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Ok so my car has no heat for like 20 minutes or so. So I flushed the heater core and same thing. Once the car is warm then heat will flow. I am guessing this is because of my thermowax or whatever the name is. So I also recently bypassed the throttle body of the coolant line. So after doing a little research I see that I can remove the spring from the thermowax unit and re-install the screw so the thermowax is bypassed it looks like. Hopefully this will allow the heat to turn on when its cold or at least I am hoping this is what is causing it. My idle was a little higher then normal as well I noticed when it was cold also. Here is a website with pictures if anyone is interested. This is on an RX7 FD, but as far as a picture of the mod it is the same. ( https://www.rx7.org/Robinette/throttle_body_coolant.htm. )
If anyone has any other information they would like to share or pass on feel free. Thanks.
Ok so my car has no heat for like 20 minutes or so. So I flushed the heater core and same thing. Once the car is warm then heat will flow. I am guessing this is because of my thermowax or whatever the name is. So I also recently bypassed the throttle body of the coolant line. So after doing a little research I see that I can remove the spring from the thermowax unit and re-install the screw so the thermowax is bypassed it looks like. Hopefully this will allow the heat to turn on when its cold or at least I am hoping this is what is causing it. My idle was a little higher then normal as well I noticed when it was cold also. Here is a website with pictures if anyone is interested. This is on an RX7 FD, but as far as a picture of the mod it is the same. ( https://www.rx7.org/Robinette/throttle_body_coolant.htm. )
If anyone has any other information they would like to share or pass on feel free. Thanks.
The vehicle will not blow hot air through the vents until the car has warmed up, as for taking 20 min that might be another issue. If you have a thermostat that has stuck open then it will take longer to warm up and in return longer for the car to blow hot air. There are to many variables. Make sure the coolant is full, no air pockets in system and make sure the thermostat is working correctly. My 87 na takes 5 to 10 minutes of warm up time in the morning to start blowing warm air, once the vehicle gets to operating temp it will blow hot air (so hot you cant stand it).
Did you only flush the heater core? How did you do that...a reverse flush? Afterwards, did you top off the heater core? As littlebit suggested, the thermostat could be stuck open or the coolant system may still have air pockets. Most modern replacement thermostats have a fail-safe that will stick open when the device fails. This would prevent an overheat condition. A good indication that such a fail-safe device works is the longer time the car takes to achieve normal water temps. This is because the cooling system is stuck in an open loop. If you want to take a precautionary measure, replace the thermostat (after checking coolant levels), change the upper and lower rad hoses, and install fresh coolant.
I flushed the heater core in both directions with a water hose. I did not top off. I left the water in there. I thought that was ok. When I jerry rigged the thermowax that did not thing for me. I was working on some other things with the car like gauge pillar and a new tablet messing with my adaptronic ECU. Later when it got cold I let the car run and it was quite warm however no heat. The thermostat was replaced last April with a cooler thermostat. I learned that doesn't do much when trying to fix cooling issues lol. All radiator hoses are fairly new as well. I will burp the system and take a closer look sometime this weekend.
Has the car ever had good working heat since you've owned it?
An OE 180 degree thermostat is a must.. as has been suggested, it could be stuck wide open. However, even if that were the case, you should still have something resembling heat..
With the ignition on and engine off and blower motor off, doors shut, and the temp slider all the way on cold..slide it all the way hot. You should hear the servo for the water valve on the drivers side of the heater box actuating. It takes a good twoish seconds to move from full cold to full hot position. If you hear nothing at all, the logicon or the servo are suspect. If you do hear it moving, get under the drivers side dash, remove the nut vent and duct and the heater core access cover and do the same test while watching the servo operate the valve to make sure it's actually actuating it. If this passes as well, then I'd say your heater core has packed up for a permanent vacation.
However...
If this loss of heat was sudden.. and by sudden I mean it worked yesterday, but today nothing, it will almost certainly not be the core as the mode of failure for the core itself is a gradual loss of performance with use over time, or it worked when the car went into storage five years ago but now it doesn't.
A sudden loss of heat after you've been working with an open cooling system would have me leaning more towards air trapped in the heater circuit. So naturally I'll pose a few questions to you..
