Fault in my charging system, I think.

Technical Area Engine, Transmission, Exhaust etc
2

Rightio, this is a long story so I’ll try and keep it brief. Picked up my Eunos on Thursday. I knew it had a dodgy battery so would need a jump to pick it up, got that sorted. Broke down a couple of times on the way home but eventually managed to get a new battery in it and all was fine.

Fast forward to today, and about 30-40 miles later.

Went to drive back home from Ironbridge at around 10pm (around 15 miles, 2/3rds of which is along country roads with no lighting) and as soon as I put the lights on, the “CHARGE” and “HEAT” warning lights came on on the dashboard, the lights started getting dimmer and the whole car started to jerk violently, losing power catastrophically. Turning the lights off fixed it all and meant I could drive normally, I just couldn’t see.

So, there followed a hair-raising drive along 10 miles of country roads at 10pm, with no lights on the car. The only light I had to guide me was the light from the moon (thank GOD it was a clear sky) and the occasional flash of my hazard lights.

(eventually, a car came up behind me, overtook me on hazards and then drove slowly enough that I could follow his lights - he later pulled over and asked if I was alright, and agreed to guide me back home when I told him what was happening, what a top chap!)

So, anyway - the charging system in the car is quite clearly rollocksed. What’s the most likely cause? Alternator? Drive belt? Wiring? Why would a faulty charging system stop things like the rev-counter from working properly when that’s surely just mechanical? I didn’t think it would make the car jerk around either, I thought once the car was started the engine would run entirely under it’s own power without the battery being involved.

I’m going to have to try and trickle charge the battery to see if it’ll work, I hope I haven’t killed the battery stone dead as it’s a couple of days old.

Any help appreciated, I really don’t want this Eunos to turn into a money pit and I’m worried it’s going to :frowning:

3

G’day mate—

First check the alternator belt, may have slipped or snapped, hence the charge light. The tach is electronic, so may fail/jump about if you have electrical problems.

PS the alternator belt is the one that runs to the drivers side from the bottom pulley

4

 if the belts are fine then chances are it is the altenator gone.  i had this on an imported celica that used the same combination of dash lights to indicate a charging fault and as the battery was loosing the last bits of power (was driving it to the garage that i had already booked it into) the engine became veryu rough running and all sorts of things on the dash stared flicking around (revs, speedo, temp etc)

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Is the “HEAT” warning light coming on something else to be concerned about, or is that just likely to be the water pump not being driven because of the lack of power from the battery or something?

I’ve checked the alternator belts now and they all seem to be in good condition and turn when the engine is running.

Checked the voltage on the battery and with the engine off it’s at 11.86V, should that be 12V+?

With the engine running, but with no electric loads, it sits at 11.64V and with the headlights on it dropped to 10.75V. Those should be 14V+, right?

How much can I expect to pay for a new alternator? I’ve had a price of £382.50 from Halfrauds, and on MX5 parts they’re £350. This seems odd as other MX5 alternators are much cheaper?

6

The heat warning light os coming from the cat sensor, remove it and the light will go out.—

If the alternator is the problem ,which sounds quite likely, try Andrew at Autolink

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The heat light only ever comes on in conjunction with the charge light though, which makes me think the two are related somehow.

8

I’d worry about the charge light then re-visit any heat lamp issues that may still be present. They are for seperate systems but maybe there is a link that can affect them both.

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OK, I’ve got a used alternator from Autolink now (speedy service too, well impressed).

What needs to be removed from the engine bay before I can get access to the alternator? Just looks like a few hoses going from air filter to throttle body, does the throttle body need to come out too?