Hey everyone. I have a 90 Loyale 4wd 5spd. Just wondering if anyone else has issues with the windows fogging up all the time? I have good heat and everything, and even applied rain x anti fog to the glass which helps a little, but the windows still want to fog up even with the defrost on full blast. Any suggestions? Thanks.

is your a/c working?

I have the same problem with my 84 GL wagon and figure that maybe the conduit may be leaking which causes low output from the vents. Fan works on all speeds.

Does the ac work?  Without the ac working , it takes a lot of heat in some conditions to defog.

Other possible cause is coolant leak from the heater core, but that should be accompanied by a sweet smell.

If the carpet is wet (common this time of year) the moisture can cause the windows to fog up all the time. Is the car dry inside?

Leaking heater core?

 

Do you have to add antifreeze all the time?

 

Good luck,

Sam

I asked similar questions on the facebook page.   My car is later though (1999).

A lot of people were suggesting the windshield seal or rust holes in the firewall.   would those apply to you?

I am still trying to find my own leak.

I just had this problem a while back and found that a vacuum line had come loose in the engine compartment.  The line is in front of the passenger area under the hood.  Check around to make sure the lines are all connected.

Yes, the air doors are activated by engine vacuum.   See if the air is directed properly in the various settings.

Heater core is fine. No antifreeze in floorboards. No water in floorboards. Dry inside. Fan works on all speeds. Heat comes out the top of the dash to defrost, but its almost like it cant keep it warm enough compared to the outside air to keep it from "sweating". Vac lines and everything work properly, although the heat is hot, but in 30 degree weather and less its not impressive hot. It will defrost at idle in the mornings, but fogs going down the road for 10 or so minutes.

IS the engine thermostat 190 degrees F?  That is stock temp.  and the heat air temp is pretty good.  I have a 180 in one of mine, the heat is noticeably not as powerful.  Also, verify if the door that selects fresh VS recirculated air is working.  Normally, for any heat or defrost mode it should be bringing in fresh air.  Another thing I have modified, I can switch it independently - if you run with the door on recirculate, the windows can fog.  I only use the recirculate for the first few minutes from a cold start outside in winter.  A/C Max is the setting that puts it in recirculate normally.

 

Another thought - if the engine is running at stock temp [190] and everything else above seems normal, have mice ever been in the heater system?  They could have removed the sealing foam from the blend door and you won't get full power heat due to leaking.

Okay so to add another piece to the puzzle. It is a 193 degree tstat(OEM temp). Just to test, it does not fog with the temp select on cold and defrost full blast. Only with the heat on. And there is a noticeable "fog" that comes out the vents. Is it possible that the heater core is leaking just enough to cycle vaper through the vents but not actually leak into the floorboard or make the antifreeze level noticeably low over a few days?

Yes it is possible. If it is coolant coming through the vents try it on defrost. The "fog" should leave a greasy film on the inside of the windshield if it really is coolant. Antifreeze fumes also have a sickly sweet smell that is very noticeable.

Edited December 12, 20187 yr by Crazyeights

That description does make it sound like a very small leak in the core.    The heat "on/off" - if you mean the temperature slider, it's just routing more or less air through or around the heater core, so if the fog was coming from the heater core, that is exactly what would happen.

That's what I am going with. Tired of wiping the windshield every 10 seconds to drive. I will replace the heater core over the weekend and update.

Have the heater core out and it's definitely leaking. Waiting on the new one to arrive. Parts store had to get it via fedex. Pulling the dash was a fun adventure. Hopefully this will fix the issue.

If you found evidence of the core leaking, that would do it.  Yes, pulling the dash is "fun".  I had to do one to clean out mice nest destruction.

Theres evidence of the same in this one. All kinds of junk stuck to the core. Cleaning it out since im already in it as well.

Quick question Dave T. Since you've been in depth under the dash I am wondering about the connection between the 3 boxes (Heater core to AC, AC to blower motor). I pulled the clamps on both sides of the AC box to give some wiggle room. Now I can't remember if they fit one into the next and then clamp down, or if they just butt up against each other and the clamp is the seal between them. Thanks in advance for any help.

Pretty sure they just touch.  The clamps had foam on them iirc.  

That's what I was thinking. The bolt holes don't line up correctly otherwise. The foam is pretty dried out there and elsewhere. Would the simple foam adhesive backed weatherstripping from somewhere like walmart be an acceptable replacement?

I used some from a hardware store.  Just went after whatever type looked the most long life / weather extreme.  Try to get close on the width and thickness.

Driving to work this morning about 40 degrees out. No more windshield fogging. I did clean all the residue off of the windows and seems to be alot better. We can consider this thread resolved. Big thanks for the suggestions from everyone.