Espar Diesel Heater New Impact Switch and Harness Replaces Original Push Button Version

All of our Navistar conventional school buses come with the Espar Hydronic 5 (E-Guardian) diesel coolant heater. The impact switches that came with the heaters are very sensitive and would pop when ever the bus went over rough roads.

We did a partial fix by using a hole saw and reaching in to the heater housing and resetting the switch. This was a hassle but necessary to keep them operating. Low and behold the engineers at Espar came out with a new impact switch and harness that does not cut out over rough road.

The part numbers for this unit are below. There are 3 harness options and just one impact switch. Impact switch number: 252800705050OZ . The harness that fits the Hydronic 5 we have is 25280070100200OZ. The International dealer can get you the parts or anyone who has dealer status for Espar.

A great advantage to getting Espar heaters is the software is free to download. Go to the Espar website to get the software. The heater comes on in cycles starting with the blower and fuel pump then the electrode to start the burner.

The fuel used is minimal about 1/2 a cup of diesel per hour. With anti idling laws around schools these heaters preheat the buses long enough to get the interior temperature up fast. They operate for 2 hours at a time during each cycle. The faster a diesel engine can warm up saves fuel due to less warm up time in the morning.

If you are interested in these heaters it's possible to install them after factory with a complete install kit. You just have to get a fuel feed from the tank and hook up the coolant plumbing and electrical. Our shop installed a Webasto heating system on an International conventional bus because it was parked out of town and we wanted more assurance that it was going to start in cold weather.

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Below is a video I did on setting the 7 day timer on an Espar

School Bus Heaters Article

I recently wrote an article for School Transportation News Magazine on Bus Heaters. The nice thing about researching for this subject is I learned a lot of new Mechanic information on the subject. Since our fleet has over 2 dozen bus heaters it was a topic of interest. Here is the link that will take you to the online digital version.
The pre-heating capabilities from these little heaters are phenomenal. There was a lot of positive feedback from fleet operators who saved fuel reduced engine wear and harmful emissions from cold diesel engine start ups. They don't cost a lot to run and can be adapted to bio-fuel and gasoline. The heat ratings go as high as 45,000 BTUs. One thing to point out especially with school buses is the safety and comfort of the kids these heaters provide. Imagine a bus breaking down on the highway during frigid temperatures. These heaters would be a huge asset to have around for that purpose along with defrosting the windows much quicker solving another common safety issue.


Here's a great video on an Espar coolant heater installed on a boat. The install here is the same for any kind of application.