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Topic: AC/Fan not blowing air thru instrument panel -Dorman Vacuum Tank Unit is the fix (Read 799 times) previous topic - next topic

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Re: AC/Fan not blowing air through instrument panel (Dorman Vacuum Tank Unit)

Reply #25 – June 28, 2019, 01:32:32 am

The inlet, the small tube you can blow into, should go to a vacuum source on the intake manifold, the large tube powers the HVAC system. Connect the new line to both ends of the old line, cutting out and bypassing the old.
Looks like you are almost done.

Larry

Re: AC/Fan not blowing air through instrument panel

Reply #26 – June 28, 2019, 01:41:12 am

Harold & Greg--

RE: "I hate rodents" Despite the fact that Pixie & Dixie were portrayed as simply mischievous, I agree with the famous Mr. Jinks, "I hates meeces to pieces!"

Klaus--

I learned about Fresh Cab Rodent Repellent at Ladeze a few years ago, & highly recommend it--non-toxic & smells nice, too. I'd found a few droppings in the storage bays, but fortunately nothing like the damage so many have reported here, & no critter condo like you discovered. I keep a bag in every storage bay & wired one under the hood; when I put the baby away for her winter hibernation in the barn I put abut four inside the living space (one between the beds in the back, one in the kitchen area, one midway in the lounge area, & one by the dog house), & I've never found another dropping anywhere. Though I'd been fortunate to never suffer a critter attack on the tractor, I keep a bag wired under the hood of the tractor now, too.

Good luck with this project.

Lynne

Re: AC/Fan not blowing air through instrument panel

Reply #27 – June 28, 2019, 11:58:50 am

Unfortunately, no success.

The new line from the intake manifold is creating a well perceptible vacuum and connected to the smaller (right) nozzle of the canister, the other (left) nozzle is - with the help of a small piece of the new line as a "fitting" - connected to the old line that goes up into the dashboard. With some effort it is also possible to blow manually into this line that goes up into the dashboard.

However, the AC is as before only blowing through the defrost and floor outlets. This is very frustrating. All for nothing - and the existing lines forever destroyed. It is especially frustrating as I found the old line being broken directly behind the firewall when I removed the grommet there. I really thought I found the reason for the malfunctioning.

I tried to connect the lines the other way around to the canister; that does not make a difference.

When I disconnect the line that goes up into the dashboard from the left nozzle and connect a short piece of the new line there and have the engine running, I can neither feel a vacuum nor any air coming out. Is it supposed to be like this, or should I feel something here? What should happen on that side of the canister when the engine is running - blowing or sucking?

Is there anything else that I can try?

Klaus

Re: AC/Fan not blowing air through instrument panel

Reply #28 – June 28, 2019, 01:50:08 pm

Quote from: Larry W - June 28, 2019, 01:32:32 am

The inlet, the small tube you can blow into, should go to a vacuum source on the intake manifold, the large tube powers the HVAC system.

It works! Cold air is blowing through the dashboard outlets into my face!

I did once more what I had already done before and connected the hoses the other way around to the canister as I understood it from Larry. I was anyway wondering why I should connect the sucking hose to the nozzle that can be blown into. Strange is that it did not work when I did this before. Glorious is that it works now!

To make it clear to anybody who needs to do this in the future: When using the $10 "Dorman HELP! 47076 Vacuum Tank Unit" the sucking line coming from the intake manifold in the engine compartment has to be connected to the larger nozzle on the left side of the canister (see picture), and the line that goes inside the passenger compartment up into the dashboard has to be connected to the smaller nozzle on the right side of the canister (the one with the little hood on the side).

I'm quite relieved - and I'm wondering what to do with the saved $900. I think I definitely deserve some kind of reward, don't I?

And again - so much thanks to the community here. I would not have done this without you. I hope to see some of you on the road sometime.

Klaus

Re: AC/Fan not blowing air through instrument panel

Reply #29 – June 30, 2019, 04:38:04 pm

I have now pulled the new line - which I before had running through the window and the hood into the engine compartment - through the firewall. Another test of the system was again successful (I still can hardly believe to have fully working AC again). I'm basically ready to fix the canister and reattach the metal plate and the plastic cover in the passenger footwell (and go on to the next project).

One question remains. The new vacuum line fits very tight onto the larger left nozzle and kind of tight but not as tight onto the (cone-shaped) smaller right nozzle. Is that enough, or do I need to fix the lines tighter or permanently to the nozzles? In both places it would not be possible to use hose clamps - I would have to use glue. I'm actually quite confident that the (anyway slightly sticky) silicon hose will stay on the canister, but I thought it cannot harm to ask here.

