95 No Front Heat (1 Viewer)

[elbobino]

Been trying to figure out my no front heat issues. Read as many threads as possible and troubleshooting all the recommendations. My HCV looks to have been replaced by PO, visually looks perfect and moves via cable when temperature selector is moved. The servomotor appears to work normally when temperature selector is moved as well, I can see the links and cable operating when I pulled the radio.

There is a small plug directly in front of the servomotor plug that is not connected and not sure if that might be my problem? Photo below is it circled in red.

I don't see where it could be plugged in though.

I've also flushed the heater core on two separate occasions and it's clean and does not seem to be restricted at all.

My next thought is to swap in a different climate control to see if somehow the temperature selector slider is at fault.

Anything else I might have overlooked? Any tips appreciated.

 

[EricG]

How's your engine temperature behaving? Is the lack of heat intermittent?

 

[thabruiser]

Has this happened over time or all of a sudden? An air pocket in the heater core can cause a no-heat condition.

 

[elbobino]

How's your engine temperature behaving? Is the lack of heat intermittent?

Has this happened over time or all of a sudden? An air pocket in the heater core can cause a no-heat condition.

I flushed coolant and replaced thermostat and burped the system via incline and those radiator no spill kits as part of baseline about a year and a half ago.

Scangauge shows my temps at 185-190 during normal operation.

It has not produced any front heat since I purchased it 2 years ago. It has been just blowing "room temperature" air through the front since purchase and gives good heat through the rear heater.

No improvement from the second go around of flushing the heater core and burping the system.

 

[thabruiser]

Any history of headgasket replacement?

I recently looked at a Tundra that had been leaking from the radiator with a similar no-heat complaint. After recommending a new radiator to solve a low coolant issue, the customer said," nah, it's been like that for 3 years. I just added leak stopper to it once a year and keep going..." long story short the customer stopped up enough of the heater core that it was ineffective in producing heat. Some people add that stuff (PO maybe?) And never say a word. The heater core seemed to flow ok on the Tundra too (flushed with water hose) , but it just would not blow warm, even with all the blend doors confirmed to be operating as intended.

 

[elbobino]

Any history of headgasket replacement?

I recently looked at a Tundra that had been leaking from the radiator with a similar no-heat complaint. After recommending a new radiator to solve a low coolant issue, the customer said," nah, it's been like that for 3 years. I just added leak stopper to it once a year and keep going..." long story short the customer stopped up enough of the heater core that it was ineffective in producing heat. Some people add that stuff (PO maybe?) And never say a word. The heater core seemed to flow ok on the Tundra too (flushed with water hose) , but it just would not blow warm, even with all the blend doors confirmed to be operating as intended.

No history on headgasket. PO had it for 4 years prior and only did oil changes/replaced starter. I sure hope my no front heat doesn't turn into a headgasket repair lol

 

[Malleus]

It'd probably be a good idea to put your year in your signature line. I'd bet it's a baffle operation failure. Here's the "big picture"

 

[thabruiser]

Agreed

 

[elbobino]

It'd probably be a good idea to put your year in your signature line. I'd bet it's a baffle operation failure. Here's the "big picture"
View attachment 2948450

So should I be able to verify mix door operation by removing the blower/fan and looking towards driver side?

 

[Malleus]

So should I be able to verify mix door operation by removing the blower/fan and looking towards driver side?

I forget where the damper is, and exactly how to get to it. The entire A/C service manual supplement is in the Resources 80 series section.

The manual says you have to remove the dash, and from what I remember of the last time I did this, (it's been a couple of years), you do (the whole thing - it's not hard, but it is time consuming; and you need the FSM for the dash removal). I'd start with ppg 15-21 (troubleshooting), first, and then, if you determine it's the damper, go to ppg 42-43. Those pages are for the servomotors which control the damper action.

HTH

 

[elbobino]

I forget where the damper is, and exactly how to get to it. The entire A/C service manual supplement is in the Resources 80 series section.

The manual says you have to remove the dash, and from what I remember of the last time I did this, (it's been a couple of years), you do (the whole thing - it's not hard, but it is time consuming; and you need the FSM for the dash removal). I'd start with ppg 15-21 (troubleshooting), first, and then, if you determine it's the damper, go to ppg 42-43. Those pages are for the servomotors which control the damper action.

HTH

Thank you for the guidance. I will try to tackle this on a weekend and update the thread in case my situation can help anyone else.

 

[Malleus]

You're very welcome. I failed to photograph the disassembly process, either time I did it, so your comments/photos would be very valuable.

 

[jpoole]

I'll throw it out there before you start major surgery that you may be able to get a sense of coolant flow through the heater control valve and heater core by measuring the pipe temps going in/out of each. Could be worth starting this with a cool system and then noting how things heat up through the warm-up process. May still be an under the dash problem but at least you can have more confidence that you are flowing hot coolant through the heater core.

 

[elbobino]

I'll throw it out there before you start major surgery that you may be able to get a sense of coolant flow through the heater control valve and heater core by measuring the pipe temps going in/out of each. Could be worth starting this with a cool system and then noting how things heat up through the warm-up process. May still be an under the dash problem but at least you can have more confidence that you are flowing hot coolant through the heater core.

Good idea. I will definitely try troubleshooting all options before taking the dash apart.

 

[elbobino]

Looks like after 2 flushes of the heater core it may call for a third.
Strange because flush produced pretty clean coolant and water flow did not seem to be obstructed at all. But figure it's still clogged as taking the advice of measuring hose temps seems to pointing that way.

