EATC in my '00 Monty

[Mesozoic]

I normally ride a motorcycle to work, but after installing a high performance 5.0L engine in my '00 Mountaineer, coupled with the fact that the monsoons are building up along with high ambient heat, I've been driving the truck to work for the last several weeks. Recently, as soon as I'm at a good 75 mph cruise on the freeway the air stops blowing out of the front vents, but the rear vents work fine. At some point, the air starts blowing again out of the front vents. The truck is equipped with the EATC (Electronic Automatic Temperature Control?) system, where you set your temperature and it automatically adjusts various things to achieve that. Of course, I don't use it in that manner - I just set it to Max A/C and adjust the fan speed.

On inspection of the system, I noticed that the power connector to the blower motor was burned and disintegrating. I assumed that this was probably caused by the age of the motor and the added drag from dried out bearings or whatever is causing it to draw more current. So I replaced the entire blower motor assembly, which was a VDO model made in China with a new Four Seasons part that is made in Canada. I also upgraded the connectors on the harness and blower motor side to Deutsch DTP parts using machined contacts to handle high current reliably. I had to use MIL spec crimpers to achieve that, interestingly. The previous installation of the VDO motor did not use a gasket, but had siliconed the interface, so I had to clean all that out and made myself a new gasket out of some nice rubber.

The blower motor replacement yielded an improvement in blower output when it works, but the intermittent air delivery from the front vents is still present. So I went to Autozone and grabbed a new Duralast JA1652 blower motor resistor module. I swapped this in and was surprised to see the original BMR in place. I took it apart and didn't see the slightest of anything burned, so not sure the BMR needs to be replaced, but I did it anyway because the foam seal was shot on the original part. Still have intermittent blower output on the front vents.

At this stage, I went through all the vacuum connections thoroughly. I don't see anything wrong with the vacuum lines in the engine compartment and this is confirmed by the fact that if I remove one of the lines from the vacuum canister in the passenger fenderwell, you can hear the vacuum being released because it holds it without issue and doesn't leak. This leaves the EATC unit itself and that's where I've stopped because I'm not very familiar with its operation and whether it controls vacuum directly via internal servos or what.

Curious if anyone else has experienced anything like this with their 2nd Gen Ex or Monty.

 

[Turdle]

Vacuum leak somewhere in the system, or, could be the vacuum reservoir is filled with condensated water.

This thread should help

How to: - 2nd Gen NO AC ( or heat) FROM VENTS!!! A "How to" what to look for thread

Here is what to look for if you have a 95-01 with cold ac, and hot heat, but it only blows from the defrost vent. IF YOU HAVE COLD AND / OR WARM AIR BLOWING FROM DEFROST DUCT ONLY THIS THREAD IS FOR YOU!!! I will immediately delete all ac cooling questions without answer-let's stay on track...

www.explorerforum.com

 

[Mesozoic]

I just had the reservoir out and it felt pretty dry and empty to me. I reckon I've melted one or more of the vacuum tubes (grey and black) that go back into the firewall on the passenger side. I have headers and I remember trying to route those tubes away from them when reassembling the truck during the engine upgrade.

It's definitely a bit of a vacuum leak because the reservoir runs out of vacuum after prolonged load, but is readily reobtained after coasting or letting off a bit. If it's in the dash there will be tears, but if it's in the engine compartment that's at least something I can deal with.

 

[410Fortune]

Okay first off maybe do a self test of the eatc and see if any codes

The default position for air coming from your vents is the defrost
It requires vacuum from the engine bay to change from defrost to any of the other positions

You can test this at the vacuum manifold at the rear of the eatc with a simple
Vacuum pump, this will show that things are working in the dash and the issue is the vacuum feed from the engine bay (every time I do this testing I find the dash works great and the issue always seems to be in the vacuum feed)
However I have also replaced a couple of eatc head units over the years for similar vacuum control issues
Yes the vacuum manifold is directly on the back of the eatc/head unit just like the manual temp controllers

Some
Cams may have trouble producing enough intake vacuum to get things switching, an electric vacuum pump can be added to assist with this. Diesel superdities use an electric vacuum pump for just this purpose as diesel engines do not produce intake vacuum

 

[Mesozoic]

Thanks for the suggestion on diagnosis. I've run codes on the EATC and it doesn't report any issues - handy little feature that unit has! The new engine has been running fine with the AC on until just a few days ago. It still blows cold air through the front vents, but only when the vacuum is high - when the engine is loaded, it depletes the vacuum reserves in the orb and then switches to the defrost output. I think the tubing has finally cooked on the passenger side, but I will confirm this later today when I rack the truck on the lift and pull the wheel and fender cover down. It's definitely a vacuum leak, albeit a very small one. I found some heat shielding I can use on the vacuum lines if I do find them to be culprit.

Incidentally, an old '60-70s Buick Riviera tried to run me at the light twice yesterday evening while I was out running an errand. Despite the vacuum leak, the Mountaineer handily walked away from this gentleman's hot rod, much to his dismay. LOL

 

[Mesozoic]

UPDATE
So the vacuum leak had become very pronounced after some city driving today, so I stopped at my friend's shop this evening. We smoked the engine and the HVAC system and hooked up the vacuum gauge. When I first measured vacuum at idle when the engine was new months ago, I was seeing between 11-12 inHg. The readings now were at around 8-9 inHg. So definitely something leaking.

Didn't take long for us to find the vacuum source connection at front of the intake plenum as being the culprit. The rubber had dilapidated to the point of failure, so we fabricated something short term for testing. Sure enough, the vacuum was up to around 10-11 inHg. Then we smoked the engine and didn't find any leaks. We smoked the HVAC system and found nothing. The orb is good as is the EATC connector. Then we smoked the power brake booster. Traces of smoke inside the cabin - so we bypassed the brake booster and measured vacuum again. 11-12 inHg without the booster in the circuit.

I'm going to pull the booster vacuum port in the morning to see if it's holding vacuum overnight, but if it's not, that's the next issue to resolve, I guess.

 

[Mesozoic]

I managed to resolve the problem. The issue was 3-fold and I threw in another mod just for good measure:

• I replaced the power brake booster. It was definitely a vacuum leak by itself.
• I repaired a T-fitting for vacuum at the front of the intake plenum.
• The grey vacuum tube that connects to the heater control valve was totally cooked to the point of crumbling in a few sections upon touch. I cut it down until plastic with good integrity was found and then replaced it with some Festo 4.0x0.75mm tubing and fittings. I wrapped all of the new and old good line with some heat shielding and put it all back into service.
• The PCV valve was the original stock EV-192 part. I had a low mileage PCV from a '93 Mustang GT hanging around, so I swapped that in instead. The body of the valve is slightly taller than the EV-192, but the opening at the bottom is smaller. My thought was that the EV-192 was worn out and the spring was allowing excessive vapor into the engine.

AC runs great in 110F heat, while stopped at a light or not and it's always blowing out the front vents now.

 

[410Fortune]

Good job!

 

[Mesozoic]

Good job!

Thank ye, thank ye - always feels good to resolve an issue like that!

 

[Mesozoic]

The Duralast JA1652 BMR assembly died after 1 week's use. The failure mode manifested with the main blower motor running full tilt as soon as the ignition key was turned on. I suppose that's a better failure mode than no blower motor at all, but regardless, I don't think the Duralast part is very durable. I swapped in the stock BMR and everything is working fine.