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Old 04-06-2021, 05:50 AM   #1
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Join Date: Apr 2021
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Firewall Vacuum Pump E3HT-2A451-BA

The following is related to a firewall mounted vacuum pump or generator which apparently actuates the heater / AC controls for the dash.
I looked at all the comments surrounding this component. Discussion was very old and didn't address a couple of simple questions...
Mine makes a noise about every 15 seconds, lasting approximately 1 second. The noise sounds like a stepper motor advancing (I understand it is not a stepper, simply offering a similar noise as an example) . Does it all the time with the engine running.

1. Does the noise sound appropriate / similar to what you folks see?
2. Does yours cycle this often??

3. Do you think I have a problem or is this normal?

Thanks all-
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Old 04-07-2021, 11:54 PM   #2
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You are most likely experiencing a VACUUM LEAK. When a vacuum operated system is intact, the vacuum pump will run for a few seconds during startup of the main engine. And, you have, just like regular cars/trucks etc. vacuum storage containers here and there, in the front of your coach. Those storage containers, some about the size of a soft ball, Tomato juice can etc., are there to store vacuum.

A good buddy just went through all of the same things you're experiencing. He found his vacuum canisters in good shape but, there was one cracked vacuum hose and a bad heater control valve. He replace all that and, his pump now runs for a short time when starting the coach, then it's done. He did have to remove much of the dash etc. to get at all those parts but, it was worth it to make things work correctly.
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Old 04-08-2021, 04:33 AM   #3
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Scott, Thanks very much for the information and your time in responding. The guidance supports the direction I was preparing to go on this. Dash work is such “fun”...
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