Heater/AC does not work

Hi,

The first thing to happen is this. When the ignition key is turned to the run position, power is provided through the relay to the black wire which is ground. Once that happens, the relay actuates/completes the circuit and power from fuse 30 runs through the resister to the blower motor switch in the vehicle.

Based on the speed selected, the switch provides a ground causing power to run through different resisters changing fan speed.

Remove the relay. There should be two pins that always have power when the key is on. Actually, the connector from the blower motor fuse will have 12v at all times. The trigger power supply will only be with the key in the on position.

If I have to guess, I suspect one of those doesn't have power resulting in power not reaching the resister and switch. Check both of those and let me know what you find.

I attached the wiring schematic below for you to reference. I had to cut the page in half, but I did overlap them. However, the first pic is the one you truly need.

Remember, when you remove the relay, the pins will be numbered. Pins 85 and 86 are the primary side of the relay which causes the relay to actuate. Pins 87 and 30 react to the primary when a switch in the relay is triggered electromagnetically sending power to the system. See pic 3 for pin information and here is a link that better explains how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find.

Take care,

Joe

See pic below.

Hi Joe,
Thank you very much for your reply and the wiring schematic. On the relay that I have, I cannot find any marks or numbers for the pins. I will attach pictures of the relay. On the wiring schematic you sent, I see the relay should be in the engine compartment fuse/relay box, but the relay I have is under the right side of the dash next to the blower motor and the resistor. As you said, I do have +12 Volts at all times on either one of the pins 87 or 30 (I can’t confirm which one since I can’t find marks on the relay or the wire harness), I do have +12 Volts on pin 85 or 86 when the ignition key is turned to the run position I can confirm the third pin (either pin 87 or 30) works properly since when I make a short circuit on them the blower works. For me, there is a problem with the 4th pin wires, because I can't see any reactions when I check for connection to the battery, or to the ground.
I'm not a mechanic, but an electrician. Just when I work in a tiny place and in uncomfortable positions, and when I don’t know what I’m looking for, makes me feel claustrophobic.
It seems to be an issue with the wiring between the relay and the control board, or in the control board itself. Since the control board is the most expensive part of the system, I need a good idea of how to confirm I do not have a problem with the wiring system before I order the control board.
I would appreciate any ideas on how to test all these tiny wires.

Hi,

Okay, it sounds like the secondary is working properly. Also, you have power to the primary when the key is on. Do me a favor. Determine which primary connector supplies. Once you do that, check if there is continuity to round via the last pin.

Also, let me know if you have confirmed the relay is good. I'm not sure why the relay is in a different place. The only thing I can think of is if the vehicle is an early or late production and used the adjacent model year's design.

Take care,

Joe

Hi Joe,

I used extension wires to test the relay. When I connect the power source, from the ignition key to its matching pin and the other pin to its matching wire, the relay does not react at all and does not do anything. Then I disconnected the outgoing pin and measured +12V going through the relay. Last, I connected the outgoing pin to the ground (-) and the relay actuated, I heard a click, and I measured the closed circuit between the other two pins.


Thank you so much for your help.

Hi,

Okay, if I understand correctly, it sounds like you don't have a ground for the primary. Is that correct? If you locate the black wire from the relay, does it have continuity to ground?

If not, in the vehicle, remove the left kick panel. That is where your left foot would lean against when sitting in the driver's seat. There will be black wires there that provide the ground. Confirm it is in good condition. If it appears to be the ground on the secondary, go to the blower motor and check the red wire with a white tracer for continuity to ground. Have the key off and the fan motor switch in the on position.

Let me know.

Take care,

Joe

Hi Joe,

I did check what you asked, but this looks like a dead-end to me. All connections there look good. I don't know which ones to check, there is a lot. Also, at the relay, I don’t have black wires, all wires there are the same color. Please see the pictures for reference.
The main problem in my case is that the on/off switch for the blower does not work, and about half of the functions on the control board do not work too. When I connect the red with the black wires from the last picture, the fan works.

The two wires at the connector are both red and I think they have a black tracer. Is that correct? If so, what did you disconnect the connector from? If that is from the fan motor, one should be green with a yellow tracer.

Also, the first pic appears to be wiring to the PCM. What should I be looking for in that pic?

Let me know.

Joe

I have disconnected the relay from there. This is the way I made the ac/heater work until I find the main issue with it.
I made this picture because I thought you said to look there for ground issues. Unfortunately, I have no idea where all these wires come from or where they go.
Thank you.

Hi,

Okay, I understand. Those wires are from multiple things. What you want to look for are black wires that will be mounted directly on the body sheet metal.

The connector you jumped, where was that originally plugged into? I ask because I'm seeing different colors on the schematic.

Let me know.

Joe