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BroncoHauler 09-25-2014 08:57 PM

Re: Heater valve bypass to fix "heated dashboard vents"?
Yep, even took it to SMBw to ask them to install it. They talked to somebody at the local Ford dealer, and they said 'don't bother, Ford already installs them'. Fro what I've been able to find, that is not true. There is a factory valve, but it does not shut off completely, so there is always some hot coolant flow through the heater core.

I still have it, since I couldn't lay my hands on it when I sold my SMB (I never mentioned itor advertised it as being included). I'm almost positive I know where it is, and I'm fairly sure I can dig up the instructions.


86Scotty 09-25-2014 09:38 PM

Re: Heater valve bypass to fix "heated dashboard vents"?
This may or may not help any. It's a fairly lengthy thread. I read it awhile back and looks by the title like it's not your problem. However, if I remember right there is a lot of good info about how the system works. Hope it helps, I did NOT just reread it all but will soon.

Also, this:


oldbonesclimber 09-25-2014 10:28 PM

Re: Heater valve bypass to fix "heated dashboard vents"?
I installed the Cold Air Rush with MAX Assist. Can't be happier. The A/C air with my Starcool is almost Too Cold traveling in 100 temps. Installation is a pain at the heater hose and needed some creative hose work. I would definately do it again.

Paul :u1: :u1:

carringb 09-25-2014 10:38 PM

Re: Heater valve bypass to fix "heated dashboard vents"?
My vents are also warmer than ambient. Barely when empty, but after a hard pull in the mountains, quite a bit hotter. I never did the upgrade because I usually drive with the A/C on, either because its warm or because its raining and DEF is needed anyways, or anytime most of the seats full I have to run the rear A/C to keep it from getting stuffy.

There have been a few time this summer though I wish I had it. Mostly, after a hard pull then stopping for a light or traffic. At that point, my coolant is a good 30F hotter than normal, and so is the dash air! And, there's been a few hard long pulls this summer I turned off the A/C when my trans temps topped 200F and the summit wasn't in sight yet. Then again, I'm still diff temp limited so I probably could just leave the A/C on and slow down a little.

So... I guess this mod will stay on my ever growing to-do list :b1:

Viva 09-25-2014 11:53 PM

Re: Heater valve bypass to fix "heated dashboard vents"?

Originally Posted by oldbonesclimber
I installed the Cold Air Rush with MAX Assist. Can't be happier. The A/C air with my Starcool is almost Too Cold traveling in 100 temps. Installation is a pain at the heater hose and needed some creative hose work. I would definately do it again.

Any tips for those of us who haven't done it and are not machine shop owners or fabricators? Where is it on the scale of "it's not too bad" to "if you have to ask..."?

It's great to hear you are happy with it.


JWA 09-26-2014 05:40 AM

Re: Heater valve bypass to fix "heated dashboard vents"?
Let me attempt to consolidate some info about the Ford HVAC systems.....

The following assumes the air circulating system is in good working order and functioning as designed.

Via the blend door hot coolant is now constantly present and circulating through the heater core regardless what setting is selected on the function control, aka Heat, Vent, Mix, Defrost, A/C or Max A/C. As such we feel vented air above ambient because the plenum is always heated. No way around this sad to say.

Adding some sort of coolant shut off valve in the coolant line off the intake manifold solves this problem IF we don't need the defrost function. It should be noted the Mix & Defrost settings not only direct air flow to the windshield and side window vents it engages the A/C compressor in order to dehumidify the air flow hitting the interior glass surfaces.

Stopping warm coolant flow through the heater core does reduce vented air temps but it also affects the Defrost function. Carefully consider this for any modifications begun or contemplated, think if this would be an inconvenience or safety issue.

That being said I'm somewhat in process of "field engineering" an electro-mechanical system that would give me control of a vacuum actuated valve via dash mounted switch. This would give me total control of coolant flow through the front heater core, I could turn it on or off at will, completely independently of the factory function controls. I have a general idea how to best accomplish this but the real test will be sorting out the actual details and making it work as I envision, the mechanics of it all so to speak.

