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hiatus · 06-14-2021, 11:05 AM

Just had the Demco AF1 installed on our 2020 Jeep Grand Cherokee Trailhawk. I've had an intermittent issue where the ESC (Electronic Stability Control) off warning appears. It seems to happen when Jeep is idling for more than 10 minutes or when the Auto Stop/Start feature is turned off.

Has anyone had a similar issue with their Jeep GC after the AF1 unit was installed?

Bikinjim · 06-15-2021, 05:12 AM

The AFO really doesn’t interact much with the electronic systems of the vehicle. It’s primarily a mechanical system powered by the coach braking air. It taps into the vacuum brake booster and has a 12v electrical connection to provide power to the notification light and to energize the opening of the breakaway air reservoir when the breakaway switch key is removed. I don’t see how either of these two interactions could affect the stability control if the installation of the AFO was performed properly. It’s possible that something was inadvertently disturbed during the AFO installation that could lead the anomalous stability control system such as loosening an electrical ground or disturbing a wheel speed sensor. It seems more likely to me that it’s a coincidental issue rather than a cause and effect from the AFO. I had a 2015 Cherokee that developed stability control system errors shortly after I bought it which durned out to be a defective wheel speed sensor that was repaired by the dealer under warranty. I have had issues with my AFO that resulted in the check engine light illuminating that turned out to be caused by defective AFO check valves which resulted in a continuous vacuum leak. You can check for a similar vacuum leak by listening for air flow from the AFO control box air exhaust port. That exhaust port will make a very noticeable air leak sound when the check valve closest to the control box fails open. Demco is very good with technical support so don’t hesitate to call them for advice.

jkorn · 06-15-2021, 06:38 PM

Don’t see how they could be related. Completely different systems on your Jeep. Air Force only ties into the vacuum system. Jeff

hiatus · 06-16-2021, 05:17 AM

I took my Jeep Trailhawk to another branch of the company that installed the system yesterday. This location had a tech who had installed many systems. He said all looked fine initially, but when he pulled apart each connection he found that the previous tech had used teflon tape around each of the plastic fittings for the check valves and for the vacuum connection to the AFO unit. He said that is not to be done and could cause a vacuum leak. Evidently the plastic valves and connectors are designed to bite into the vacuum hose rubber and to create a good seal. The teflon tape prevents this. He also found that the AFO brake piston was installed so that it was continually partially depressing the brake pedal. The tech removed all of the teflon tape, reconnected everything and also put zip ties around the vacuum hoses at each connection point. He also readjusted the AFO brake piston attached to the brake pedal which evidently was lightly applying the brakes and affecting performance. So far, I have not had any more ESC off errors messages.

I had also talked to the Demco tech rep who said this type of error is almost always related to a vacuum leak issue. The initial install tech had failed to add the check valve closest to the AFO unit and this caused the ESC off message to appear immediately. On the second visit they corrected this, but then the intermittent error message started.

Bikinjim · 06-16-2021, 05:36 AM

Quote:

Originally Posted by hiatus

I took my Jeep Trailhawk to another branch of the company that installed the system yesterday. This location had a tech who had installed many systems. He said all looked fine initially, but when he pulled apart each connection he found that the previous tech had used teflon tape around each of the plastic fittings for the check valves and for the vacuum connection to the AFO unit. He said that is not to be done and could cause a vacuum leak. Evidently the plastic valves and connectors are designed to bite into the vacuum hose rubber and to create a good seal. The teflon tape prevents this. He also found that the AFO brake piston was installed so that it was continually partially depressing the brake pedal. The tech removed all of the teflon tape, reconnected everything and also put zip ties around the vacuum hoses at each connection point. He also readjusted the AFO brake piston attached to the brake pedal which evidently was lightly applying the brakes and affecting performance. So far, I have not had any more ESC off errors messages.

I had also talked to the Demco tech rep who said this type of error is almost always related to a vacuum leak issue. The initial install tech had failed to add the check valve closest to the AFO unit and this caused the ESC off message to appear immediately. On the second visit they corrected this, but then the intermittent error message started.

Thanks for updating the cause for your problem. As I noted, I too received error indications on my Equinox (2 separate events) from vacuum leaks although my cause in both cases were from failed open check valves which required replacement (flapper disk was pulled through the seat). Demco was good to provide new replacement check valves at no cost. You really had a substandard initial install, glad the second tech resolved the remaining deficiencies. In hindsight I found I could tell when a vacuum leak was developing as the brake pedal would not be soft when applying the brake to start the car after a period of non use (like overnight) which indicates the brake booster had lost its vacuum. When there are no vacuum leaks the pedal will stay soft for long periods of non use time (like many days).