AC Fan not blowing

[caliport]

Model: 1999 i30
Problem: Fan not blowing
Already Tried: Replacing Amplifier
Status: Fuses OK, connectors are tight

From reading the searches, it seems that replacing the 27761-70T03 Amplifier works miracles, but am looking for pointers on another cause for instantaneous fan failure.

On the assumption that it was the Amplifier I spent $150 on a replacement from the local dealer and replaced mine. No change. Ran the tests suggested in the how-to-fix-your-fan-control-amplifier-t433421.html thread and both test the same on thermal cutout and G/35 transistor.

Most blower failures are preceded by symptoms, but there were none, so am not inclined to blame the motor yet.

Any other suggestions gratefully received.

[loystock]

We need model year of your I30.

It's not a good idea to replace a component without doing preliminary fault isolation. It can be expensive. You may just have a blown fuse, lose connection, problem with the harness, etc. Also there is a built-in diagnostic for you I30, from the oldest 96 model to 01.

[caliport]

> We need model year of your I30.

Corrected

> It's not a good idea to replace a component without doing preliminary fault isolation. It can be expensive.

Did the obvious, checked fuses (blower(2) and AC), wiggled connectors after removing the glovebox. Lumped those in with 'no symptoms' (edited original post to spell them out).

> Also there is a built-in diagnostic for you I30, from the oldest 96 model to 01.

The only reference in the diagnostic to the blower motor is the nominal voltage in the HA-32/HA-36 tables. None of the tests seem relevant to a non-operational blower.

The lack of warning and instantaneous nature of the failure suggests an immediate cause like loss of power and that points to fuse or amplifier. That's what has me puzzled, both of those are okay.

[loystock]

You should have been clear as to what you have done before so we could have gone straight into troubleshooting. Having worked in electrical/electronic circuits for a long time, anything can go wrong, sometimes w/o a warning.

I'm assuming you have a copy of the FSM since you have referred several pages into it. Go to page HA-68&69 for the diagnostics of the Blower Motor. Cross-reference that with the Schematic Diagram on page HA-55 and the Wiring Diagram on page HA-58.

Essentially, the Blower Motor receives 12 VDC (higher, depending on the battery condition and if the alternator is running). The Fan Control Amplifier (FCA), a.k.a. Resistor, controls the actual voltage across the Blower Motor,@ 0 VDC with Blower OFF; 5-12 VDC with blower ON. The FCA is essentially a power transistor (FET) which receives power (Source-Pin 1) and bias voltage (Gate-Pin 2) from the AC Auto Amp. So depending on the blower status/speed selection, the potential on Pin 1 of the FCA is from 0-12 VDC. The Bias Voltage (Gate, Pin 2) is controlled by the AC Auto Amp as a function of the Blower status/speed selection (2.5 VDC more or less). Pin 3 of the FCA goes to chassis ground. The higher the blower speed selected, the higher is the bias voltage, resulting in better conductivity for the FET (lower resistance). So if the FET is 'ON,' the voltage at Pin 1 of the FCA (Pin 2 of Blower) goes down to as low a 0 VDC at full blower speed (corresponding to @ 12 VDC potential across blower motor).

If you understood the description above, can follow the wiring diagram and has a multimeter (DVM), then you can follow the diagnostic procedure on page HA-68&69.

So the problem could be with the blower, harness, ground connection, fuses, FCA, AC Auto Amp, etc. Since you have done preliminary checks, we'll focus on the availability of power, control signal and return line (ground) to the blower.
1. Ignition ON: Disconnect blower connector and check voltage with respect to chassis ground - 12 VDC or higher. If not, problem is on the supply side (fuse or wiring). Repair/replace as required
2. Ignition OFF: Check continuity between connectors of Blower Pin 2 and FCA Pin 1 (Source) - resistance must be @ 0 ohm. Repair as required
3. Ignition OFF: Check continuity between FCA connector Pin 3 and chassis ground (any metal ground point in the car) - resistance must be @ 0 ohm. Repair as required.
4. Ignition OFF: Check blower motor coil resistance on Pins 1 & 2 of the receptacle (I don't have the spec for the blower motor resistance) - an open (infinite resistance) or short (0 resistance) indicates a bad blower.
5. If resistance across blower motor coil is valid, apply 12 VDC (+ on Pin 1 and - on Pin 2) to the blower and see if the blower runs at full speed. You may have to use long jumper wires to do this. If the blower runs, problem is somewhere else - connector/harness to/from AC Auto Amp, harness to/from FCA, or the AC Auto Amp itself.

[caliport]

Thanks for the detailed list of actions, it is an excellent tutorial on what to do.

> Go to page HA-68&69 for the diagnostics of the Blower Motor. Cross-reference that
> with the Schematic Diagram on page HA-55 and the Wiring Diagram on page HA-58.

Unfortunately, the schematics are incomplete.

Procedure 8 says to "Check power supply circuit and 15A fuses #2 and #3 located in the fuse block." That just felt 'wrong', every car I've ever had used a relay for the blower.

There are three relays next to the fuse box under the steering but they are a big secret. Howcum?

- Fuses under the hood are identified
- Relays under the hood are identified
- Fuses under the dash are identified
- Relays under the dash are NOT identified

The relays are 25A 25230-79981s, so identified them as A, B, C from the top and rotated their postion. When the ignition was turned on, the AC Auto Amp was dark, so switched them back and it was lit. When relay C was replaced the blower started.

The cabin relays are:
- Top: Unidentified
- Center: AC Auto Amp
- Bottom: Blower

[loystock]

I'm glad you used your experience to approach the blower motor problem. Yes, there is a mistake in the wiring diagram (HA-58) as it does not show the Blower Motor Relay downstream of Fuses #2 & 3. The relays are actually identified in the Electrical System chapter. Go to page EL-7 (Power Supply Routing Schematic Diagram) and EL-361 (Location of Electrical Components, Passenger Compartment). The three relays are clearly identified as follows:
Top: Accessory Relay
Center: Ignition Relay (which controls power to the AC Auto Amp, aside from other circuits)
Bottom: Blower Motor Relay

[caliport]

A troubleshooting sequence of fuse, relay, amplifier would have knocked this problem off in <10 minutes with nothing more than a screwdriver for a tool.

I shudder to think how much this would have cost had my wife taken it into the dealer like she wanted.

I am surprised that this failure mode has never been noted anywhere else, surely I am not the first owner to have had a relay fail. At least this thread now exists to potentially help another puzzled owner.

[loystock]

You are right about the relay. However, from what I've seen in this forum, most of the blower problems are associated with the fuses, blower itself, the harness and the FCA. And yes, I wish the HA wiring could have been better to reflect the presence of the relay instead of having to cross-reference with the EL chapter.