I've already successfully developed a system for an after market rear heater which differs greatly from Ford's design for their own rear heat & A/C units. Ford has the rear heat Tee'd into the front heater core whereas my design allows for front heat only OR hot coolant flow directed first to the rear coil which in turn feeds the front coil. Because coolant flow can be directed according to need (front only or front & rear combined) its highly efficient for people and materials needing heat during the colder months front and/or rear areas.

This isn't all that complicated to me but I'm somewhat of a tinkerer, have plenty of necessary tools and not too shabby with wild concepts being put into action. The Max Air system consists of the same sort of components I've used and incorporated so for me it would a no brainer so to speak. For those who've not dug into routing and re-routing heater lines along with vacuum or electrical controlled valves this might be a bit daunting, at least initially.

The best part is all this is its mostly relatively cheap heater hose and clamps along with readily accessible automotive type coolant flow fittings. For the most part almost anything done can be easily reversed, in that way you'd end up no worse or better off than the existing conditions of higher-than-ambient air flow out of the vents.

Ask any questions and I'll do my best to answer them as clearly as I can.

Viva 09-26-2014 10:05 AM

Re: Heater valve bypass to fix "heated dashboard vents"?
Thanks for that explanation. I wondered about the AC/Defrost connection. I have to say I prefer a system that is more independent such as my typical cars have been. That is, a temperature function, a button that lets me turn the AC on or off (but does not tell it where to exude from), and a selector from which I can tell the air (hot or cold) where to come out from. I mean seriously, I'm not so stupid that I couldn't put AC on the windshield if I needed it to help defrost. OTOH, I don't necessarily want the AC compressor on when I'm towing up a hill, and I might like the AC to come out a specific position....

Okay, got that over with. Anyway... I think I might have two issues, but perhaps you (or someone) could give me your thoughts. Since I'm traveling, I don't have a good/known mechanic, so I usually try to either do my own repairs, or at least know exactly what I want done (if possible) if I'm taking it to someone I don't know (OTOH, if I had a good/known mechanic, it's not that I need or want to do this work myself!).

Anyway, so after reading the links that 86 Scotty provided to FTE (thanks!), I think I have both of the following:

1) The vent/heater core/design problem, and...

2) Perhaps a vacuum problem. I think the vacuum problem is a minor one, not a complete failure.

Symptoms of #1 are heated air coming out the vents even in cool weather (especially after stopping, but all the time to some degree), and a general area of hot air coming out from under the dash above where the Scan Gauge plugs in. Also although the AC always works, it seems less than icy in hot weather.

Symptoms of what I think is #2:

a) One time when I was towing and had the AC on (or actually it might have been the vents since I don't typically go uphill towing with AC on - - this might have been before I gave up on the vents), I was accelerating up a hill and everything automatically switched over to "defrost" position, then "mysteriously" switched back. This happened a couple of times last May, but then never again. I did wonder how it had "healed itself." Now I think I know: I have quit using the vents as they are so uncomfortably hot, and I typically now just switch the HVAC to "Off" when climbing a hill while towing.

b) I have had an EGR code (0455) set from time to time but with growing frequency. I had part of the EGR system replaced (for some annoying reason they didn't do it all but didn't tell me until I was on my way out the door and sure enough, about 50 miles later.... 0455). However now I think it might be (at least partly) due to a vacuum loss under acceleration. Because I thought I had noticed that it would often set if I was climbing a hill but midway up let off the gas slightly. Then "bing" I'd get the CEL and Scan Gauge would show it to be 0455 (I'm also getting occasional 0401, but I think that is separate?). The 0455 has been getting more frequent (but I did just finish a 2,000+ mile mountainous tow, so lots of accelerating up hills).

From what I read in the links, there is a hard-to-access vacuum canister and an impossible to find check valve. If Ford fixes these it's thousands of dollars plus (almost worse, to me) they take your whole dash, etc. apart. I find that often leads to annoying scratches, loose parts, etc. Anyway, when you are accelerating hard that pulls a lot of vacuum and so if there is a leak or problem, there is not enough left over to "run" the HVAC selector system, and so it goes to its default position, which is Defrost. Apparently the EGR system also uses vacuum, hence my hunch in (b), above.

