g40jon
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Posts: 2,569
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Oct 14, 2016 22:26:42 GMT
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Tonight I decided to take the mx for a quick spin. All started off fine, got 4 or 5 miles down the road and the radio started playing up, cutting in and out. Didn't notice any other issues. So after 10-15 mins of getting miffed with the radio doing odd things I decided to pull into a lay-by to see what was up with it. My amp is in the boot, so I switch the engine off to open said boot. Checked the amp wiring, all looked good. Turned the amp gain down a touch, then got into the car ready to drive off.
Turned the key and click,click, click went the starter solenoid. So I figured the battery had gone flat due to alternator failure. Messaged a mate to come out with some tools. He turns up with a multi-meter, so we measure the battery voltage. Just over 13 volts, odd! So I decide to try starting it and blow me the car starts. We then stick the meter on the battery again and measure close on 15v! This dropped once the electrical system was loaded up, i.e. lights on, heater on, stereo on, now showing around 13v.
We decided to chance driving it back, so I turned off all electrical items bar the headlights, we managed it just, however the lights were about 3 candle power by the time I got on my drive. I then turned the lights off, measured the volts, now showing close on 15v again! Turn the lights on and they are again normal brightness.
Our thoughts are a goosed voltage reg, however we both noticed a burning rubber kind of smell, which got me wondering if a slack belt could cause the fluctuation in charging? Any ideas or suggestions?
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Oct 14, 2016 23:13:46 GMT
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Hi, I would say that's a bad connection on where the car picks its power up or from an earth. Sometimes the power is pick up from the power lead on the starter and if it has a rubber boot on it that has been getting hot enough to smoke. Or there's bad earth connection and it's earthing through another route, maybe the handbrake cable and the plastic covering has got hot. So just a case initially of going round all the power and earth connections and checking they're all clean and secure.
Colin
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Oct 14, 2016 23:18:44 GMT
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A slack or damaged belt could cause it.If it has a chunk out of it or something it can slip and give a burning smell and obviously erratic/no charging.
Voltage reg is certainly possible but it wouldn't smell i wouldn't have thought.
If it's a MK1 the regulator is in the alternator and can be replaced on it's own.
On the MK2 it is part of the ECU and they go sometimes with water ingress.
Certainly check connections and earths too.I had a minor panic the other day in mine when the oil pressure gauge suddenly dropped like a stone and was fluctuating all over the place,turned out to be a bad connection on the sender.
Was the belt making any noise,squealing etc and was the battery light on?
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g40jon
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Posts: 2,569
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Oct 14, 2016 23:56:36 GMT
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The belt hadn't been squeeling, however it has done on really wet days and I did have an issue with the tensioner going slack a year or so ago. The car has nearly 200k on it, so it could well be a worn alternator.
The battery charge light didn't come on when the problem first appeared. It did start to flicker just as I pulled into my cul-de-sac, but by this point the battery was pretty drained. Battery wasn't hot, alt connections appeared secure and also weren't hot.
The car also has some added earth straps between the chassis and engine which I added for good measure back when I first bought the car 5 or 6 years back.
I also run relayed headlights via a home-made loom. I first noticed that the radio was cutting out when going onto high beam.
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Alternator brushes could be a culprit but again i wouldn't expect a burning rubber smell like that.
I think i'd be looking at the belt first,if it's gone shiny or has got oil on it it might be slipping under heavy load.They can get hot and slip with no squeal.Was the belt or alternator pulley hot?
Ticking over on the drive without heater,radio on etc it's maybe just marginal enough to show 14 plus volts at the battery.
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g40jon
Posted a lot
Posts: 2,569
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Yeah my experience of alternator failure (and having owned many high mile cars, I have had a few experiences)I would have expected the battery light to flicker at some point if the brushes were failing..
The belt was warm, but not hot. It was a bit difficult to investigate further due to the lack of light
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g40jon
Posted a lot
Posts: 2,569
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Oct 15, 2016 19:10:12 GMT
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So I took a look at the belt today and concluded it was a bit slack. Went to adjust it, cue next problem. Adjuster bolt shears off, leaving a bit behind in the alternator. Not a problem I thought, I will just remove the alternator. All going well until the bottom pivot bolt. will it come out? Will it heck! It just spins, but won't undo and won't do up. I am thinking it has stripped the threads in the alternator housing, but how do I extract the bolt now?
Answers on a postcard! Space it limit, so can't even get a lever bar in to push on the end of the bolt whilst undoing it.
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Oct 15, 2016 22:12:20 GMT
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So I took a look at the belt today and concluded it was a bit slack. Went to adjust it, cue next problem. Adjuster bolt shears off, leaving a bit behind in the alternator. Not a problem I thought, I will just remove the alternator. All going well until the bottom pivot bolt. will it come out? Will it heck! It just spins, but won't undo and won't do up. I am thinking it has stripped the threads in the alternator housing, but how do I extract the bolt now? Answers on a postcard! Space it limit, so can't even get a lever bar in to push on the end of the bolt whilst undoing it. What year is it mate,early one's to 93 i think have a nut on the other end of the pivot bolt that will be spinning.You can just get a 14 mm spanner in there to hold it then undo from the front.Mines a 91 and is like that. Later ones are threaded on the alternator body and get stripped because they are awkward to line up and cross thread. If you remove the alloy inlet manifold support bracket (three bolts) you might make yourself a bit more room to get round the back? Once you get it out if it is a threaded alternator body type get a longer bolt and use a nut and lockwasher on it.Apparently if you buy a new alternator from Mazda none of them are threaded now anyway. They are a pig to get at,i've only done it once and that was enough ! |
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g40jon
Posted a lot
Posts: 2,569
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Oct 15, 2016 22:41:50 GMT
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It's a 91 and there is no nut on the other end anymore! No idea how long it has been like that for! Cheers for the info, that at least gives me some hope I might eventually remove the damn thing!
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Oct 15, 2016 22:49:18 GMT
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It's a 91 and there is no nut on the other end anymore! No idea how long it has been like that for! Cheers for the info, that at least gives me some hope I might eventually remove the damn thing! Yep,it should definitely have a nut on a 91 and the alternator leg won't be threaded.That might be half the problem as it would be vibrating about a bit i'd reckon. Should come out pretty easy,whip that bracket off and hopefully you can get at it. |
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sounds like you have a bad earth. check the big fat main earth that goes on to the chassis/body.
if your battery is well charged then id dismiss the alternator as a culprit for now.
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g40jon
Posted a lot
Posts: 2,569
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Oct 16, 2016 19:59:37 GMT
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So just to update, I finally got the pivot bolt out, what a mission that was! 2 hours of jiggling a spanner back and forth whilst levering the head of the pivot bolt with a pry bar!
Drilled out the snapped bolt and re-assembled after giving everything a good clean. belt tentioned up, freshly charged battery refitted and hey presto, working mx5 again! charging at a constant 14.5v, so I am fairly happy that it is problem solved!
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Oct 16, 2016 20:05:57 GMT
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Good stuff,have you put a nut on it !
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g40jon
Posted a lot
Posts: 2,569
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Oct 16, 2016 20:37:04 GMT
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I sure have! I don't fancy having to do it all over again any time soon! Cheers for the assistance HV!
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Oct 16, 2016 20:42:00 GMT
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Anytime fella,glad it's sorted !
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