trochoid

iTrader: (6)

To add to Kentetsu's suggestion, connect the ground wire to one of the alt mounting bolts. Also, belt tension, deflection of a used belt should be no more than 1/2" total at the mid point between the pulleys.

To answer an earlier question about the firewall ground. I have mine run from a bolt hole on the passenger side of the tranny to an extra bolt in the firewall near the heater hoses.

ray green

iTrader: (14)

Thanks Ken, RW, dj and Trochoid, etc, I can't believe you still have patience for this (I wouldn't if I didn't have to).

I'll check everything over again this weekend, especially the belt, alternator and grounds (I'm betting on a bad ground). Neighbor Bobby thinks it a step down transformer in the gauge cluster, which operates at 7 volts, hope not, this would be a pain to replace.

A beer and lots of kudos to the one who gets it right. Hell I'll buy everybody a beer when I get this figured out.

twinkletoes

iTrader: (17)

Huh, did you get that thermostat housing or make it?? Looks good. I have those same excact battery tie downs, the first ones. Are you saying those first battery tiedowns you had are bad just because the kind or you had corrosion buildup?? I like them, because you dont have to unscrew the bolts to take off teh cable.

twinkletoes

iTrader: (17)

Wait a minute...id ont know if all batteries are the same like the positive being on the left and the right the negative. It looks like your cables are backwards or the battery is. And if you switched them on accident something would go wrong..

dj55b

iTrader: (2)

doesn't matter how you put it in there ( this is for the battery) and if his cables were reversed the whole car wouldnt run because he would of probably blew his fusible links (if he still has them)

trochoid

iTrader: (6)

Ray, I'm sticking with you on this one cause it has my curiousity peaked. If you have a DMM handy, you might check the voltage from the + post of the battery to the + post on the alt, do the same for the - battery post to the alt body.

ray green

iTrader: (14)

Will do, thanks Trochoid.

Rogue_Wulff

Also check the voltage drop from the battery to the car chassis.

Kentetsu

You still have the rat's nest Ray? How many belts do you have turning the water pump? I still think you're slipping

ray green

iTrader: (14)

OK I have some results on the headlight problem but it has taken awhile. First I had to deal with the damage that a local yocal tow truck with faulty and unsafe equipment did to my virgin front end sheet metal:



Details at:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/why-i-have-4-rx-7s-634341/

Then I had to get my mechanical water temp gauge installed:



Details at:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/second-water-temp-sender-tip-installation-question-631760/

And the data coming out of my lab this week has been hotter than an overheating rotary.

But I have done the road tests and the "overheating" problem is related to both the headlights and speed, but has nothing to do with the coolant temp, which holds at a constant 180 degrees, according to the mechanical temp gauge - it never even blinks.

So it sure looks like it's electrical, sorry Ken, I don't think the belts are slipping, but I wish that had been the explanation.

It "overheats" a little only when the headlights are on. A little at lower speeds, below 60 mph, and a lot when I'm out on the highway doing over 70, with the needle approaching the first warning line:



The good news, it's just a gauge acting up. The bad news, I still don't know what's causing it.

So any suggestions are very much welcome. I'll end on a positive note, here's a better picture of my Autozone cable ends, the positive one is really good because it has two good ports for the two + cables on our cars:

Kentetsu

Almost sounds like it's related to the power output of the alternator. The faster the alternator spins, the more power it can produce. This power output is supposed to be limited so that it doesn't burning stuff up, but maybe yours is bad? I think that would be the voltage regulator.

Maybe get some readings off the alt. At idle, midrange rpms, upper rpms. Then let us know what the voltage output was at each point. What d'ya think?

ray green

iTrader: (14)

Your the man Ken, I'll give that a try.

ray green

iTrader: (14)

OK, I did the multimeter tests and found that the voltage drops from 13.5 V to 12.5 V when the headlights are turned on, pretty much independently of rpm. So could this be the problem with the temp gauge readings?

I don't think it's the belt or alternator for the following reasons:



1. I had the same problem with the alternator I had in before this one.

2. I've had several belts in there over the last year, all in good shape and none with evidence of slipping, but none made any difference in preventing the temp gauge from going bonkers.

3. That belt is about as tight as I could get it, easily within the 1/2' rule.

4. When I do the headlights on test I'm standing outside the car, looking at the multimeter and engine bay, and that belt ain't slipping.

So more info, still no solution. Anybody got any more suggestions?

