Hey all,

I finished the stock coolant temp gauge mod this Sunday, as promised here’s the story. It seems to be working well. OK, so it’s not as accurate as aftermarket but my dash still looks stock.

http://www.iluvmyrx7.com/3rdgen/how...gauge%20mod.pdf

My gauge now hit’s the second “C” mark as the thermostat opens at 180, is just above the “C” when the stat is full open (200), and is just below the first “H” mark at 221 (fans kick on low”. I’m not sure about this (the temps) exactly and will be double checking after I install an ECU.

I’m still fiddling with it a bit, but it definitely proving to be an eye opener. It’s amazing how long the engine takes to heat up and then how hot it will become before kicking the fans on! The stock gauge reads the same (just stands still in the middle) for something like 170 – 230 degrees!!!!!!

A few people out there asked me for pictures, instructions and the like. It’s all in the link above. If theirs is something missing, please ask. I’ll be happy to help you out if you’re stuck.

James

 

Cool, I'm glad it worked out. BTW, did you know that if you drive with your parking lights on, your fans should come on much sooner, I believe at 205-210 degrees. Care to verify?

 

Broken Link??

 

The link didn't work for me either.

 

Try this link

http://www.geocities.com/MotorCity/G...technical.html

 

This would explain what happened last night! I thought I was loosing it ... made me recalibrate the gauge when I returned home ... of course it was right on ... didn't need to be fixed. I can't say the exact temp, but yes about 10 or so degrees earlier.

 

What advantage does this mod have...other than seeing the temp move up and down more??? Is it just to see if the tsat is working propperly? Is it easier to notice when your engine is about to over heat? It seems that it will only touch the RED when its really hot linear or not. If my temp gauge started to move above the center, I would pull over anyway, because that's not normal. If I did the linear mod would I pull over only when the gauge touched the RED? Someone please give me some insight. Thanks

 

People do this mod to linearize their guage. This gives them an idea of how there coolant system is functioning. You can accomplish the same with an aftermarket guage (which I prefer since I like to see numbers), but some people do not want to clutter thier interior with an additional guage. It is all personal preference.

 

The stock gauge doesn't work worth a sh*t on most FDs. Ask trout. He'll be able to tell you all about it. I have already reached 230F on my autometer and my stock gauge wasn't even in the middle.
stock temp. gauge

 

Bingo! If I want exact numbers, I'll pull them from the computer ... air, fuel, and water temp.

 

rynberg, there was a thread describing the driving lights on, fan comes on earlier situation. According to one very knowledgeable member, it is true, he (or she) had a great explanation that i don't care to attempt to duplicate here.

 

Good thread (thanks). I'm about to do this mod, and I was wondering how many others had.

 

I know, I probably participated in that thread...

I was just informing James of that trick and was also trying to confirm at what temp they come on.

 

Rynberg, everyone, I just dug into the factory manuals for my car. 1994, Section “F”, page 135 and 136.

There is something called a “Electrical Load (E/L) Control System”. It’s hard to tell from the manual, but it appears to be mounted near the PCME. Basically it knows (is connected to) when the rear defogger, blower position 3 or 4, and / or headlights are turned on. If they are (on) it sends a signal to the PCME (Mazda’s acronym for an Engine Computer). I can’t tell what exactly it sends, but it looks to be simply grounding a wire. Anyway, the idea is that the PCME then increases the idle speed … to compensate for the load that the alternator places on the motor … to compensate for the increased electrical draw.

Now, mind you it says nothing about lowering the cooling fan trigger point, but I think that this is the case. It’s just too coincidental to not be. I.E. with the defogger, light and 3rd or 4th fan connected to it. Also, I found a thread where someone lowered the fan trigger point by disconnecting the rear windows defogger and leaving the switch on. In other words the E/L control thing though that the defogger was on and told the computer it was.

I started all of this reading hopping to find an easy way to drop the fan trigger temp. It looks like the idle speed will rise as a result … not so sure that I want that. I’m downloading the electrical diagrams for a 93 (couldn’t find em for a 94). If I see anything to the contrary, I’ll let you all know.

James

 

Neither my idle speed or vacuum changes with the lights or rear defroster on (other than a blip when they turn on). But yes, the general concensus is that the increased electrical load causes it for some reason. I look at it as a free and no labor involved fan mod. As a plus, it makes you more visible to other drivers (believe it or not I have been almost hit in this car more than any other car I've owned, despite the red paint and exotic looks).

 

OK ... I couldn't resist digging around for the E/L control box. I found it and the three inputs. I.E. one from the headlights, one from the rear defogger, and one from the blower. I cut the wire from the headlights and wired it to ground. Vouala! The headlights can now be on OR off and the temp set point for the engine cooling fan is about 10 degrees cooler. The idle speed is 100-150RPM's higher (when the lights are off), but it's not as bad as I thought.

I'm thinking of wiring this to a hidden switch so that I can connect it to the wire as per stock, or flip the switch and send it to ground. The idea being that I don't have to explain the mod to a mechanic who is trying to set the idle speed.

If there is interest, I'll post some more detail on how to do this.

 

If you play with the circuit deisgn just a little and measure your actual thermal sensor, you can calibrate your modified gauge so that the readings have real meaning. On mine I achhieved the following:

Hot mark - 251 F
High normal mark - 229
Center (no mark) - 190
Low normal mark - 152
Cold mark - 136

 

Guys i do suggest you get the new Billion Pro Fan controller. With this you can adjust the temperature your fan come in. You also have the choice of pluging in a separate temp. sensor. This controller has also a digital dispay for water temp.