- My model of MX-5 is: 1994 Eunos Roadster import 1.8
- I’m based near: _ London
- I’m looking for technical help or recommendations on: I am having some issues with my car. When I turn it on (especially when it’s cold) there’s a high pitch squeaking noise. (Lasts anywhere from 1 second to 30 seconds
This noise will also be triggered if I turn on the AC (on cold start)
A friend of mine said it’s the alternator pulley which is making this noise.
Do I need to replace the alternator or can I buy a replacement pulley?
How hard is it to DIY?
Have you checked the belt first? Sometimes spraying a little water on the belt that’s squealing can silence it. This normally points to worn belt or incorrect tension.
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We did and it didn’t happen however, sometimes it doesn’t happen. Its not constant and it doesn’t happen on every cold start
Why would the belt only make that noise on a cold start?
The rubber warms up and the noise dies down. Also as rubber belts wear the surfaces can become shiny or crack which is less grip. From memory the na uses an old skool alternator belt on a v pulley. There is an adjuster behind the alternator that allows you to add or remove a little tension.
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It sounds like it just needs a re tension or the A/C clutch is starting to seize? how old is the Aux belt?
M-m
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On a cold start the battery maybe lower so the alternator has to work harder to charge the battery hence the belt slips creating the noise. Turning the headlights on can exaggerate this.
I had the same squealing problem and a new belt and correct tensioning sorted it out.
D
PS How old is the battery? Maybe it’s starting to age.
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When it comes to tensioning I think the order is slacken the bolts that hold the alternator on, then rotate the bolt on the tensioner until correct tension is achieved then retighten alternator bolts. It’s a simple procedure from memory but it’s a long time since I did it. My mums tensioner was actually broken/stripped on a section so took a bit of bodgery back then but I got it right in the end.
I’m not sure as haven’t had time to check it yet. Got a new alternator belt on the way 
The battery has seemed to be completely fine and reliable. However, you make a good point because I took off my inlet manifold to get it powder coated (forgot to disconnect the battery) 9 days later I tried to start the car and it would (battery died) I jump started it and the alternator belt went crazy for about 3/4 minutes