82 FJ40 AC Amplifier Issues

Discussion in '40- & 55-Series Tech' started by Eric Kolb, Feb 11, 2018.

  1. Eric Kolb

    Eric Kolb

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    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).

    [​IMG]

    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).

    [​IMG]

    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).

    [​IMG]

    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

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    Last edited: Feb 11, 2018
  2. cruiserbrett

    cruiserbrett Moderator

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    I can’t answer all your questions yet, but as I recall:

    12v is supplied to the blower motor. The switch in the amplifier chooses which ground path to use(through various stages of resistor, or in the case of hi, a direct ground)

    The bullet connection inside the amplifier splits the fan switch and the clutch control portions of the board.

    The ground to the amplifier is intact as you determined, intermittently. Only grounded when the fan switch is in a H NL position, not grounded in OFF.
     
  3. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    You say the amp hasn't spit out 12V for the compressor clutch. IME, it will only output 12V when all the logic conditions are met: Engine running above ~600RPM, pressure switch continuity, thermistor above ~35*F...and the kicker: all other components plugged in and operable. For example, if the idle-up VSV is not connected, the magic box will not energize the clutch.
     
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  4. Eric Kolb

    Eric Kolb

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    Thanks Brett and Jim for your responses!

    Brett: I'm glad to know that the switching ground is actually part of the design. The issue I'm having with the it, is that if I have 12V supplied to the Amp via "X" in Fig. 2., the ground on the Amplifier circuit-side via the bullet, *looses* ground when I switch the fan on. If I don't supply 12V via X, the VSV indeed switches ON when I switch the fan ON.

    I'm wondering if the circuit logic is determining that my mystery blue/red wire is not operating correctly (i'm assuming the blue/red is not connected correctly, or to whatever it's supposed to be)?

    Jim: Yes, all the components you mention are meeting the supposed requirements per the wiring diagram. I will mention that the only components that my truck are missing are those associated with the air pump. Per the wiring diagram, there's no talking of the air pump solenoids with the AC Amp.....maybe I'm wrong there?

    The wiring diagram shows two grounds through the Amp: one through the blower, and a dedicated ground line out. I can get the ground through the blower, albeit by only removing the 12V into the Amp, but it still appears that I don't have the other dedicated ground out :(

    I previously attempted to ground the blue/red, and I ended up blowing the circuit fuse.

    Can anyone else on the board chime in abt this blue/red wire that may or may not be a ground?

    Thanks again, guys!
     
  5. Eric Kolb

    Eric Kolb

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    Thanks Brett and Jim for your responses!

    Brett: I'm glad to know that the switching ground is actually part of the design. The issue I'm having with the it, is that if I have 12V supplied to the Amp via "X" in Fig. 2., the ground on the Amplifier circuit-side via the bullet, *looses* ground when I switch the fan on. If I don't supply 12V via X, the VSV indeed switches ON when I switch the fan ON.

    I'm wondering if the circuit logic is determining that my mystery blue/red wire is not operating correctly (i'm assuming the blue/red is not connected correctly, or to whatever it's supposed to be)?

    Jim: Yes, all the components you mention are meeting the supposed requirements per the wiring diagram. I will mention that the only components that my truck are missing are those associated with the air pump. Per the wiring diagram, there's no talking of the air pump solenoids with the AC Amp.....maybe I'm wrong there?

    The wiring diagram shows two grounds through the Amp: one through the blower, and a dedicated ground line out. I can get the ground through the blower, albeit by only removing the 12V into the Amp, but it still appears that I don't have the other dedicated ground out :(

    I previously attempted to ground the blue/red, and I ended up blowing the circuit fuse.

    Can anyone else on the board chime in abt this blue/red wire that may or may not be a ground?

    Thanks again, guys!
     
  6. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    You're right, there is no connection between AC amp and other systems, like emission controls. But everything for the AC amp has to be connected & within spec.

    Random thought: Is the tach input wire connected from coil tach lead to ignitor?
     
