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Solving an AC electrical issue on my Hyundai i10

27th September 2024, 16:41 by Rahul Nagaraj

The AC blower would stop intermittently, and gradually remain off for the most part and eventually stopped altogether.

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Introduction

Sometimes, cars throw up never heard of issues, and most likely than not, a systematic problem solving process would eventually lead to a solution. This is a quick account of how such a problem was solved, although the process followed was not necessarily systematic.

"Curriculum" Vitae

The car: A 2011 Hyundai i10 Sportz AT, done just 42,000km and in absolutely top shape

The driver : A lady surgeon for whom this car has to offer a reliable home to hospital(s) commute, since most of her professional life revolves around emergencies

The problem

The car was doing its duty dutifully all along, but a few days ago, the AC blower would stop intermittently, and gradually remain off for the most part and eventually stopped altogether. Feedback received was:

1. Blower was not turning on at any of the 4 speed settings
2. AC compressor switch when pressed wasn't turning on

It was as if there was no power to the AC module. Typical issue one would notice in the aircon was the compressor clutch failing to engage, and that would most likely be due to a weak compressor clutch electromagnet, but this one was strange. I had some time on hand off work, so decided to get down to see if I could solve this.

Initial solutioning

The common formula of checking for blown fuses, and power supply to the circuit

Constraints faced

1. Owner manual not available; so getting to know the relays in the BCM was a task
2. Failing light - the car was to come at 3pm but eventually came at 6pm
3. Inside fuse cover did not say anything about the relays; it only talked about the fuses
4. (Expecting too much from an owner) - service manual n/a

The process of finding out the culprit

1. First checked the Aircon Switch fuse, the Aircon Compressor fuse, Aircon Compressor relay, Aircon blower relay, the Aircon Blower fuse. The fuses were all fine (checked for continuity using a multimeter), the relays looked fine too and showed NO signs of wearing. In fact, the relay internals were fine too
2. On the inside of the car, checked for any fuses related to the Aircon switch and found none
3. Noticed that one brown relay (35A) on the inside was rather hot compared to all other relays in both the fuse boxes. Since this was an unknown relay, and led me to suspect it due to its high temperature, I put the "apparently good" 35A relay of the AC blower in its place but the Aircon still did not turn on.
4. Another relay was swapped and put into the Aircon blower relay slot but still did not work
4. This was like hitting a dead end, but I do not generally give up. For trial, I swapped the Aircon blower relay with yet another 20A relay, and bingo, the aircon started working. The good looking 35A relay, which showed no signs of wear or sparking, or pitted points inside had actually failed.

Happy that the problem was solved, I asked for another relay from a store closeby and decided to put this new relay into the slot for the Aircon blower, while shifting the OE relay back to its original slot for the Radiator Fan. All's well that ends well, or that's what I thought. I packed up my few tools and was ready to leave when I discovered that the power windows were now not working. Oh God!

Back to diagnosis

With no manual in hand, I was shooting in the dark (it was 7:30pm and dark already). I chanced on a video that actually showed all the fuses and relays on the i10. Only then I realised that the brown relay on the inside was the Power Window relay. Then it dawned on me - the "hot" relay might actually have been the good one while the normal temperature 35A one removed from the Aircon blower slot and slotted into the Power window was indeed the culprit - and sure enough, as soon as the "hot" relay was put in, the windows started working.

Again, time to rejoice, but not yet!!

The fuses inside the car