Hi.
I have a Feb. 1982 FJ40 with an OEM Nippondenso AC evaporator and a 12V AC Amplifier.
The PO had undertaken several mods to make the AC system operational and I’m now in the process of getting the system back to its stock configuration. I’ve made several fixes, but am now stuck, and I’m hoping to get some insights from the forum. I’ll first provide some background info that may be useful, and then ask my questions.
Background:
The PO bypassed the amplifier circuitry that controls the idle up, compressor control, and evaporator temp monitoring/control. I’ve attached a wiring diagram of how the PO set up the AC circuit (Fig.1).
In the PO’s configuration, there is no idle up control. In their mod setup, instead of the OEM thermistor, there is a dial rheostat attached to a temp probe; the probe section is inserted into the evaporator tube opening, where the OEM thermistor should go.
The temperature signal is fed to a Bosch relay, and the relay signal is fed to the AC dryer pressure switch, which is then fed to the AC compressor.
I have not pulled the evaporator, but I assume the wiring harness for the evaporator is not installed, nor is the AC main relay. I say that because in the circuit above, the PO rolled all the wiring themselves. As the main relay is missing, the PO spliced in a HOT lead from the fuse box. The evaporator resistor is intact.
In the above setup, the Amplifier ON/OFF switch provides hot to the blower and the above circuit.
I’m now attempting to reset this circuit to that of the below diagram (Fig.2).
Questions:
Disclaimer here: I’m still kinda new to electrical troubleshooting, but I got my Multimeter and am learning as I go!
As in the OEM diagram, my Amplifier harness has 11 connections.
In my truck, the amplifier and main harness connections share most, but not all, of the diagram wire color/stripe configurations. I’ve confirmed continuity to the AC clutch, emissions computer, pressure switch, and pressure switch to VSV (idle-up solenoid). The only diagram connection I cannot confirm is the ground connection (left arrow in Fig.2). On my truck, this unaccounted-for wire corresponds on the harness side and amplifier side, to a blue/red stripe wire (which I find an odd coloring choice, as it appears almost everywhere else on my truck that blue/red wires are hot). Inside my amplifier (Fig. 3), this blue/red (inside the red circle) is fed to the part of the circuit that contains the compressor feed (black/white) and the hot from the pressure switch (blue).
Another data point: I have continuity on the amplifier between the mystery blue/red wire (left arrow in Fig. 2., which per the diagram, is supposed to be the ground wire), VSV, and thermistor (red circles in Fig.2) and a disconnect wire (red arrow in Fig.3) discussed below and not shown in the OEM wiring diagram of Fig.2).
Question 1). What is this blue/red wire for?!
I’ve attached all the components on my truck, and I can get the idle up solenoid to work, but i’m not getting a hot to the compressor. To be extra clear, in all my trials, I’ve never been successful in getting hot to the AC compressor.
Question 2). As I have continuity from amplifier to my emissions computer, thermistor, and AC clutch, and hot from the pressure switch and VSV, I should assume I can’t get the AC clutch to engage because I don’t have a proper ground in my amplifier?
Inside my amplifier in Fig.3, I do have a wire (red arrow) that at least acts like ground at times. This wire connects from the circuit board to the low-speed blower connection (connection occurs inside the amplifier, at the amplifier harness connector). As you can see in Fig. 3., this some-times ground connection has an OEM disconnect.
I actually don’t think that this wire with the disconnect is the ground. I say that because the only way I can get the idle up to engage is if I disconnect the hot (x in Fig. 2) that feeds the blower, which then goes to ground at the blower motor via the PO's home-rolled wiring (as shown in Fig. 1). The ground through the disconnect wire is lost when the blower hot is supplied to the amplifier. So maybe this ground/no ground issue is related to not having the evaporator wiring harness and main AC relay? IDK..at this point I’m very much confused, and any help/insight would be very much appreciated.
Question 3). Is this wire with the disconnect really the only ground? Which then gets me back to Question 1.
Question 4). What is the purpose of making this supposed ground (or whatever this connection feeds) an optional disconnect?
Question 5). At the right arrow in Fig.3, why is hot being supplied twice to the blower? It connects first at this junction directly to the blower, and it then connects through the amplifier blower on/off switch to the L/M/H blower resistor.
Again, I’d be very appreciative of any suggestions insights from the forum. THANKS!