Heater control valve hoses on both sides of valve get to about 150 degrees when open and much cooler when closed on the heater side. Bottom heater hose that comes out of firewall (90 degree hose) is showing 150-170 and top heater hose is showing 120 when engine is at operating temp. But the big tell seems to be the heater core temp. With the radio removed I'm not getting any temps over high 80s on the small portion of the heater core that is visible behind the servomotor via my air temp gun.

This flush I'm going to again use prestone heater core cleaner but leave it in longer for maybe 45 minutes. If anyone had better luck with a different product or contact time, please let me know, this is getting frustrating to fix lol

 

[vfrer]

How did you burp the system? The only way I could get mine good was to park on a pretty steep incline and run it. Could tell when it was good when the heat started working again.

 

[elbobino]

How did you burp the system? The only way I could get mine good was to park on a pretty steep incline and run it. Could tell when it was good when the heat started working again.

I had it on an incline for 30+ minutes with those no spill kits that attach to the radiator cap. I'm going to increase the angle of incline and just run it with the radiator cap off this time and see if I get lucky before flushing again.

 

[hl krawler]

You can get a cooling system pressure tester for pretty cheap, they can also be used to fill the system after youve done the pressure test. Ive seen some mechanics suggest doing it 2-3 times.

 

[jpoole]

@elbobino nice work on the troubleshooting. It's annoying that you still have to work on this but at least you may be able to avoid needlessly pulling the dash, which would be much more frustrating.

Heater core flushing is a topic universal to almost all autos so you can get some good ideas by surfing Google search and YouTube, etc... 30 minutes of that research may be worthwhile and give you a few more techniques to try this next time around.

Seems like whatever is blocking up the heater core is stuck in place and no longer flowing out into the coolant/water which is why you are seeing clean coolant even though you still have the blockage. You've got to loosen this crud up and get it flowing, without damaging the heater core or causing any leaks. I'd guess that mild acids and low pressure flushing/backflushing may be your best tools to use here.

I'd consider filling the heater core with white vinegar for 12 hours and then flushing with a water hose in both directions afterwards to see if that breaks anything free. Run the output of the flushes into a white (or similar) bucket so that you can determine if you are making any progress as the crud may be visible in the water/output. If 12 hours of Vinegar doesn't work I wouldn't be scared to go with 24 hours or longer. I've run vinegar in the full cooling systems on a few vehicles (including my 80) that really needed de-scaling/cleaning and haven't yet had any issues. If you open up a leak I'd guess that you were on the edge of failure anyway, but there's nothing wrong with easing into this to try to avoid causing new issues.

When flushing cooling system components out I typically just use tap water as it doesn't cause an issue unless it's really heavy and left in for a while. When you are done flushing/draining you can use a shop vac to move air through the cooling system and get most all of the tap water out before you refill with coolant. I typically go with blowing through the system but sucking works also. You can stick the shop vac hose into various openings in the system and leave it there for a while to ensure lots of airflow, etc.

You may already be committed one way or another but I'm in the green coolant camp as I like the increased availability and lower costs. I also do a partial coolant change every Spring as I think avoiding internal corrosion in the cooling system is a worthwhile goal.

 

[elbobino]

@elbobino nice work on the troubleshooting. It's annoying that you still have to work on this but at least you may be able to avoid needlessly pulling the dash, which would be much more frustrating.

Heater core flushing is a topic universal to almost all autos so you can get some good ideas by surfing Google search and YouTube, etc... 30 minutes of that research may be worthwhile and give you a few more techniques to try this next time around.

Seems like whatever is blocking up the heater core is stuck in place and no longer flowing out into the coolant/water which is why you are seeing clean coolant even though you still have the blockage. You've got to loosen this crud up and get it flowing, without damaging the heater core or causing any leaks. I'd guess that mild acids and low pressure flushing/backflushing may be your best tools to use here.

I'd consider filling the heater core with white vinegar for 12 hours and then flushing with a water hose in both directions afterwards to see if that breaks anything free. Run the output of the flushes into a white (or similar) bucket so that you can determine if you are making any progress as the crud may be visible in the water/output. If 12 hours of Vinegar doesn't work I wouldn't be scared to go with 24 hours or longer. I've run vinegar in the full cooling systems on a few vehicles (including my 80) that really needed de-scaling/cleaning and haven't yet had any issues. If you open up a leak I'd guess that you were on the edge of failure anyway, but there's nothing wrong with easing into this to try to avoid causing new issues.

When flushing cooling system components out I typically just use tap water as it doesn't cause an issue unless it's really heavy and left in for a while. When you are done flushing/draining you can use a shop vac to move air through the cooling system and get most all of the tap water out before you refill with coolant. I typically go with blowing through the system but sucking works also. You can stick the shop vac hose into various openings in the system and leave it there for a while to ensure lots of airflow, etc.

You may already be committed one way or another but I'm in the green coolant camp as I like the increased availability and lower costs. I also do a partial coolant change every Spring as I think avoiding internal corrosion in the cooling system is a worthwhile goal.

I've followed the HEATER CORE FLUSH-OWNED thread and watched plenty of YouTube videos to confirm I'm doing it correctly. My contact time with the heater core cleaner was only about 15-20 minutes each time because it came out clean, I thought I was good. So it does seem possible that maybe I havent loosened up the blockage just yet. I think I'm going to attempt burping it again first on a steeper incline to rule out trapped air. If I see no difference, follow your tip with vinegar and spend more time on the flush to make sure it's done long enough to unclog it