Screw buying a board, just do this...





If you wire that up between the high beam switch and the relay up front, you don't need the cpu to control it.

 

What is the part number for the Dimmer Relay?

I tested the Dimmer Relay and it is bad. (Thanks Satch & Paulo for the info.) I removed the relay and managed to get it out of its rubber cover. Only to find there was no part number on it. (No part number on the headlight relay either.) Printed on the side is: "DC12V20A, TR., Imasen, OL 05"

There is no Dimmer Relay listed in the Parts Catalog at the Foxed.ca site. In fact, the Dimmer Relay isn't shown in the diagram of the car—it only shows three relays, not four. No number in the Wiring Diagram, or Technical Release books either.

So, I went to the Mazda dealership with the relays hoping the parts guys could help. They commented about the relays not having parts numbers on them, but looked for it but discovered there is no Dimmer Relay in any of their parts listings. (I'm pretty sure it's the same Parts Catalog as on Foxed.ca.) I explained about the convertible having a number of parts unique to it--and that it has 4 relays. Told them the Workshop Manual shows all four and even shows how to test the Dimmer relay. They looked doubtful. But forged ahead.

They looked at Ford parts as well as Mazda. And ultimately, they found a blue relay and asked if the photo looked like the relay I needed. We compared and I said it looks like it, but it's hard to tell because I couldn't read the configuration embossed on the bottom by the pins to be sure. Where did they find the part? He was looking on Ebay! Eventually they gave up and suggested that I use Ebay.

I went to the O'Riley and CarQuest stores and they couldn't help without part numbers either. (Even though I had the physical relay to compare. Arrrrgh!)

Satch, Paulo, Jack, Anybody, can you help a fellow 'vert owner and provide a part number for the Dimmer Relay? Maybe suggest a source for relays if you can? (Mazda wants $40-some dollars for a headlight relay!)

This is making me crazy.

I really appreciate your help.

 

As stated earlier, you can use a universal automotive relay found at the local auto parts store.

 

Found on Amazon:
H302-67-740 Exactly the same same relay as dimmer relay except for markings.
Genuine Mazda Part
Markings:
H302
DC12V20A
TR
Imasen
1K-18

FYI:
Headlight Relay
Found equivalent, complete with rubber cover & bracket @ RockAuto.com
Airtex
1R2501
H430

 

Replaced the FC66 CPU's large board (Horn, Key, etc.). It looks slightly different from the one I replaced, so fingers crossed. It fixed the high beam problem! (Hot Damn!)

Before I buttoned it up, I tested everything I could think of that it controls: Key in ignition, Horn, Seat belt buzzer/timer, Headlight Relay, HL Retractor, Lights reminder, Door Lock Switches, trunk switch, and they all worked. So it's looking good! Gonna take a test drive tonight when it cools off a bit.

Some suggestions: The CPU case plastic is getting brittle. Go gently prying the back off. Insert a small screw driver between the sides and the back and pull open a gap to free the side tabs. Then the top. Gently pull up and out. The tabs broke off easily. Beware! The small screw will strip the receiving threads easily when you screw it back in. The top hanger/holder that attaches the case to the body must break easily because 1/3 of the top was missing & broken off when I removed the nut that holds the case in. It is 25 years old.

 

Interestingly, replacing the CPU fixed the light for the ignition switch!

I wonder if the driver's side door lock light will work if I replace the bulb? Nah! Not gonna pull off the door panel to find out.