I have 2002 EB Expedition with EATC. When I am using the A/C either on auto or manual the A/C will blow from the dash and then sometimes go through the dash vents. I can get it to blow through the vents again if I change rpms. Any ideas? I searched but could not really find anything.

Thanks

Mike

 

I was troubleshooting it this morning and found the vacumn leak, it is a vacumn hose that is located top of the firewall on battery side, then diasappears under the dash, anyone know where that vacumn line connects to? Where to start tearing my dash apart to repair?

Thanks

Mike

 

My guess would be to your temp control unit

 

I am about to start troubleshooting the same thing, and as it started, figured it was a vacuum leak right off the bat.

Did you find the problem?

Mine is a 2003 Navigator with the automatic controls, dual A/C.

I was hoping it was the line into a vacuum canister or something like that. Taking the dash apart will not be very fun. But, I think I can get to the back of the control panel relatively easily...

Hopefully there is a common fix - so if you have fixed yours, let us know. Now, on to further "searching"...

 

Follow up -

Problem was (at least so far) in the 4 adapters that take the hard vacuum lines to their associated parts:

- Vacuum canister (rectangular behind the battery)
- The two check valve set up where it takes vacuum from the engine and sends it to the above canister and to the a/c control vacuum line which goes through the "firewall" (though we can't call it that, right...)

They were really soft and the black wiped right off...

Changed them using vacuum lines - no cost...

 

Post update - never mind on the above. I drove it over the weekend, and it ran o.k. Did not take it on the interstate though. Wife said it acted up today on the interstate...

 

Have you tested the one-way vacuum check valve for leakage?

 

My 03 is having the same exact problem.
Craig

 

Didn't have the time to write the other day that I checked the two check valves (on this year, they have two of them - one is a Y-check valve, the other is the basic single check valve) that make up the overall assembly that distributes the vacuum to the canister and to the line that feeds the dash controller. However, I checked them for functionality - did they suck vacuum in only one direction - if that is what you mean.

I also checked for leakage on the canister itself.

Both checked out o.k. Although - I tested with my older vacuum tester that has developed a slight leak, so I ended up using the old faithful sucking and using your tongue as the gauge...

I did just buy a better vacuum tester so I guess I will recheck.

The whole assy is only $15 at the dealer, so if anyone finds a problem, it is best to get the hose assy with the fittings, hard lines and the two check valves. Not a bad deal. I did not get it because it was an order and I needed to use the ride, so I just replaced the vacuum lines that adust their size with regular vacuum lines...

 

Hey guys,

I had the same problem on my E-350 for work. It was a crack in the Plenum. It was about $350 dollars to have it fixed. I know that it is a different vehicle, but I assume the problem would have the same cause.

Bill

 

Do you mean your intake manifold plenum? Like the upper or lower plenum? If so, which one or did they replace both.

Maybe I'll T a vacuum gauge in the line and monitor the engine vacuum while running down the road and see what is going on there when it happens.

 

It defaults to this when vacuum is lost to operate the doors.

The wife's 02 expo had the same issues. Used a hand vacuum pump also used for bleeding brakes, to pull a vacuum on the box behind the battery and the smaller line going into the firewall. That one would not hold a vacuum. So I inspected the line and could not find anything so now I'm thinking it's under the dash. Jump ahead 1 week, I realized it was going to be a major pain to to pull the dash apart and went back to the line under the hood again for another closer inspection. Sure enough, 3 very small cracks I missed the first time. This hose is formed with a bend. I straightened out line to find them. Quick fix, cut 2" of the line, worked the rubber boot off with a jewler's screw driver to break the glue and slipped it back on the hose. Back to factory specs and the wife is happy again.