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CMH - keep it or block it?

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Old 01-11-2019, 02:54 AM
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CMH - keep it or block it?

Hello everyone,

Long time since I've been on here, but I need some advice. I just had my 22R out of my '86 truck, did a full gasket job, HD timing replacement, waterpump, oil pump, painted everything, did all sorts of stuff. I did an EGR delete a while ago when I installed my 32/36 with manual choke, but never thought it was worth doing the intake water block kit. I thought the wire from the bottom of the intake was a sensor, something for the electric choke.

Now I realize the CMH is actually a heater, used for cold starts.

I can't find any good information about this thing. What I would like to do, is to bypass the truck control of this unit and add a spring switch to the dashboard. Like in my diesel construction equipment with the engine heater, when you're starting, hold the switch, let go and it turns off.

Is this worth it? I installed a freeze plug block heater, so I doubt its really necessary, but going above and beyond is kind of my thing, and I like the idea of this heater so i don't want to buy the LCE block plate and get rid of it if I can make it work in my favor.

Let me know if anyone has any experience with this, or if I just block it off, remove the fuse and trace back and delete the wires.

Thanks!

Old 01-11-2019, 08:58 AM
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Here is how the Cold Mixture Heater works:




The factory system uses coolant temperature input and a charging input (meaning the engine is running) to help determine when the emissions computer should turn the heater on.

Basically when you swap to a Weber 32/36, all of the factory methodology goes out the window and many driveability / emissions systems get "deleted" as they are not compatible with the minimalist approach of the Weber.

I don't think it would be worth it to wire a switch to the dash as you would be guessing when to turn it on and when to turn it off, with probably little benefit with the Weber and block heater.

If you are still unsure, you can leave it as is, unplugged, and experiment to see if it makes a difference with your setup. You can also just leave the heater in place and just not use it.

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