How did you bleed the cooling system? This isn't rocket science, but one or two mistakes can give you these problems. If you don't own one already, I strongly suggest you invest in a Lisle spill free funnel kit. This is like a funnel/bucket of sorts.. you use an included adapter to attach to the filler neck, and the funnel compression fits into the adapter. You can mostly fill this large funnel with coolant. In doing so, you achieve a true high point in the system to which air will naturally seek and burp from. It also will give you expansion room for the coolant which means virtually no mess. If you dont have a spill free funnel like this, you can just leave the filler neck open.. but be prepared for a potential mess.
The next thing I'm going to ask you is whether or not you had the temp slider on full hot when you burped the system. If not, then the previously mentioned water valve was shut and that prevents both coolant and air from circulating through the heater core and you may air lock the core until its put right.
Did you squeeze the upper and lower rad hoses both individually and simultaneously as the engine warmed up to help disperse any stubborn air bubbles ?
Lastly, did you allow the engine to cool back down entirely after the first burping and then repeat the process? Doing this helps any churned up bubbles to sort of collect again and rise to the highest point they can, and at that point you can be reasonably certain you will get them all out.
A spill free funnel isn't absolutely necessary, but it's actually one of my favorite tools in my arsenal. It's unbelievably effective, makes no mess, and allows you to really work all of the coolant hoses as well as give you easy visual confirmation of air being expelled and when its all gone.
So in summary... make sure you've got the right thermostat, properly and completely bleed the system of air, and make sure the electrical and mechanical components of what gives you heat in the cabin are functioning. Do it in that order. If still no heat, replace the heater core and that should almost certainly fix it.
Thanks for the ideas guys! So I burped the system and still nothing. The hoses were cold going to the heater core. I had recently bought a used controller and replaced mine. I had an idea that might be bad. So I put my old one on and voila I had instant heat. I only replaced the old one due to busted up clips to secure. So I pulled the board old of the old one and put it in the new one and now I have heat and it is secured good also. I guess that heat cool switch was messed up. The weird thing is when it was warmer out side I would move the slider from hot to cold and feel warmer air vs cool air So i figured that was good. I will probably burp the system again while running the heat since it is now working. I will save that for tomorrow probably.
The thermowax has nothing to do with the heater system, absolutely nothing in common but the coolant..
Your problem is going to be either:
-poor flow through the bungs on the block or the hoses
=faulty water control valve
=clogged core
=air trapped in system
Not sure if you mentioned it before but does it take 20 minutes for your temp gauge to reach normal too?
I get heat from my vents within the first mile of driving, long before the gauge has started to climb and think the FC has one of the best heaters I've ever used.
I'm out of the area for now but would like to check out that logicon board. In the mean time, I have a post about measuring the resistance of the sliders. Check it out and see if it helps your situation.
Thanks for the information. It turned out to be a faulty board.
Not sure if you mentioned it before but does it take 20 minutes for your temp gauge to reach normal too?
No the temp doesn't take that long to heat up.
Just quit with the thermowax, it's a dead end.
Yeah I just saw the thermowax was just causing my idle to stay around 1400 rpm is all. I have disabled this now as well.
Well I did have a class many years ago. I soldered the windshield wiper part to fix that. Of course it is broke again. I have decided to live without it as far as the intermittent wiper. I would say they aren't that great, but I can make do I guess lmao. The little soldering jobs are tough for sure. I will take you up on that when you have some free time on a weekend on something like that maybe. Always good to meet another rotor head and talk about them some too. There is not rush of course. I am free usually Saturdays after my class and Sundays as well if one of those days works for you. I took the car to class today and it ran great. I also had heat pretty as well pretty quick. I did put an after market fan in this thing a year or so ago. It doesn't seem to do that great, but to tell you the truth not sure the stock one did either. It does the job though.
I can easily fix that solder joint in no time. In fact, the repair will take considerably less time than the drive from Va Beach to Suffolk! If you'd like we can knock it out this coming weekend. Sound good?
My car has heat now that I changed the faulty logicon board out. I did not change out the thermostat. George things it is a bad solder joint that caused the issue and offered to look at it since he is local.
Values for this slider measured:
Cold (full left): 5kΩ (4.99kΩ actual)
Warm (mid-range): 2.5kΩ (2.6kΩ actual)
Hot (full right): 0kΩ (0.03kΩ actual)
This logicon front panel should be good to change the cabin temperature without any issues. Make sure to test the entire function of the front panel before reinstalling the logicon into the dash.
11-22-17, 07:36 AM
1988 RX7 S4 NO HEAT for 20 min!
Logicon Front Panel Solder Joint Repaired
