last week i noticed on my mk1 1.8 classic that the turnover was sounding weak, sounded like a classic flat battery.
i bought a new battery on the same day, a bosch silver line, which seemed a little flat too so i charged it for 12 hours and after that time it started very strongly.
next day i started it again and the same flat sounding start again, and i mean only just start, very weak, basicly back to square one. i have charged it again a few times and it starts after charge very well, then go to the garage for fuel 5 mins away and it only just starts back up, sounds like a very flat battery again.
Hi, it sounds like the alternator isn’t charging the battery. Have it checked by an auto electrician, or if you have a volt meter, check the battery for 12.6V = fully charged. Then start the car and check for around 13.5V at 2000 rpm.
no its not an auto; we also thought the alt wasnt charging it but if you start from a full charge run it for 5 mins and try to restart its the same flat sound on turnover again so it hasnt really used any battery; also when not turned on and with the ignition turned on, i can run the radio, fan on full speed, mainbeams on ect and everything very strong indicating a strong battery,
Hi Steve, so either the starter itself or more likely;
a poor engine to chassis earth connection
a poor battery neg ground connection
a poor pos power connection on the starter motor itself
That is; check all the heavy battery and starter and ground strap connections. What can happen is a connection goes poor/high resistance. It will work fine for all normal functions as they only draw 10A - 20A so the voltage lost across it is not great (Ohms Law). The starter motor though will draw 100A+ under load. Even a small resistance at that current causes a large voltage drop so the starter turns slowly and the voltage isn’t there for a good spark, giving exactly the same symptoms as a flat battery.
thx rich, took your advice, cleaned all the conections on earths, including all contacts on battery and engine to body earth, its still the same, only one not checked is the one on the starter as its so hard to get to without ramps. no clicking from starter, it sounds almost dead at first then a second or two later sounds a little stronger then starts!!
Hi Steve, well worth doing anyway whatever the outcome, but sod’s law it may well be that one which is either loose or corroded.
You need to get at that starter connection next, to either clean the connection or remove the starter.
There were different starters depending on year (what’s yours?) but the circuit was similar and here’s one for 1994 in which you can see that the battery pos goes directly to the starter terminal. It is a heavy connection and must make a good connection with the starter so remove and scrape it clean.
Be careful to disconnect the battery before going near that terminal as if the pos lead touches the chassis (or your tools bridge it etc) there is no fuse protection…
got a friend over lastnight from local mazda garage, tested things that i could’nt do.
not an earth fault or ignition fault but a new starter motor required.
batterys putting volts into the starter too.
it seems very intermitant, he says it depends which seg it falls on in the starter as some maybe dirty. looks like a pig of a job to get too plus the price of starters seems quite high.
Hi Steve, Ouch, could just be the brushes but either way it’s got to come out and then you’d have to find the correct brushes and hope the commutator and all windings are ok.
