I had a problem starting my MX5 1.8S NB, 1999. It turned over, but didn’t catch. I thought the battery may be a bit low as the car had not been used for approx 10 days - I charged it up no problem, car still wouldn’t start. Bump started it down the hill to the garage, and there it started without any fuss. They did a battery check and it said “replace battery” and they said the alternator was delivering too high a voltage. I have the the back of my mind a vague recollection that MX5 electrics are a bit non-standard. Any thoughts on whether I need a now battery or alternator?
Battery Test results
Midtronics MDX-325P
V1.0
BATTERY TEST
REPLACE BATTERY
Volts 13.03V
Measured 231CCA
Rating 360CCA
Bat. Type REGULAR
Bat. Location IN VEHICLE
STARTER TEST
Volts 10.25V
CHARGING TEST
Volts 15.01V
I have a feeling that setting it to “regular” battery may have been an error.
The 15 volt charging rate will tend to cook the battery. I assume it has been cooked. You could try charging it with a smart chraged but I assume the damage is done.
It would appear you need a new voltage regulator in your alternator before the new battery is installed.
Hi,we use a midtronic machine in out toyota dealership, when they say replace it not always right,had a similar prob with a motor,told the customer to go home and charge the battery, she DIDNT,she bought a NEW one,so i charged the battery and now i own a DECENT operational battery, so tread carefully.
If i was you with a multimeter,you can do some basic checks, like battery voltage, followed by a voltage reading while cranking, i generally use a rule of thumb of no less than 9V reading at cranking then view voltage readings on tickover, followed by a slightly raised RPM then also applying electrical loads to see how and if the voltage fluctuates.
We all do tests differently,no doubt some will say im wrong.
You could try removing your battery terminals and cleaning them, then also follow your earth lead to your chassis and clean this and also inspect and clean if requirred the battery leads to the starter motor and alternator etc etc, dont forget these are views from a techy and i know what am doing.
1 last idea,pop along to a second garage and get a second opinion, hope you get sorted.
Charging voltage of 15V is OK. it is higher than normal due to the AGM battery. CCA is low at 231A I am suprised that this gave 10.25 V at the starter. I presume the starter was under load at the time of test. What should be done is a voltage drop test on the +ve and -ve lines to pinpoint any poor electrical connections also the residual current should be measured, that is the power to supply the alarm, radio memory etc. this shoud be less than 20mA. A quick test is to connect a known good battery across the one in the car, if it cures the problem it is the battery at fault, if not, the problem lies elswhere.
Charging voltage of 15V is OK. it is higher than normal due to the AGM battery.
Jeff,
The original supply battery in the MK2 is the Panansonic, which I believe is an acid flood battery not an Absorbed Glass Mat battery like the newer WestCo battery.
The original panasonic battery is AGM and in my opinion superior to the westco. Hence the charging rate is up to 15V. If you connect a multimeter across the battery terminals and keep the engine speed around 1500 rpm. Read the voltage. shoud be 14 -15V Then switch on headlights main beam, heated rear window, heater blower full speed and rear fog light, this will give the alternator a bit of work to do. The voltage will drop a little but should still be above 13.5V If this is the case then there is nothing wrong with the alternator.
Sorry, forgot the starter test. again multimeter +ve probe on the starter terminal -ve probe to earth. Read the voltage while the starter is being cranked, all other loads being off. Should read over 9.6V As I have said, I personally think this is to low anything less than 10V the starter will not crank the engine fast enough. Bear in mind the MX5 sounds slow to start as there is a reduction gear within the starter motor.
Thanks for your replies chaps. All is well now - I’m glad I didn’t pay out for a new alternator, I had a feeling that wasn’t the problem. I’ve not done a crank test yet (been away) but the car is starting normally now. Will do a crank test and see what I come up with. Cheers. JR