  7. cruiserbrett

    cruiserbrett Moderator

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    There is a decent discussion with a BJ/HJ a/c factory wiring diagram buried in this section somewhere.

    It’s missing the coil connection as it’s for diesel but pretty complete aside from that.

    Based on re-reading the first post you need to establish whether the factory wiring is present along with the main relay. It’s not going to work without all the factory Wiring connected as designed. The amplifier is not easily fooled...

    What’s more concerning is whether the amplifier would work even if it was connected to everything properly. After all, someone went to a lot of work to bypass it for some reason..
     
  8. Eric Kolb

    Eric Kolb

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    Thanks Brett and Jim.
    RE: coil question. Yeah, I do not have continuity from the the coil negative; I was at first suspicious of this, but in my checking further along the circuit, I do have continuity from the distributor to the main harness side of the amp, so I've been assuming that the igniter circuitry is such that it is the reason continuity cannot be measured at the coil negative. Do you believe continuity to the distributor is sufficient confirmation that a timing signal is getting to the AC amp and emissions computer? I'll say that all of the installed associated emissions stuff is working correctly.

    Brett: yeah, I've been wondering what is the true reason why the PO went through such a bypass. The truck was kind of a basket case when I purchased it; the carb did not have the idle up circuit, and the manifold was missing the proper vacuum connections for the idle up solenoid, and the VSV solenoid was not present. In fact, all of the vacuum system was jacked up; missing or crossed connections, etc. The PO had the AC compressor located where the air pump is supposed to be, and the compressor was not a Nippondenso. Furthermore, he had a single-belt main pulley configured to run all of the accessories :( Of course, it was sold through consignment (i've come to realize the PO runs a fj40 puppy mill), and the agreement was that he wanted no contact with the buyer.

    So....from the build he did, I can see his work ethic is lacking and so I've been working under the assumption that his home-rolled amp job is a reflection of his inability to FINISH THE JOB. I'm actually hoping that's the case, cuz that then means it should be largely straightforward to fix the issues. To be clear, I installed a 3-belt main pulley, installed a new nippondenso compressor in the correct location, fixed all the vacuum issues, etc.

    I've looked high and low for a factory AC harness, without any luck to show for it. That has kept me from attempting to acquire a relay, although it appears that OEM AC main relays are still possible to come by. I'll go ahead a purchase one.

    To the boards: does anyone have a factory AC wiring harness (or main relay)?!! I'll gladly purchase either.

    I'm thinking of taking the amp to a shop for testing of the circuits, to make sure everything at least looks good from the circuit component side.

    And I've dug quite a bit through the forums, but I don't think I've come across the discussion abt BJ/HJ a/c factory wiring diagram. I'll look again.

    Thanks again!!
     
  9. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    Get an AC subharness from a rusted FJ60?
    Wires won't be right length, but will have correct color codes, connectors & continuity.
     
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  10. cruiserbrett

    cruiserbrett Moderator

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    I don’t think the evap harness is similar between fj40 and Fj60.

    Luckily the relay is simple. Any 80’s Toyota heater relay is the same.
     
  11. Eric Kolb

    Eric Kolb

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    Thanks for the leads! I'll start investitgating loom capatibility, and it sounds like the relay sourcing will be easier than I thought.

    I've spent the free cycles of the last day developing a plan for how to systematically narrow down blue/red connection candidates.

    Damn frustrating....
     
  12. cruiserbrett

    cruiserbrett Moderator

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  13. cruiserbrett

    cruiserbrett Moderator

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    Additionally, the FJ55 a/c wiring is different so don’t kill yourself looking for the FJ55 OEM a/c manual.

    Also, I have the oem fsm for the a/c amplifier and it’s all theory. Don’t worry about it. It will not help, for two reasons. It’s all theory and no actual hard circuit diagram for the FJ40 amplifier, and it’s for the early-mid 70s amplifiers.
     
  14. Eric Kolb

    Eric Kolb

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    Thanks for the info and the link! I'm reading it now.
     
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