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post #1 of (permalink) Old 01-09-2002, 02:29 PM
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Jeep Heater Motor Ground

My jeep CJ7 blazer heater motor upgrade doesn't work. But when I touch a ground to the case of the motor it works. Where is it supposed to be grounded? It's way too cold right now to not have heat!!

Jon - 1985 CJ7, 258, 77k, T-176, Dana 300, 1" body lift, 31's, wrangler tub, yellow!
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post #2 of (permalink) Old 01-09-2002, 02:36 PM
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Re: Jeep Heater Motor Ground

Jon, I grounded mine directly from the battery. I had two additional pigtails off the main (-) cable. One went inside the cab to a common grounding block the other to the fan motor casing. I drilled a small hole in the casing as there is plenty of clearance inside and used a self tapping screw through a wire connector. Then sealed the connection with clear all-weather goo.

'85 CJ7 in pieces..
Daily driver - 2000 FLSTC
post #3 of (permalink) Old 01-09-2002, 02:37 PM
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Re: Jeep Heater Motor Ground

I ran a ground wire from motor case to good ground.My heater has been working fine.

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post #4 of (permalink) Old 01-09-2002, 03:12 PM
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Re: Jeep Heater Motor Ground

The case of the motor is grounded:
a. From the motor case to
b. The back plane of the heaterbox to
c. The mounting studs to
d. The firewall.

I cut a 5/16" bolt and welded it to the motor case and ran a grounding strip to the firewall from that lug. So far in 6 years it's never failed.

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post #5 of (permalink) Old 01-09-2002, 04:14 PM
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Re: Jeep Heater Motor Ground

I thought of doing the self tapping screw thing so now I will try it. Just the reply's I was looking for, thanks guys. The motor goes on and off if I mess with the heater box so I am pretty sure a good ground to the firewall and I will be set...

Jon - 1985 CJ7, 258, 77k, T-176, Dana 300, 1" body lift, 31's, wrangler tub, yellow!
post #6 of (permalink) Old 01-10-2002, 06:32 PM
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Re: Jeep Heater Motor Ground

A question for you guys on this topic:

I just got done modifying my stock, placebo heater (69CJ)to accomodate a larger motor/fan from a 70's Wagoneer. Much more output, but...........

The original fan was a 3-wire job. The wagoneer fan is a 2-wire job, which means I need a switch with built in resistance if I want varied speed control.

So, my question(s):

Where can I grab a switch like this; and,
would it be a good idea to run a relay on this circuit?



post #7 of (permalink) Old 01-10-2002, 08:41 PM
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Re: Jeep Heater Motor Ground

Assuming the waggie's two wire job is a hot and a ground you could use a CJ's three speed switch and it's associated dual coil resistor which resides in the CJ's plenum to keep it cool.
The switch and the resistor will do the speed control to a single wire to the fan motor ... in theory ... [img]/wwwthreads_images/icons/smile.gif[/img]

Oh, and I grounded my heater motor by running a 10 ga black coated wire from the bottom most heater housing through firewall stud on the outside of the firewall (including bare metal circle and star washer) to a ground buss (to batt) I'd installed (ala CJdave) on top of my fender well.

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