Thanks!

Ray

Kentetsu

I can't remember without looking back through all the posts, but does it do the same thing when just idling with the lights on? Or is it only when driving?

Have you tried swapping out the sensor yet? Maybe someone has one they'd be willing to send out to you out of good will...

kymber39845

I bet I have one in the donor car still...it was working fine when I parked it to part out in December...yours if you need it just tell me what it looks like...LOL
Kymber

ray green

iTrader: (14)

"I can't remember without looking back through all the posts, but does it do the same thing when just idling with the lights on? Or is it only when driving?"

I have trouble remembering too Ken and this post has gotten too long to read, but here's the answer to your question.

When testing the voltage output in the driveway, I get the same drop in voltage (about 13.5 down to 12.5 V) at 750, 2400 and 4000 rpm. In the driveway test, there is only a small corresponding increase in the temp gauge.

The temp increase out on the highway at sustained speeds of 80 mph, 4000 rpm, and headlights on, is much greater, approaching the first warning mark. Of course I don't have volt meter readings for this condition, but I suspect there is the same 1 V drop with the headlights on.

With the headlights off at highway speeds, I still get slightly higher temp readings than "normal", about half way up the gauge.

So it seems to be related to and aggravated by both a load on the charging system and a load on the engine (lights on at high speed).

"Have you tried swapping out the sensor yet? Maybe someone has one they'd be willing to send out to you out of good will..."

First thanks Kymber for the generous offer!

Yes Ken I did try swapping out the temp sensor for one from another car with no history of temp gauge problems, but it made no difference at all. Both sensors were in good shape, but I didn't test them beyond that. I could put in a new one (that's now on the list of things to do), but I don't think that's the problem.

"If you have a DMM handy, you might check the voltage from the + post of the battery to the + post on the alt, do the same for the - battery post to the alt body."

I'm not sure what I'm looking for with this test Trochoid, but I didn't find any voltage between the + post on the battery and the + post on the alt, nor was there an voltage between the - battery post and the alt body (as I'd expect, am I looking for some kind of leak?). There was also 0 resistance for these tests as well, so I'm assuming all the connections are fine.

Maybe it's the dash gauge itself? Maybe I should add a second after market temp gauge, electrical this time that replaces the original. Seems like I've tried every thing else.

I like your idea Ken that it is in the charging system, but I can't figure out exactly what it could be. I think I'll install a different alternator and put a new belt on (again) and see what happens. Any more ideas along these lines?

Thanks
Ray

Kentetsu

Okay, enough *****-footing around here damnit! lol. Let's start all over again....

First thing we should do is find the Truth. The gauge is claiming that the car is overheating, but I've heard that they can be very inaccurate, so I'm not sure if I'd be too quick to buy the story he's selling you. So, how do we find the truth?

Go to any grocery store, look in their kitchen utensils section, and pick up a simple dial faced thermometer. Now go out to your car (which should still be warm, unless you took too damned much time browsing the magazine section) and plug that puppy right into the radiator. Be careful here, as you don't want to **** here off or damage the radiator, but I believe you'll be able to insert (always ask her for permission first) the tip of the thermometer in between the fins of the radiator.

Placement will be critical. This type of thermometer uses a thermocouple, so it will read the temp from the first inch or so of the probe. This is the part that you will want in contact with the radiator metal. Make sure that it will not interfere with the fan, because you'll want to be able to idle/drive with the thermometer in place. Try to place it under the inlet, but down low enough that it will always be under the "water line".

Idle it forever in the parking lot, and get a maximum temp. Then drive it on the highway until it "overheats", and find a safe place to pull over and take another reading. This information should be useful in determining the value of the temperature gauge's testimony. Personally, I'm beginning to think the little bastard is making **** up...

ray green

iTrader: (14)

Now Ken, I trust my little Sunpro and I think it's right about this particular situation, the coolant really is at 180. But I just discovered some new and interesting information, my plugs are looking real hot (ie white)!

So that worthy Mazda original electrical gauge wasn't even lying, the frigging motor really is running lean and getting hot, but the coolant isn't.

So I'm looking into why the sucker is running so lean and hot, but at least I'm not wondering about the gauges and the coolant temp for the moment. Instead I'm thinking about a carb transplant.

Trochoid, where are you?

Ray

trochoid

iTrader: (6)

I'm here, been following this and watching for anything new, the white plugs certainly are. Is there any difference between T&L or front and rear on the plug color? How long have they been installed? Have you looked at the exhaust for any sign of overheating?

