Thompson Automotive


by Geary Morton

I just finished installing the factory cruise control in my '99 (NB) Miata and thought I would share some observations about installing the various components in an NB that differ somewhat from either what is written in Garage/Interior/Factory Cruise Control Installation, or the factory Workshop Manual.

MASTER SWITCH - There are two variations of this switch in the '99. One is for cars that have fog lights, and it has two push button switches in a single module. The other is for cars without fog lights, and it is a single rocker switch in the same size module. I mistakenly ordered the dual switch, thinking I would eventually install fog lights, only to find that it has a different number of pins than the connector on my non-fog wiring harness. Unless you want to do some cutting and splicing, order the right switch!

Also, if you are replacing the factory blank with a master switch, I would NOT go to the trouble of trying to release the blank by squeezing the hook clips from behind. It's nearly impossible to get to without dismantling lots of things in the way. Instead, I would pry and 'worry' the thing out from the front, even if you have to break it a little. You will find the connector for the new switch living in the back of the blank. Simply unplug it from the blank, plug it into the new master switch, and push the switch back into the rectangular hole, making sure you install it right side up. Once it clicks into place, it's there for good!

VACUUM SERVO - Installation is very much as described, except that there are only two fasteners - one bolt that goes into a threaded hole in the fender and one nut that goes on a stud that's already there. The servo I bought (on ebay) had five rubber grommets on its mounting bracket, but only two were used for mounting purposes. The others simply serve as additional cushioning. My unit was off an '01 and came with both the actuating cable and the vacuum hose attached (nice). There is a square plug in the firewall that pops out, along with a square knockout in the fiber insulating mat inside that is easy to push out. The cable simply snaps into this hole and can live there indefinitely until you're ready to deal with the pedals. There is also a support stud on the cable housing that snaps into a diagonal square hole on the inboard side of the brake fluid reservoir. The vacuum hose goes across the upper firewall and plugs into the back of the intake manifold. Mine had! a little rubber stopper covering the fitting on the manifold which I simply removed. What was a little confusing were a couple of support studs on an insulating sleeve that came on the vacuum hose. I couldn't find any holes that would accept these, so I went on ebay where you can find pretty good engine compartment shots of just about any car they might have for sale (good to remember). Anyway, I figured out that the '01 had the cable routed slightly different from the '99, and I simply used tie wraps to secure my hose in a manner that appears to be correct for my model.

CONTROL MODULE - The module installs exactly as described. If you have a Workshop Manual, it will lead you on a wild goose chase where you have to remove the key interlock mechanism. I have no idea what that's about, as this is nowhere near where the module mounts. I think it must be a misprint. The 'HOLD' indicator is actually a 'CRUISE' indicator on NB's (to the left of the fuel gauge), and it requires no special wiring for it to work!

STALK CONTROLS - This went pretty much as described with some minor variations. I chose to remove the air bag and the wheel. It's really not hard at all. The air bag comes off with just two 10mm bolts on the NB. I find that if you loosen the big nut on the wheel without completely removing it, you can then give the wheel a few good jerks to free it from the spline without shifting its position. After that you can center it carefully and gently remove the nut and the wheel. Next is the clockspring, and as long as you're careful not to turn it after it's removed , you won't have any problems. What was the biggest problem for me was removing the bottom panel under the steering column. It is secured by 2 Phillips screws near the bottom edge of the dash, and two 10mm nuts that are fairly difficult to get to. I found that the one on the left was easiest to access through the fuse access hole after I loosened the fuse block and pushed it out of the way. The nut on the rig! ht can be reached (with some difficulty) from behind the bottom edge of the dash. I used a small 10mm combination wrench on both. Once that cover is off, the connector is easily accessed, and the cluster switch is simple to swap out with the new one.

PEDAL ASSEMBLY - This proved to be the most challenging for me, as there were some differences in the assembly I bought on ebay and my existing unit. I decided it was going to be too much trouble to change out the bracket and both pedals (gas & brake), so I decided to make the newer fuel pedal work in the old bracket and simply replace the old stoplight switch with the newer stoplight/cruise switch. The problem was that the newer bracket had nylon bushings where the gas pedal pivoted and my bracket didn't. Newer NB owners shouldn't have this problem. The holes in my bracket were the correct diameter for the pivot rod, but no room for the bushings, and the old pedal didn't use a circlip to secure it. Instead it had a 'top hat' (for lack of a better term) press over the end of the pivot shaft. This had to be pried and 'worried' off with considerable foul language. After I got it off and tried to insert the new pedal shaft in the holes, I found that there was too much s! ide play, as the bushings in the newer bracket were shouldered and gave some side support. So, I had to find two washers that fit reasonably well over the pivot shaft and were about a thick as the shoulders on the nylon bushings. That did the trick. The only challenge after that was putting the circlips on the pivot shafts of the pedal and the secondary 'cruise arm' without losing them. I found that needle-nosed pliers worked well for this. Don't forget to put the pedal spring on (as I did) before you install the circlip. Oh, and the nylon bushings for the secondary 'cruise arm' fit perfectly in the original bracket. The cables simply snap into the pedal arm and the cruise arm, and I did that last.

The stoplight switch is easy to replace, and the new one should be adjusted far enough into the bracket that the switch plunger is completely (or almost completely) compressed when the brake pedal is released. If you don't do this, the cruise will not engage. Oh, the little two wire cruise connector can be found tucked away about 10 inches back up the stoplight cable. It took me 20 minutes to find it. It plugs into the stoplight switch next to the stoplight cable.

