay wires are fused into the metal housing. I noticed also that the two spade connectors for the thermo switch was connected to the white fusible link. The 86 FSM does not make any mentioned of this type of setup. 

[datzenmike]

I only have the '84 FSM.

 

White fusible link?? I think the White wire is just a wire connected to the Black fusible link.

[WestPac720]

6 minutes ago, datzenmike said:

I only have the '84 FSM.

 

White fusible link?? I think the White wire is just a wire connected to the Black fusible link.

I'm referring to that small white two spaded connector that's shown in the last photo of this post. That small fusible link was just connected to the R/Y wire and R/L wire that comes out of the main harness for the thermo switch.  

[WestPac720]

What are the difference between these two relays? The relay with the wires coming out with the four pin plug is what I removed from my 85 base model which also appears to have the themo switch built in together. The other AC setup just has the AC relay (housing with four pin) and themo switch (not shown) that is connected separately.

[WestPac720]

8 hours ago, datzenmike said:

Battery power goes to the A/C switch, when ON it passes out the Red/Blue wire to the Thermo switch, which if closed, passes it out on the Red/Yellow wire to the Low Pressure switch, which if closed passes power out the Red/Blue wire to one side of the coil in the A/C relay. The other side of the A/C relay coil goes out on a Red/Green wire to the Fan switch and on any speed other than off, grounds it to energize the A/C relay coil. When the A/C relay coil is energized, the Blue power wire from the fuse box is connected to the Red wire to the Thermal Protector and through it to the compressor and to ground.

 

You say you can hear the relay click when you turn on the A/C switch. Check that you have 12v on the Blue wire at the relay, and with the relay coil energized, you should have 12v on the Red wire to the thermal protector. Less than 12v then the relay contacts are bad OR the F. I. D. C. solenoid is somehow loading the 12v down to 7v. Try disconnecting the FIDC and see if that helps.

 

If you have 12v on the Red wire on the relay then go to the Red wire where it joins the thermal protector. If less than 12v then there is something wrong with the Red wire. If you have 12v then go to the Red wire coming out of the thermal protector and confirm that the 12v is getting through. From here is a Red wire through a connector and to the compressor.

 

 

Kind of convoluted but it's either the relay (even though it clicks) or perhaps the FIDC solenoid is placing a load on the 12v going to the compressor. 

I’m still trying to grasp this convoluted process. 

[datzenmike]

9 hours ago, WestPac720 said:

I'm referring to that small white two spaded connector that's shown in the last photo of this post. That small fusible link was just connected to the R/Y wire and R/L wire that comes out of the main harness for the thermo switch.  

 

I don't think it's a fusible link as there is nothing that needs protection that isn't coming through the fuse box fuses. If connected to the R/Y and R/L then it's there to defeat the thermo switch, in effect making it permanently on. This is in series with the relay coil, and as the relay clicks it seems to be working.

[WestPac720]

On 2/8/2022 at 1:14 PM, datzenmike said:

Battery power goes to the A/C switch, when ON it passes out the Red/Blue wire to the Thermo switch, which if closed, passes it out on the Red/Yellow wire to the Low Pressure switch, which if closed passes power out the Red/Blue wire to one side of the coil in the A/C relay. The other side of the A/C relay coil goes out on a Red/Green wire to the Fan switch and on any speed other than off, grounds it to energize the A/C relay coil. When the A/C relay coil is energized, the Blue power wire from the fuse box is connected to the Red wire to the Thermal Protector and through it to the compressor and to ground.

 

You say you can hear the relay click when you turn on the A/C switch. Check that you have 12v on the Blue wire at the relay, and with the relay coil energized, you should have 12v on the Red wire to the thermal protector. Less than 12v then the relay contacts are bad OR the F. I. D. C. solenoid is somehow loading the 12v down to 7v. Try disconnecting the FIDC and see if that helps.

 

If you have 12v on the Red wire on the relay then go to the Red wire where it joins the thermal protector. If less than 12v then there is something wrong with the Red wire. If you have 12v then go to the Red wire coming out of the thermal protector and confirm that the 12v is getting through. From here is a Red wire through a connector and to the compressor.

 

 

Kind of convoluted but it's either the relay (even though it clicks) or perhaps the FIDC solenoid is placing a load on the 12v going to the compressor. 

Mike, does the OEM compressor have the thermo protector built in on top of the compressor itself? I don’t see the connection for the thermo protector separate and apart from the compressor. I only see one butt connector (Black/Red) coming out of the compressor that connects to the only solid Red wire from the main harness.

[datzenmike]

I only have the schematic. Did you unplug the compressor to check the voltage? This would eliminate the compressor (and the thermal protection if it's in there) as a cause of the loading down of the voltage from 12 to 7v.

[WestPac720]

1 minute ago, datzenmike said:

I only have the schematic. Did you unplug the compressor to check the voltage? This would eliminate the compressor (and the thermal protection if it's in there) as a cause of the loading down of the voltage from 12 to 7v.

Yes I did, also after disconnecting the wires to the FICD solenoid, I’m still getting low voltage to the lead wire to the compressor. I’m also suspecting it could also be a ground issue somewhere. Would you happen to know where the location of the ground is for the AC system. The only two grounds I could find are the two that are located on the evaporator housing bracket. See photo that’s attached.

[WestPac720]

Also, Looking at the wiring diagram on the 86 FSM, one of the FICD solenoid wire (Black/green) is connected to a ground wire (black). I’m not sure if this ground wire is near the FICD solenoid in the engine compartment area or inside the cab area.

