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Story of Punto's sudden battery death

Discussion in 'Engine Compartment' started by RaviHegde, Apr 7, 2014.

  1. RaviHegde

    RaviHegde Regolare

    Messages:
    299
    Karnataka
    14.62°N 74.85°E
    Grande Punto 1.4
    I "was" a happy owner of Fiat Punto 1.4 E+ for last 4+ years. I am saying "was" because right now I am not very happy about the situation. I had gone on a 500 km trip late last week. Car had behaved very well during the trip. I came back home and parked the car. Next morning went to the garage and pressed the remote button - no response. My extended warranty ended at the end of 50 months last month and this is the state of the car. Does Fiat embed some time bomb in their cars so that they die just after the extended warranty ends? To see what happened I opened the driver side door using the key and switched the ignition to MAR position. Dashboard did not show any signs of life. I suspected battery is dead. Pulled out the multi meter and checked battery voltage. It showed dismal reading in the vicinity of 10 V indicating dead battery. Some problem killed less than 1 year old battery which was in very good condition 15 hours back! What can it be? I never leave any lights on when I get out of the car. Therefore it was not my oversight that killed the battery. I could not suspect the alternator because battery was in very good condition indicated by Amaron battery's status indicator when I had checked the battery before the trip. Only other thing I can think of is the AC relay. I remember having read this story in some threads in this forum. I decided to try some diagnostics with the AC relay problem assumption.

    However, there was no way for me to test anything with a dead battery. Battery shops won't help because all battery shops in my area are closed on Sundays. There came my Sukam inverter for rescue :) Pulled the battery out of the car and connected it to the inverter for charging it. It took several hours to show "battery full" indicator. Put the battery back into the car for starting the diagnosis. Connecting the battery to the car immediately confirmed the suspect is the culprit. I heard the characteristic "tak" sound of the AC clutch engaging as soon as I connected the battery negative terminal. Heard another "tak" sound when I disconnected the battery. I also observed the AC clutch plate (shown by the arrow) moving when the AC relay engages/disengages the AC clutch.

    AC-clutch.jpg

    Final confirmation is testing by pulling out the AC relay. Unfortunately owner's manual does not indicate the position of the AC relay. I had to use some threads in this forum to identify the AC relay. See the picture below. I have painted red box around the AC relay. Pulled out the AC relay. Connecting the battery negative terminal now DID NOT make any "tak" sound. AC clutch plate is not moving. Yaahoooo ... I congratulated myself for the quick diagnosis and a temporary resolution of disconnecting the AC relay.

    fiat-1.jpg

    That is one major design mistake by Fiat. Why should the AC system come to life when the ignition is switched off? Why Fiat does not ensure all such "battery eating parasites" are completely disabled when the ignition is off?


    I wanted to see what is wrong with the relay. I opened the disconnected relay to investigate why the relay is behaving like this. This is a SPST relay rated at 20 A with 100 ohms relay solenoid resistance with a 560 ohms resistor soldered in parallel to the solenoid coil. 560 ohms parallel resistor is to dampen the back EMF I believe. A better job of dampening back EMF can be done by a diode though. I think cost cutting lead to using a resistor instead of a diode.

    relay.jpg

    Leads X and Y are the leads for energising/activating the relay. Leads A and B are the relay switch leads. I checked continuity between the leads A and B of the relay. Multimeter sounded "beeeeeeep" indicating the leads are connected. That is tne next major mistake by Fiat - wrong relay design. Why (and how) on the earth will a relay turn on when it is not energised? Close inspection showed this relay has very short throw of 1 mm (or may be less). With such a short throw and high current like 20 A there is always a danger of short circuit. Flimsy relay design did not help either. I suspect the relay connection leaf being so thin and not having good spring action bends the leaf into a permanently connected position. Indeed that was the problem because I could get the relay back in working condition by slightly bending the leaf back to straight position. I plugged in the relay in the fuse box and tested it. AC worked perfectly. When testing the relay I observed that the relay heats up too much even with 5 minutes of AC usage. That is one more problem because the connection leaf gets "fatigued" because of continuous heating when it is in use. That is also a reason why the leaf does not get back to its original position and remains in connected position after long use. This relay design is bad, very bad.


    If I buy a new Fiat replacement relay that is also going to be of equally bad (or worse) quality. I don't want to always live in the fear of this relay killing my battery without any warning. Instead I am thinking of using a good quality automotive relay of more than 20 A contact rating with 100 ohms solenoid resistance (with 560 ohms resistor in parallel to solenoid to keep the electricals happy) like Shopping.kitsnspares.com. Please suggest if you know of any other better alternatives. If I go with my thought of substituting non-Fiat relay I may face challenges in the pin configuration department. I will have to do some tinkering with the connectors or solder on wires from new relay to to the old relay connection posts to use the new relay. Hope that project will go through smoothly. Will post the results when I do that. Until the replacement relay arrives, I will have to enjoy the car ride without AC in coastal Karnataka summer :-(
    21 people like this.
  2. PaddleShifter

    PaddleShifter Staff Member Janitor

    Messages:
    2,697
    Chandigarh
    Grande Punto 1.3
    Very informative thread first of all. I am not aware of any other alternatives so would not be able to contribute anything here.
  3. aashish_19

    aashish_19 Amatore

    Messages:
    198
    Noida
    Grande Punto 1.2
    Bravo!!!!