Finally, it's worth mentioning that the clutch switch that prevents starting without depressing is also tied into the cruise circuit, i.e. nothing to do here. It's already done. If you depress the clutch pedal, the cruise disengages.

I would reckon that my total time for this installation was about 8 hours, but part of that was due to the fact that I was/am slow, and I was having to discover quite a few things on my own. I'm very please with the end results. The cruise control performs exactly as you would expect from factory unit. Anyone interested in doing this mod is welcome to email with questions.

-- Geary Morton

Addendum to Geary Morton's Excellent Cruise Installation instructions

by mrsats

Removing the factory blank will reveal either a 10 slot/8 wire (as 2 blanks *) plug (Q-02) or 1 of 2 possible E4-01 plug being a 6 slot / 5 wire (as 1 blank) plug. This should be done before you order any parts as the existing wire harness will tell you how much rewiring is really involved in adding cruise to your car.

By removing the factory blank and determining whether it is a 10 plug or a 6 plug will be the first step in solving a lot of problems in the future, first by making sure you have the right switch, cruise only (6 slot E4-01), fog only (6 slot E4-01) or the combo switch for both fog and cruise (10 slot Q-02). If you only have a 6 slot and want to install a combo switch, make sure you order the harness for the switch so you can splice it in. I must mention that my cruise only main does not light up at the switch unless cruise is engaged, but that might be normal as direct power to the switch will not get the light to turn on, maybe is burnt?

If you have the the fog / cruise combo 10 slot plug as discussed, you should have a full plug and play cruise and/or fog system and is noted by the Q-02 cruise control combo fog switch... all the wiring should be there to simply plug your components in and be up and running with a simple adjustment of the brake switch as described by Mr. Morton's excellent instructions.

If you have the fog or cruise only 6 slot plug YOU MUST... REPEAT MUST make note of the wire colors. there were 3 different harnesses used in the 99-00 years, and can be identified by wire color.

A cruise setup harness will have the following wire colors, B, R/Y, B/Y, R/B, GY/R and 1 blank slot. Installation of Cruise with these wire colors should be simple plug and play, again with the brake switch adjustment as described by Mr. Morton's excellent instructions. from looking behind the plug (wire view.) X | R/Y | R/B B | B/Y | GY/R and all these wires tie into the X-07 instrument harness and you should be good to go.

A Fog light setup harness will have the following wire colors, P/L, R, R/G, R/B, GY/R and 1 blank slot. Installation of Cruise with these wire colors will require a little rewiring of the plug, and again the brake switch adjustment as described by Mr. Morton's excellent instructions. from looking behind the plug (wire view.) X | P/L | R/B R/G | R | GY/R this is for fog lights, you will need to rearrange or rewire the R/G, P/L and R from the switch to the X-07 instrument panel connector located just above the steering column behind the removable plate.

I rearrange the order... to keep it neat and use most of the existing wiring to: X | R | R/B P/L | R/G | GY/R this is done by looking down the front of the connector and pushing up on the plastic retainer at the top of the slot and pulling the wire from behind. the R/B and GY/R go to the instrument cluster through the X-07 plug just above the steering column, to show the dash lights on, I did not make any changes to these as they are for both setups, and my dash board cruise light works fine.

Now comes the fun part... we need to deal with the 3 wires, P/L, R and R/G to get them to match up with the cruise only wiring setup of B, R/Y and B/Y at the X-07 plug. With this fog wiring you are missing (physically missing) the R/Y connection to the the male side X-07 instrument cluster plug... its just not there, the B and B/Y is there and ready for cruise, but the fog wiring we have the P/L is in the wrong position in the X-07 connector slot (male side) as is the R and the RG, all easily fixed, sounds confusing, but its simple to deal with if you can find a connector small enough to work in the X-07 harness that is.

Because the R to my knowledge is fog only and I don't have fog lights, I removed it from the X-07 plug by poking up on the wire retainer and pulling the wire out of the plug... I inserted this into the missing R/Y slot of the male side of the connector so my newly positioned R (top center) corresponds to the R/Y connection of a cruise harness. This is absolutely required, and no other way I can figure to avoid it without going direct to the cruise control module. Realizing this was time consuming, and frustrating, I decided that the P/L which is a ground wire, I just cut it at the switch and dropped a short wire to the screw retaining the fuse box cluster (it was close and neat) and avoided the hassle of trying to relocate in the X-07 connector. Now for the newly positioned R/G located at the bottom center of our new switch layout, this is supposed to match up with the B/Y which is part of the cruise circuit running through the X-07 plug and tied into the ignition switch.... I hunted for this wire, its there but I could never locate where it went to, and by the grace of god, good karma, or just damn stupid luck, I didn't need it after all, as the R/G, also is tied to the ignition switch through the X-07 so I just left it in its spot and its relocation at the switch side connector works as its supposed to..

Out for a test drive... all is well in cruise mode, it works flawlessly... it will not allow me to engage unless I am around 40mph, and the dash light works perfect, switch, brake and clutch switches all disengage the system as they are meant to. Many thanks to Geary Morton for his original write up and for swapping wiring diagrams with me.

regards, Michael, aka Mrsats.

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8 October, 2008

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