If it is better to glue the silicon line to the plastic canister - what kind of glue do I need?

Klaus

Re: AC/Fan not blowing air through instrument panel

Reply #30 – July 01, 2019, 12:34:26 pm

Very interesting..... We just got home Saturday from a four-week trip and had this same issue crop up!
First, air has been coming thru floor vent even though vent control is in off position. Then later, when it was super windy, the air (AC and vent) would alternate between blowing thru the dash vents and the defroster, randomly back and forth.   Since it's a vacuum line issue, maybe the heavy wind gusts contributed to this happening? We were also in the high desert at altitude, along with the high winds when this was happening. At other times, air flows normally thru the selected position. Sounds like it's an expensive fix at a dealer, so will probably just see how it performs on the next outing!
   Daryl

Re: AC/Fan not blowing air through instrument panel

Reply #31 – July 01, 2019, 01:45:42 pm

Quote from: LazDazGuy - July 01, 2019, 12:34:26 pm

We just got home Saturday from a four-week trip and had this same issue crop up!

From my experience I can say that it is fairly easy to fix this yourself in maybe 2-3 hours. The best and almost perfect instructions are on the Lazy Dazy Companion website (The Lazy Daze Companion: Cab AC - Air Flow Cuts Off Under Acceleration). I had to read it several times directly at the rig before I felt confident to do this. It then went very well.

The parts cost around $25:

Dorman HELP! 47076 Vacuum Tank Unit ($10)
Amazon.com: Dorman HELP! 47076 Vacuum Tank Unit: Automotive

10 ft of 5/32" Vacuum Line ($10)
Amazon.com: Hiwowsport High Performance 10' Length High Temperature Silicone...

And 2 or 4 small hose clamps ($5). Additionally maybe some glue to fix the hoses to the canister. I would suggest to buy 10 ft and not just 5 ft of vacuum line - by doing that I could run the new line first through the door and the hood to the old line that leads to the intake manifold and make sure that I really fixed the damn thing.

Klaus

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Re: AC/Fan not blowing air thru instrument panel -Dorman Vacuum Tank Unit is the fix

Reply #32 – July 03, 2019, 02:52:28 pm

thanks, Klaus!
Thinking maybe I'll order the vacuum tank & hose so when/if I have the opportunity to tinker around in there, I'll be prepared. Probably best to attempt this while I'm visiting my parents' since my dad could likely help me out with his deeper skill set in this area under the hood!
Daryl

Re: AC/Fan not blowing air thru instrument panel -Dorman Vacuum Tank Unit is the fix

Reply #33 – July 03, 2019, 08:50:09 pm

Quote from: Klaus - June 28, 2019, 01:50:08 pm

To make it clear to anybody who needs to do this in the future: When using the $10 "Dorman HELP! 47076 Vacuum Tank Unit" the sucking line coming from the intake manifold in the engine compartment has to be connected to the larger nozzle on the left side of the canister (see picture), and the line that goes inside the passenger compartment up into the dashboard has to be connected to the smaller nozzle on the right side of the canister (the one with the little hood on the side).

Klaus

That bit of confusion is covered under #4
4) The reservoir has an inlet and outlet nozzles, but it's not marked which is which. The 5/32 hose (the one you just pulled through the firewall fits one of the nozzles, but it's not the right one. Cut a short piece from the 1/8 hose you cut off, stick it in the 5/32 hose and the other into the cannister. Just reverse that for the other nozzle.

Re: AC/Fan not blowing air thru instrument panel -Dorman Vacuum Tank Unit is the fix

Reply #34 – July 10, 2021, 02:52:37 pm

This two-year-old topic has been very helpful.

Last week we got Sidra out for some exercise. After a bit of driving I turned on the AC and what?, it only blows through the defrosters.

At home we found this topic (and others) and the Lazy Daze Companion article.

We then inspected the HVAC switches and vacuum hoses behind the dash. All were perfect. (The inspection was easy with the doghouse off; we had already been pulling it every day for a couple weeks to check a sticky trap set on top of the transmission housing.

) We then inspected the run of hose that can be seen under the hood. Perfect. We pulled the grommet through the firewall and, sure enough, the run of hose behind the fender had been bitten through.

We sourced 5/32 vacuum hose and a splice from O’Reilly Auto Parts and threaded the replacement vacuum line, fishing it through the firewall as described in the LD Companion article.

The hose and splice were ridiculously overpriced, but the total bill was around $15. Oh yeah, like Harold (Blueox25), we called Kearney Mesa Ford. They offered to fix it for $1800! Of course, they would replace every component in the system. Ridiculous.

This community is the best, and priceless.

Jim

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