Dashboard R&R to fix Heater Core

The heater core gave it up in the '90 at around 168K miles. Of course, it dumped the contents of the cooling system into the interior, making for a huge mess.

I decided to remove and hose down the carpet as well as change out the heater core. It seemed that the best way to do this was to remove the dashboard, which seemed a little daunting. It's actually pretty straightforward; as we all expect, the Miata is engineered for ease of assembly so disassembly should not be all that difficult.

The entire removal and replacement took a couple of weekends. I work at a somewhat slow pace and fixed a few things along the way that ate up a bunch of time. This included replacement of the indicator light in the cruise control switch, changing out the two lights in the radio that light up the LCD panel (put in LEDs instead as I could not find suitable bulbs), installing new heater hoses and "rebuilding" the heater box.

The latter was something that I could not have done without removing the dash. The presence of coolant saturated the insulating material and caused it to deteriorate on some of the "flappers" inside. Disassembly and re-assembly of this item is pretty easy. I used some insulating foam to replace the material I scraped off. Preparing the surfaces to accept the foam strips was a little difficult, but not rocket science. It took a little time to figure out what to do. Also, once the dash is out, all of these heating components are very easy to replace.

There were some items that I would like point out that may be of use to others:

  1. There is what seems to be a temperature sensor behind and to the left of the glovebox. I could not figure out how to remove the two connectors, so I cut the wires and replaced them with an inline connector. Even after the dash was off, I spent a few minutes and didn't figure it out. Of course, I was less interested at that point, as I already had cut the wires.

  1. There are three locations on the instrument cover that have clips that mate into the dashboard. Of the three, the two on the sides fractured when I removed the cover. I used an industrial glue to put them back together. I also used a pair of needle nose pliers and relieved some of the tension on the clips.

  2. When removing the dash, I suggest putting some sort of masking tape over the steering wheel. I gouged the wheel cover in a few places as some edges of the dash are somewhat sharp. I enlisted some help removing the dashboard, but put it back in by myself.

  1. I used a scissors jack to hold the steering wheel in place when I re-installed the two bolts. Not having the seat in the car was probably a pre-requisite to doing this.

  2. The tubing that pokes through the firewall for the two heater connections is very fragile. if you use pliers to break the hose connection free, you will likely crush the tubing unless you are very careful.

  1. Even though I asked the question and the parts supplier for the heater core assured me it was so, both sections of tubing were not included on the replacement core. The section that is fixed to the core was included; the section that connects via the short length of tubing was not.

  2. One good way to make an oval end of fragile tubing round again is to successively insert larger cylindrical objects into the end and re-form it until it is right. If you have a good selection of sockets, you probably will have the right ones to do this job.

Ken

Reply to
KWS
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Last oil change, I saw an early Miata in the shop with its dash out. Seems the owner wanted a *new* heater box due to the rotten foam (which apparently rots from age, coolant or no), and the assembly had to be ordered from Japan. I can't imagine how much the bill must've been--no doubt more than Blue Book on the entire car, which was a bit scruffy.

Ah well...I could envision an Ubercharger more than doubling the value of my own car. Sorta. In my less-rational moments.

Reply to
Lanny Chambers

Probably the thermoswitch. EM 6:14.

Of course, cutting through the carpet below the dash might be less visible than gouges in the steering wheel. :)

Leon

Reply to
Leon van Dommelen

Leon,

You humble me with your observations :-)

Ken

Reply to
KWS

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