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willysmjeeps.com :: View topic - M38 Temp Gauge
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M38 Temp Gauge

 
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Boze
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Joined: Aug 13, 2008
Posts: 92
Location: Bloomfield Twp., Michigan

PostPosted: Fri May 15, 2020 2:58 pm    Post subject: M38 Temp Gauge Reply with quote

Bought a new temp sending unit from a MV dealer at the convention last year and finally got around to installing it. It seems to read double the actual temperature. After running it for about 5 minutes it was reading about 235 but the top hose wasn't that hot nor was the radiator - just warm. Is there a ying and yang to senders and gauges? There is plenty of clean coolant, no leaks and water pump and thermostat work fine. Flow has always been good. Just wondering if the sender and gauge need to be the right ones before I start tearing down the cooling system.

Thanks for input.

Boze
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kenperkins
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Joined: Apr 14, 2005
Posts: 243
Location: Livermore Ca.

PostPosted: Fri May 15, 2020 3:16 pm    Post subject: Reply with quote

does it match your sender ?
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Boze
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Joined: Aug 13, 2008
Posts: 92
Location: Bloomfield Twp., Michigan

PostPosted: Fri May 15, 2020 4:39 pm    Post subject: Reply with quote

Don’t know, but it should. Both were sold to me by MV dealers who said they were for M38s and have Douglass connectors. Why wouldn’t they? How many senders can there be?
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OKCM38CDN
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Joined: Feb 17, 2012
Posts: 425
Location: Del City, OK

PostPosted: Fri May 15, 2020 7:54 pm    Post subject: Reply with quote

Early gauges required resistors to be in line with the gauges... could you have an early gauge?
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1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
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wesk
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Joined: Apr 04, 2005
Posts: 15107
Location: Wisconsin

PostPosted: Sat May 16, 2020 12:45 am    Post subject: Reply with quote

Let's skip the guessing and get right down to the meat. What are the part numbers of the your temp Gauge and Temp Sender? Is your M38 completely stock and still 24 Volt? Have you checked the resistance range of your sender and compared that to TB 9-2300-228-20 Troubleshooting Military Vehicle Instruments?

We can see you did not research the part numbers before you bought the new items so now is a good time to explain how to answer your question:
Quote:
Both were sold to me by MV dealers who said they were for M38s and have Douglass connectors. Why wouldn’t they? How many senders can there be?


To make the answer as simple as possible I'll stick with manufacturer's part numbers:

Gauges:
AC# 1512244 Gage, Water temperature, with external resistor Used thru MC17855

SW# 505A Gage, Water temperature, with external resistor Used thru MC17855

AC# 1512422 Gage, Water temperature, with internal resistor Used after MC17855

Senders:
AC# 1512245 Sender, Water Temp (1951 ORD 9)

AC# 1512423 Sender, Water temp (1956 ORD 9)

Quote:
Is there a ying and yang to senders and gauges?

Can you tell us what this phrase actually means?

Quote:
Just wondering if the sender and gauge need to be the right ones before I start tearing down the cooling system.

Yes they usually do.

One very simple check you can make is checking your water temp with another gauging system. An infrared heat sensor or a simple mechanical temp gauge available at any auto store. I keep one hanging on the wall in my shop with an assortment of adapter fittings.



Finally, if gauge/sender mismatch is not the issue then the usual culprit is wiring and specifically bad grounds. The military temp, oil press and fuel quantity gauges reguire a separate ground for the gauges internal needle drive mechanism wiring as well as the needed ground at the sender. The restos we do all have way to much paint on them causing many grounding problems.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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Boze
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Joined: Aug 13, 2008
Posts: 92
Location: Bloomfield Twp., Michigan

PostPosted: Sun May 17, 2020 8:21 am    Post subject: Reply with quote

Thanks, Wes. I've got some work to do. My rig is 24volt. I have an early M38 but replaced the entire instrument cluster because the original was shot. I think I don't have a separate ground so that may be it. I'll start by checking the coolant temp with a thermometer and make sure I have good throughput of the coolant. Then I'll add the ground wire. Then I'll check the sender and the gauge for manufacturer and number.

Where would I find a correct resistor if that is what I need? An MV dealer or an auto parts store?

Thanks again. A letter on this site tends to be very fruitful.

Boze
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wesk
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Joined: Apr 04, 2005
Posts: 15107
Location: Wisconsin

PostPosted: Sun May 17, 2020 7:38 pm    Post subject: Reply with quote

I wouldn't suggest a vendor for something you may not even need yet.

The important thing I had hoped for was that you would show an interest in properly researching your needed data in the applicable manuals. In your case TM 9-8012, ORD 9 SNL G-740 and TB 9-2300-228-20. All 3 are free PDF downloads here on our web site.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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bluewatersailor
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Joined: Nov 19, 2010
Posts: 106
Location: ITALY - TUSCANY

PostPosted: Tue May 19, 2020 2:51 am    Post subject: Reply with quote

Wes, I may be having just another senior moment, but I am unable to find TB 9-2300-228-20 in this site's download section. Suggestions please.
Bluewatersailor
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wesk
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Joined: Apr 04, 2005
Posts: 15107
Location: Wisconsin

PostPosted: Tue May 19, 2020 7:44 am    Post subject: Reply with quote

I suppose you could say it is a wee bit buried.

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