The plot thickens, as they say. If the engine was overheating, it should show on the 2nd gauge, in fact it should show above 180* occassionally anyway. The thermostat should be fully open by 180*, and above. I'm not fully convinced the stock gauge is reading true, mostly because of the electrical gremlins associated with it. Both gauges may not give the same reading, but they should follow the same pattern of rise and fall. Since the new gauge is mechanical, that takes the electrical gremlims out of it's reading.

As far as the engine running hot and the coolant not, can't happen. Can the engine run leaner and not overheat, yes.

ray green

iTrader: (14)

"I'm here, been following this and watching for anything new, the white plugs certainly are. Is there any difference between T&L or front and rear on the plug color? NOPE THEY ARE ALL REAL WHITE How long have they been installed ABOUT THREE WEEKS? Have you looked at the exhaust for any sign of overheating?YEP THE EXHAUST MANIFOLD IS LOOKING MIGHTY WHITE TOO"

The coolant temp, as indicated by my high quality sunpro gauge, holds really steady at 180, just a hair over the line when I'm pushing it, just under before I get it going. I'm inclined to believe it.

So you are saying I need to make a decision between my brand new sunpro and my 23 year old stock Mazda temperature gauge? They certainly aren't talking to each other. Tough decision, I'll have to sleep on it.

In the mean time I put in four freshened plugs and turned the mixture out a half a crank, I'll see if it helps in the morning.

Thanks for the help guys, this might be useful to you someday.

Ray

trochoid

iTrader: (6)

Turning out the idle mix screw will only affect idle, it will not affect afrs when running. You may be getting enough fuel to run, but run lean. If your fuel filter is good, check the filter screens in the carb around the banjo bolts on the feed lines.

Kentetsu

Damn, completely forgot about the new gauge you installed. Sorry man. But yeah, the white plugs kinda throw a new light on matters.

ray green

iTrader: (14)

Update 6:00 am. The drive in this morning was in the dark, one nasty wreck that makes you slow down a bit but otherwise pretty much normal, lights on, 80 mph and the stock temp gauge waltzing around just below the first warning mark, then returning back to more or less normal once I got off the highway.

The throttle response was improved though, I think I may have had it leaned out a bit too much in an effort to get a bit better gas mileage (Trochoid, I'm talking about adjusting the gas/air mixture screw, the one on the left, not the idle screw on the right). I'll check the plugs again this evening and replace the fuel filter, but the one that is in there doesn't look bad and is only a few months old.

We rebuilt the carb about a month ago so I'd be surprised if there was any build up in the banjo bolts, but this is easy to check and I will. In any event this temp gauge problem predated the carb rebuild and wasn't changed at all by the carb work, so I just don't see a connection.

So now I'm thinking the hot plugs and temp gauge readings are just coincidence, I still have some kind of mysterious problem with that stock electrical gauge giving bad readings. Like Trochoid says, it's hard to imagine the engine block temps and the coolant temps being that far apart.

Still, it makes me nervous - what if the stock gauge is working correctly and these temp fluctuations are real? They sure look like normal temp changes, gradual movement of the gauge that is closely correlated with the times the engine is working hardest and running hottest - highway speeds with the alternator adding a bit more to the engine load. Not hot enough to overheat or noticeably affect performance but still not right.

It's like having a teenager.

Again thanks for your insights and input folks, it keeps me thinking.

Ray

trochoid

iTrader: (6)

Ray, the external screws are for idle mix and idle speed, nothing more. They will not change the afs once the carb is off of the idle circuit. Since the carb was recently rebuilt, and I'm guessing the plugs weren't white before the rebuild, you may need to recheck the carb.

Did all of these issues start after the carb was rebuilt?

ray green

iTrader: (14)

Thanks Trochoid, I forgot, adjusting the idle mix screw won't affect the fuel mixture except at idle, so that can't be the cause of my white plugs. Obviously I need to go over the whole fuel system, which I will do this evening. Also I'll call neighbor and carb guru Bobby, who helped me do the rebuild, he can probably run down the white plug problem.

But in any case the headlights and high temp gauge problem doesn't seem to be related to the fuel issues, since it was happening well before the carb rebuild.

So I guess this simplifies things. Could a faulty temp gauge reading be related to the 1 V drop I get at the battery when I turn on the head lights?