On the way back from a long driving trip our heater suddenly blew cold air (08 GX460). We fiddled with the annoying auto vs manual controls but no warm air. Next day I ran the diagnostic climate system and got 00, it’s worked hit or miss over the last few days, warm then cold. So I ran the diagnostic again and got only a code 23 (Pressure switch). I’ve read all the other forum info and most say this is a low Freon or compressor issue. My question is, would low Freon make the heater not work as well? It’s 10 degrees outside so I have no way to check the A/C. Thank God for heated seats but we need a working heater. 🥶

 

Moved to 1GX forum. I am not a GX expert by any means, but this sounds like the valve/manifold that feeds the heater core is not opening.

 

The A/C does occasionally run in the winter, to remove humidity from the cabin air. Many 10+ year old GX's need to have their refrigerant topped-up. Take it by an Auto A/C shop and have them check the pressures.

A bad thermostat will cause it to run cold.

Also - do you have the correct coolant/water ratio? No idea what that would be for Colorado, but it's something that can be checked easily with a cheap gauge:

And of course, check the coolant level. When the engine is hot the level on the overflow bottle (next to the radiator cap) will be at the upper line.

Chip H.

 

[QUOTE=chiph9;10700743]The A/C does occasionally run in the winter, to remove humidity from the cabin air. Many 10+ year old GX's need to have their refrigerant topped-up. Take it by an Auto A/C shop and have them check the pressures.

A bad thermostat will cause it to run cold.

Also - do you have the correct coolant/water ratio? No idea what that would be for Colorado, but it's something that can be checked easily with a cheap gauge:

And of course, check the coolant level. When the engine is hot the level on the overflow bottle (next to the radiator cap) will be at the upper line.

Thanks for the advice. Will check coolant tomorrow. After I posted this I drove it 15 min and back for groceries, warm to hot air the entire time. Didn’t use the high fan though as that seems to cause it to blow cold air, but that may just be coincidence. It also seems to work better when outside temps are above 40.

 

... But it looks like you're the only one which guessed right, unless you just havent driven long enough for the engine to fully warm up.

A/C has nothing to do with bringing heat into the cabin.

 

When we first noticed the problem we had driven 12 hours and it had worked fine. As it got colder and later at night it started blowing cold air, very cold air, like having the AC on. It was probably around 12 degrees outside. The strange part is that it’s hit or miss with when it works. Definitely doesn’t want to heat up in the extreme cold even after 10 to 15 minutes of driving.

 

Checked the coolant today and it was low. Got it filled with correct premixed coolant for our area. We’ll see if it helps. We had an oil changed and everything topped before our trip so didn’t expect anything to be low. Makes me wonder what happened to all of that coolant. 🤔

 

Check for a leaky radiator. The plastic end-caps will crack after 10+ years (common age-related repair). Mine showed red crystals on the driver's side top.

Chip H.

 

Thanks for advice, first I realized I put 460 on original post not 470. No idea why I can’t seem to get that straight, guess I’m projecting that I wish it was a 460 with fold away seats. Anyway, sorry for confusion.
Heater is still blowing only cold. Did the diagnostic check again and only code that comes up is 00 so that’s not insightful. Added coolant and it appears to be staying level. Haven’t driven much since the air bag blew out and also waiting for conversion kit to arrive to replace. Lots of problems all at once. I did turn it to AC and that appears to work fine, freezing air and lots of it. Sadly at a high of 40 degrees I don’t need air.

 

Is it blowing cold on the driver's side, passenger side, or both? With dual zone climate control, there are 2 heater cores, one for each zone, could be that one side is plugged up, so be sure to check exactly where you're getting cold air, and if there's anywhere you aren't. Also check the 2nd row floor vents to see if they also blow cold, can help narrow down source of the problem.

The fact your coolant level was low, is very likely the reason for losing heat. You now need to make sure you get all the air pockets out of the system and get the level properly topped up, this can be done by getting the engine to full operating temp a few times and letting it burp the air out as it cools, drive around with the heat temp on full high (both sides) so the valve is all the way open, and it pushes any air out of the heater cores. The other thing you need to do is figure out where/how you lost coolant, check the rad for any signs of seepage/leakage, as it's a common item to fail on these trucks at this age.

 

You are absolutely correct it was the coolant. I’m going to admit to a very stupid mistake in hopes that it helps someone else that has the same issue. When I added coolant after an earlier suggestion I only added it to the overflow. I just didn’t realize because it was under the radiator cover that both could be low. Today I realized I needed to take that cover off and check the actual radiator and sure enough dry! Added over a gallon of 50/50. Ran the engine for 5 minutes and had heat! I feel stupid for not realizing that and now I’m getting the burbs out. I had assumed Walmart had checked the coolant level when the changed the oil but after looking at the paperwork there was no mention of coolant. Called and was told they don’t check unless asked to. So, could have been low for awhile or I have a leak. Don’t see obvious signs yet, but I’ll keep an eye out.
Moral of the story here is always check the simple stuff first and please all you mechanical Dads out there, teach your girls how their cars work so they don’t have to feel foolish when they don’t know how to add coolant to a radiator. 🤦🏼‍♀️

 

Glad to hear you found the cause of the no heat issue. Coolant levels don't drop like that on their own though, you've got some work ahead of you to figure out where it's going, or it's just going to happen again, and could cause additional damage next time. Watch like a hawk for drips under it, and give the radiator a real close inspection looking for signs of dried coolant (factory fill was Toyota Super Long Life, bright pink).

 

Also check the condition of the oil. Clear or dark - no problem. If its chocolate milk colored - you've got a problem. (head gasket)

Chip H.