View attachment 1630997
View attachment 1630998
View attachment 1630999
View attachment 1631001
View attachment 1631005
I have a Feb. 1982 FJ40 with an OEM Nippondenso AC evaporator and a 12V AC Amplifier.
The PO had undertaken several mods to make the AC system operational and I’m now in the process of getting the system back to its stock configuration. I’ve made several fixes, but am now stuck, and I’m hoping to get some insights from the forum. I’ll first provide some background info that may be useful, and then ask my questions.
Background:
The PO bypassed the amplifier circuitry that controls the idle up, compressor control, and evaporator temp monitoring/control. I’ve attached a wiring diagram of how the PO set up the AC circuit (Fig.1).
In the PO’s configuration, there is no idle up control. In their mod setup, instead of the OEM thermistor, there is a dial rheostat attached to a temp probe; the probe section is inserted into the evaporator tube opening, where the OEM thermistor should go.
The temperature signal is fed to a Bosch relay, and the relay signal is fed to the AC dryer pressure switch, which is then fed to the AC compressor.
I have not pulled the evaporator, but I assume the wiring harness for the evaporator is not installed, nor is the AC main relay. I say that because in the circuit above, the PO rolled all the wiring themselves. As the main relay is missing, the PO spliced in a HOT lead from the fuse box. The evaporator resistor is intact.
In the above setup, the Amplifier ON/OFF switch provides hot to the blower and the above circuit.
I’m now attempting to reset this circuit to that of the below diagram (Fig.2).
Questions:
Disclaimer here: I’m still kinda new to electrical troubleshooting, but I got my Multimeter and am learning as I go!
As in the OEM diagram, my Amplifier harness has 11 connections.
In my truck, the amplifier and main harness connections share most, but not all, of the diagram wire color/stripe configurations. I’ve confirmed continuity to the AC clutch, emissions computer, pressure switch, and pressure switch to VSV (idle-up solenoid). The only diagram connection I cannot confirm is the ground connection (left arrow in Fig.2). On my truck, this unaccounted-for wire corresponds on the harness side and amplifier side, to a blue/red stripe wire (which I find an odd coloring choice, as it appears almost everywhere else on my truck that blue/red wires are hot). Inside my amplifier (Fig. 3), this blue/red (inside the red circle) is fed to the part of the circuit that contains the compressor feed (black/white) and the hot from the pressure switch (blue).
Another data point: I have continuity on the amplifier between the mystery blue/red wire (left arrow in Fig. 2., which per the diagram, is supposed to be the ground wire), VSV, and thermistor (red circles in Fig.2) and a disconnect wire (red arrow in Fig.3) discussed below and not shown in the OEM wiring diagram of Fig.2).
Question 1). What is this blue/red wire for?!
I’ve attached all the components on my truck, and I can get the idle up solenoid to work, but i’m not getting a hot to the compressor. To be extra clear, in all my trials, I’ve never been successful in getting hot to the AC compressor.
Question 2). As I have continuity from amplifier to my emissions computer, thermistor, and AC clutch, and hot from the pressure switch and VSV, I should assume I can’t get the AC clutch to engage because I don’t have a proper ground in my amplifier?
Inside my amplifier in Fig.3, I do have a wire (red arrow) that at least acts like ground at times. This wire connects from the circuit board to the low-speed blower connection (connection occurs inside the amplifier, at the amplifier harness connector). As you can see in Fig. 3., this some-times ground connection has an OEM disconnect.
I actually don’t think that this wire with the disconnect is the ground. I say that because the only way I can get the idle up to engage is if I disconnect the hot (x in Fig. 2) that feeds the blower, which then goes to ground at the blower motor via the PO's home-rolled wiring (as shown in Fig. 1). The ground through the disconnect wire is lost when the blower hot is supplied to the amplifier. So maybe this ground/no ground issue is related to not having the evaporator wiring harness and main AC relay? IDK..at this point I’m very much confused, and any help/insight would be very much appreciated.
Question 3). Is this wire with the disconnect really the only ground? Which then gets me back to Question 1.
Question 4). What is the purpose of making this supposed ground (or whatever this connection feeds) an optional disconnect?
Question 5). At the right arrow in Fig.3, why is hot being supplied twice to the blower? It connects first at this junction directly to the blower, and it then connects through the amplifier blower on/off switch to the L/M/H blower resistor.
Again, I’d be very appreciative of any suggestions insights from the forum. THANKS!
View attachment 1630997
View attachment 1630998
View attachment 1630999
View attachment 1631001
View attachment 1631005
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