    Brilliant explanation...in the start I was very much in enthu to read it...but so much electronic concept came in between n I was like :-()

    Then I prefer to read in hurry to finish and read the conclusion part.... Imho ....it was too good catch but not sure if this is the real reason as mine having oem exide battery 2.5 yrs old and still it is going on ...

    Its was just my novice opinion and it can be ignore to some extent :)


    Sent from my RM-846_im_india_233 using Tapatalk
  4. asimpleson

    asimpleson Esperto

    Messages:
    3,000
    Heptanesia
    Linea 1.3
    Excellent job, Rajiv Hegde. :up

    This is such an old problem even with the Siena. This is precisely word to word what I have faced not once, but many times in my Siena D. I am shocked they could not workout around this relay issue. I always wonder why cannot these people use relays that can be found in regular places where other manufacturers used regular ones, that can be found in most automotive stores. These relays are even expensive compared to the competition. For me this issue was solved buy some ex-Fiat SC electrician after hours of trying to figure out the relay failure and possible issues causing this failure.

    To my knowledge and experience no aftermarket relay worked in lieu of the one provided by Fiat, also maybe because of specification mismatch blunders of half baked car electricians I had to deal with.

    Kind request to use your own expert judgement to find a suitable aftermarket replacement. I will be happy if you do find a good example and brand. You seem to have caught the problem, but my hunch is that you may need to dig deeper because there maybe some other underlying or inconspicuous issues here. I have tried to seek explaination for this issue but was never able to reach it's roots. Or you maybe correct about the bad choice of relay or design. Please post as you progress.

    Thanks again for the detailed post.
  5. Iyu

    Iyu Timido

    Messages:
    14
    bangalore
    Will manually switching off the AC, negitate the issue of AC relay failure
  6. asimpleson

    asimpleson Esperto

    Messages:
    3,000
    Heptanesia
    Linea 1.3
    Just realised from the link in your post. The Panasonic type has different terminal or pin layout I guess. Will it work plug and play. Or you plan to modify wiring?

    - - - Merged Post - - -

    :confused: I dont think that is the problem here. A faulty relay switch will activate wrongly anytime unless bypassed or superseded or fail-safed by a bigger manual kill switch, like by the car ignition key for example. Relay failure is one part. Stopping a failed relay to activate and draw current from a car battery in idle is another issue. This is why the battery died due to relay malfunction.
    Last edited: Apr 8, 2014
  7. RaviHegde

    RaviHegde Regolare

    Messages:
    299
    Karnataka
    14.62°N 74.85°E
    Grande Punto 1.4
    You are right. I did not find any after market relay matching the terminal layout of stock relay. I have some idea to make it work. I will have to exploit the empty space inside the fuse box + some soldering skills to make it work Will post the details when I try it.
  8. ghodlur

    ghodlur Esperto

    Messages:
    2,326
    Thane
    @Rajiv

    Brilliant explanation and diagnosis. I would suggest write to Fiat India asking them for an explanation for using substandard parts in their cars.

    I was surprised to see a wrong Relay being used in a car. But using the Inverter battery to charge the car battery was clever thinking on your part.

    Do update the replacement relay you bought.
  9. naruf1

    naruf1 Amatore

    Messages:
    170
    Namma Bengaluru
    Great Insights and diagnosis, however, is this engaging of AC clutch when battery connected applicable for Dynamic/Active variant as well or only for Emotion (With ACC)? Need to check on my ride. Nevertheless, the diode should have been used as suggested.
    Last edited: Apr 8, 2014
  10. RaviHegde

    RaviHegde Regolare

    Messages:
    299
    Karnataka
    14.62°N 74.85°E
    Grande Punto 1.4
    It will help to avoid battery drain when the manual override is turned off. But, it will cause problems with climate control in case of models with climate control and AC cooling settings in models without climate control. Temperature control thermostat (climate control or non-climate control both) uses the same relay to engage the compressor when the cabin temperature is more than the set temperature. It disengages the AC compressor when the temperature starts going below the set temperature. It engages the compressor when the temperature starts rising. This controlled turning on and off of the compressor is the key to maintain the set temperature inside the cabin. This mechanism totally fails when the relay is permanently connected like this. For getting the same effect the driver has to manually keep switching on and off the manual override. Instead of automatic climate control, it becomes driver assisted climate control or the driver becomes the thermostat :)
    Last edited: Apr 8, 2014
    1 person likes this.

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