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Weak a/c and heater

Old 04-12-2012, 03:56 PM
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Default Weak a/c and heater

Worked fine when I left the car in Oct.

Dad complained that the a/c wasnt working well a couple weeks ago, I called him silly.

Now that I'm driving the car again, I can say, yes, the a/c doesn't blow cold...but the compressor is engaging.

But, on top of that, the heater isn't blowing very warm at all.


I did a quick poke up under the dash and it appears all the ***** and pulleys are working, and if I do change from warm/cold or the different vents there is change in temp/flow.

But I have noticed that when i set it to floor, it will still come out quite heavily out the main vents.

Think I developed some sort of leak in the system somewhere?


My feets are cold the morning!!!! I don't see how I can possibly have low heater temps when the coolant is getting up to 180°F
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Old 04-12-2012, 05:04 PM
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Vacuum line disconnected/broken?
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Old 04-12-2012, 05:30 PM
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vacuum line to what?
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Old 04-12-2012, 06:38 PM
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Sorry, my bad. I thought the selector was vacuum powered, but I'm mistaken.
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Old 04-12-2012, 07:57 PM
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I don't know if the NA's have the same setup as the NB's. But check the cables coming from the hvac controls along both sides of the trans tunnel. I had a similar problem when I pulled my dash and put it back together (badly). There's a billion flaps that block the heater core on the driver's side and on the passenger side they adjust the air flow. Sometimes the levers that are connected to the cables get jacked up and needs to be manually moved around.

Check the link for pictures and a better explanation of what's going on:

http://www.miata.net/garage/heater_cable.html
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Old 04-12-2012, 09:16 PM
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Originally Posted by thegrapist
I don't know if the NA's have the same setup as the NB's. But check the cables coming from the hvac controls along both sides of the trans tunnel. I had a similar problem when I pulled my dash and put it back together (badly). There's a billion flaps that block the heater core on the driver's side and on the passenger side they adjust the air flow. Sometimes the levers that are connected to the cables get jacked up and needs to be manually moved around.

Check the link for pictures and a better explanation of what's going on:

http://www.miata.net/garage/heater_cable.html
Good idea, since Scott DID have his apart
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Old 04-24-2012, 11:17 AM
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I'm pretty sure all the flappers are working, but ill double check.

it was working for sure in Oct when I left the car with my Dad for winter. He complained and when I picked it back up in March it wasn't working well for sure.

I can move from hot to cold, and there is a bit of a difference. Recirc/outside works, I've verified that. I have noticed that when i move it to feet only it blows out of the main vents still, that's not normal.

the heater is barely getting warm, maybe blowing 60°F, well after the car reaches 170°F. The a/c is nonexisitent but the compressor is engaging.
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Old 04-24-2012, 11:22 AM
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Two plane tickets, a couch to sleep and your problem is as good as solved.
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Old 04-24-2012, 11:26 AM
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I have a really huge couch too, sleeps two confortably (if you spoon) and tends to be full of kitties.
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Old 04-24-2012, 11:37 AM
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i dont know if the miatas suffer the same issue as the FWD cars, but when our cars do the same thing, its usually debris in the air intake in the cowl area.
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Old 04-24-2012, 02:09 PM
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Mouse nest
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Old 04-24-2012, 02:10 PM
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didn't think of checking that. will do. blower blows at full steam, its just always pretty much ambient.
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Old 04-24-2012, 08:01 PM
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Just found the same problem with my heater, no ac. Brand new blower, blows hard, but never very hot. Engine temp hangs around 195.
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Old 04-24-2012, 08:06 PM
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Originally Posted by Braineack
didn't think of checking that. will do. blower blows at full steam, its just always pretty much ambient.
yeah the system isnt airtight (again in the 323) so when it cant pull air in from the vent and acrossed the heater/condesner assembly it pulls it thru every crack and opening in the system.
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Old 04-24-2012, 08:12 PM
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So, you're saying Brain has excessive air flowing through his crack?
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Old 04-24-2012, 09:09 PM
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There are 3 cables check them all, also are the clamps for the big black A/C (Don't know what it really is) box still clamped? Mine had rattled loose once.
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Old 04-24-2012, 10:10 PM
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Originally Posted by rleete
So, you're saying Brain has excessive air flowing through his crack?
No but id like to change it to that
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Old 04-26-2012, 07:15 AM
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My vote is for a mouse house somewhere preventing a flap or two from moving. Stupid mice need to die in a fire.
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Old 04-26-2012, 08:50 AM
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I thought Brain had kitties to take care of mice?
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Old 04-26-2012, 08:59 AM
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I was up under the dash yesterday. All the sliders have full articulation at the flappers.

the hot/cold will change from just below ambient (with a/c acitvated) to luke warm (with heater). Viewed from right side of center console.

I can watch the recirc slider open the flapper at the blower motor in order to source air from behind the glove box or up through the intake vent.

All the vent positions change. Viewed from right side of center console, verified flow with my face/hand.

so unless there's something else in the box behind the center console that might be stuck/blocked I dont quite see what the dealio could be.


The heater core inlet is hot as ---- and scolds me if it touch it. I can bare a few second on the outlet...so that makes me think the core isn't blocked.
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