[datzenmike]

9 minutes ago, WestPac720 said:

Yes I did, also after disconnecting the wires to the FICD solenoid, I’m still getting low voltage to the lead wire to the compressor. I’m also suspecting it could also be a ground issue somewhere. Would you happen to know where the location of the ground is for the AC system. The only two grounds I could find are the two that are located on the evaporator housing bracket. See photo that’s attached.

 

 

12v is read between battery and a ground reference. I would guess that out at the compressor under the hood you used AC compressor case as your ground? If the AC compressor perhaps it isn't grounded properly to the engine through the mounting bolts there will be a loss of voltage. Try using the engine block as ground.

 

3 minutes ago, WestPac720 said:

Also, Looking at the wiring diagram on the 86 FSM, one of the FICD solenoid wire (Black/green) is connected to a ground wire (black). I’m not sure if this ground wire is near the FICD solenoid in the engine compartment area or inside the cab area.

 

If the FIDC is disconnected and the voltage is still at 7, then I wouldn't worry about it being the cause.

[WestPac720]

31 minutes ago, datzenmike said:

 

 

12v is read between battery and a ground reference. I would guess that out at the compressor under the hood you used AC compressor case as your ground? If the AC compressor perhaps it isn't grounded properly to the engine through the mounting bolts there will be a loss of voltage. Try using the engine block as ground.

 

 

If the FIDC is disconnected and the voltage is still at 7, then I wouldn't worry about it being the cause.

The compressor clutch will run with a direct 12v line from the battery leaving me to believe that the compressor is working as it should. The vents also get cold as they should leaving me to believe that the system is charged and not low on refrigerant nor are there any leaks in the system. As for the FICD, I’ll hook that back up. I also checked continuity on all the wires from the fuse box to the, AC switch, thermo switch, relay, resistor, low and high pressure, FICD and compressor and all seem to have no break in the line. I would take this to the shop to have them figure it out but I can guarantee they would simply just add a toggle switch direct from a power source/ fuse box to the compressor and call it a day. I’m the type of person that would rather find the issue and have the system and all the components work the way they should, as if it came out from the factory. I really hate to jimmy rig stuff if I don’t have to. At last, I love my truck and every time I’m challenged with a never ending issue, there is always something that I learned for the day. Your responses have all benefited me in one way or another. I’m sure I will figure this out in due time, I’ll just have to continue to be patient and take advice from you experts. As you once said, there is no stupid question than a question not asked.

[Madkaw]

Are you using the compressor ground while measuring V? 

[datzenmike]

On 2/9/2022 at 6:32 AM, datzenmike said:

 

 

12v is read between battery and a ground reference. I would guess that out at the compressor under the hood you used AC compressor case as your ground? If the AC compressor perhaps it isn't grounded properly to the engine through the mounting bolts there will be a loss of voltage. Try using the engine block as ground.

 

 

If the FIDC is disconnected and the voltage is still at 7, then I wouldn't worry about it being the cause.

 

14 minutes ago, Madkaw said:

Are you using the compressor ground while measuring V? 

 

This is about the only thing left. Just to be safe please check this. If the same 7v then everything else has been eliminated and the relay seems to be the cause.

[WestPac720]

Update: So I checked the ground for the compressor to the block. No issues there. The Compressor is well grounded. So I did a little more digging and decided to jumper the (solid red) and (solid blue) wires on the plug that connects to the “dual” AC relay/thermo switch that I’m assuming came factory compared to your simple AC relay and thermo switch separate setup. You can see what I’m talking about as depicted on the photo concerning the wires I jumped. After jumping the wires, the compressor clutch finally kicked in. Overall, this leaves me to believe that the dual relay/thermo switch configuration is faulty. I’m not sure how to test it to be certain. Lastly, once I connect the AC relay and thermo switch separately I’ll know for sure. 

[WestPac720]

Here is a larger photo of the dual AC relay/thermo switch setup.

[WestPac720]

this piece here is what I’m suspecting is faulty based on my diagnosis.

[WestPac720]

By any chance, Does anybody have the wiring diagram for the AC relay? I want to make sure I can match each pin/wire to the correct pin on the relay. 

[WestPac720]

Update: So i was finally able to figure out the wiring to make everything work as should. I ended up installing the new thermo switch which only has two male spade connectors. The FSM shows the two wires that connect to the thermo switch which are red/yellow and red/blue female spade connectors. To get everything to work,   I ended swapping the red/yellow wire with the solid red wire that connects to the AC relay and which supplies power to the compressor. I connected the red/yellow female spade wire to the AC relay where the solid red was. After doing this swap, everything worked as it should And the compressor kicked ON once I pulled the AC knob out. Once the AC turned on, I waited about 4-5 minutes before the compressor finally kicked off which tells me the thermo switch and the low/high pressure switches are all working as they should. A Couple minutes later the compressor kicked back on. I finally install all the interior pieces dash, cluster etc. forgot to mention the idle was also on point with the compressor turning on and off. After a nice stroll around the block, I measured the center vents temp to read around 45-48 degrees which I’m very satisfied and happy with. Also noting that I since converted the fittings and system to R134a. All the AC components are factory and not aftermarket or swapped from another model. Lastly, thank you to everyone that chimed in and helped out!! Sorry I forgot to take photos as I was just so excited to put everything back together.

[WestPac720]

Here are a couple photos of my interior. During the course of working on the AC and while I had the dash removed, I went ahead and restored all the interior trim/pieces. 

[WestPac720]

Just now, WestPac720 said:

Here are a couple photos of my interior. During the course of working on the AC and while I had the dash removed, I went ahead and restored all the interior trim/pieces. 

No cracks on my dash. Unicorn score. Lol 

[WestPac720]

The truck is not an ST original, rather It is a base model. I’ve since converted everything to match the ST model interior.