I figure it must only be a smallish leak, not a complete failure, because I only notice it when towing/accelerating uphill, and also when I turn the HVAC selector from Off to another position, I can hear the "hushhhhh" vacuum sound (plus a wee squeak). So that must mean there is at least enough vacuum to run it most of the time.

I think this is separate from the "heated vents" problem as that occurs all the time, just by virtue of the engine running (no need to be towing, going uphill, etc.). So I likely need to fix both. It seemed like the best fix for the vacuum system was to make your own, generously sized canister out of PVC and mount it above the passenger footwell, along with a check valve, bypassing the original system. Some folks cut a hole in the passenger fender liner above the wheel, and were able to re-attach a vacuum line to the original canister, but that doesn't do anything with the check valve, which no one can even find. There are vacuum canisters you can buy, but it sounded like they might not be large enough (?).

Okay, if anyone is still with me, a question just out of curiosity (and back to issue #1, the heated vents): If the HVAC knob is in the Off position, is there still circulation through the heater core? Not that it would be practical to drive like this, but I was just wondering.

It is a bit irritating having to re-engineer the working-as-designed HVAC system of a van that has been in production for decades :a7:

So in summary, does this sound reasonable for my rig:

1) Fabricate and install larger vacuum canister and new check valve above passenger footwell; abandon OEM canister/check valve. OR... if/since the leak seems to be small, is there something else easier I could check first?

2) Install Max Air, then install The Cold Rush which is really what I want, but you have to put in the Max Air first.

(massively intimidated by doing any of this!) (if anyone knows of anyone really good/trustworthy - preferably a one- or two-person shop in N or NW Arizona, please let me know).

carringb 09-26-2014 11:53 AM

Re: Heater valve bypass to fix "heated dashboard vents"?
Viva it sounds like you do have a vacuum leak. Because it's affecting your EGR it probably
Upstream of your hvac. A vacuum leak going to the fuel canister can be large enough to affect other systems.

Viva 09-26-2014 02:51 PM

Re: Heater valve bypass to fix "heated dashboard vents"?

Originally Posted by carringb
Viva it sounds like you do have a vacuum leak. Because it's affecting your EGR it probably
Upstream of your hvac. A vacuum leak going to the fuel canister can be large enough to affect other systems.

That does sound right. Pardon my complete ignorance on this, but does this mean the leak (presuming there is only one) is not in the impossible-to-get-to canister and check valve? Where would I look for the lines that are upstream of the HVAC? I'm not very familiar with the inner workings of the V-10 and stuff under the hood.

And am I right in presuming that this is likely the EGR/defrost-on-loaded-acceleration issue cause, but that the "heated vents" are separate and "by properly operating Ford design" and so they will require the Max Air and Cold Rush fixes from Diesel Site if I want to change their behavior?


PS: I just looked at the receipt from the place that worked on the EGR last spring. I was thinking that was related to the 0455 code (I have been getting both 0401 and 0455, but I thought the 0401 was an evap leak (?), but here is what their notes say on the work order:

Check computer for codes. Code P0401 EGR insuff. flow. Checked and replaced DFPE Sensor. Possible other cause of code but diagnose flowed to DFPE Switch.

This doesn't mean a whole lot to me as I'm unfamiliar with the system in general, but it did not fix the codes (or at least I still get them, both 0455 and 0401).

carringb 09-26-2014 02:58 PM

Re: Heater valve bypass to fix "heated dashboard vents"?
I wouldn't say a faulty HVAC vacuum component would not affect the other systems. I just thing it's less likely that a vacuum leak under hood or under van. But... anything is possible. It certainly would warrant some additional diagnostics IMO.

But you are correct that a vacuum leak would not affect air vent temperature, only air vent selection.

I've had two major vacuum leaks. One was the rear blend door ruptured. This affect the front A/C eventually, but anything else. I also had a major leak from my fuel tank, because the tank pressure sensor was not installed properly by the body shop. Only found it when I had my fuel pump replaced preventatively. This caused some various codes, and also created some bad intermittent pinging when pulling the trailer up steep grades. Probably would not have found it if I weren't worried about fuel pump life (in fact, I thought the pinging was probably due to low fuel pressure.... and maybe it was but either way its fine now!)

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