Horn Adjustment Question...

OKCM38CDN · Post by **OKCM38CDN** » Sun Aug 01, 2021 12:44 pm

I rebuilt my horn for my M-38A1 and inadvertently moved the adjustment. The horn sounded like a squeak more than a horn. I took it back apart and opened the gap some and have not tested it yet.

Has anyone measured the adjustment point on the horn to see what it was.

I have opened mine to 0.020".

Internals after rebuild / cleaning.

RonD2 · Post by **RonD2** » Sun Aug 01, 2021 1:25 pm

Hi Hal,
Do you have a copy of TM9-1825B, Autolite Electrical Equipment?

The section on horns (page 366) calls out two 24vdc horns, the HX-4001UT and the HX-4002UT. The adjustment for both is .043

Good luck!

RonD2 · Post by **RonD2** » Wed Aug 18, 2021 8:39 pm

Hi Hal,
Did you get it sounding manly?

4x4M38 · Post by **4x4M38** » Thu Aug 19, 2021 5:59 am

Manly?

I think the civvy horns sound like the roadrunner in the cartoon!
Maybe where Plymouth got the idea!!

How do the 24 volters sound?

OKCM38CDN · Post by **OKCM38CDN** » Thu Aug 19, 2021 7:18 am

My horn is not a Autolite, and so the manuals do not apply.

I have to adjust to just close or tighter for it to even sound, It moves but badly, the center shaft seems to have a bunch of corrosion in the portion that moves and so I have to take it apart and see if I can get some lubricant in there to make it move better.

The horn is a Sparks - Worthington dated 4-53 ord no 7728341

So I will keep working on it...

Post by **wesk** » Thu Aug 19, 2021 9:31 am

We discussed this about 12 years ago on G503 board. http://www.willysmjeeps.com/v2/modules. ... ic&p=11414

Perhaps if it won't sound manly you may have a M211 backup warning buzzer!

Here is a little Sparks-Withington (Sparton) history: https://www.encyclopedia.com/books/poli ... orporation

Here's a little more info on gap adjusting a Sparton Horn. https://forums.g503.com/viewtopic.php?f ... ea18a6319b

Here's a lot of Patent Info: https://patents.google.com/patent/US4361952A/en

OKCM38CDN · Post by **OKCM38CDN** » Thu Aug 19, 2021 11:25 am

Thanks Wes, as far as I know the horn is correct for the M-38A1 The Ord No 7728341 is the correct horn per the SNL.

I can get it to semi work so I guess I will try cleaning the contacts. When I opened it up I could not get the plunger on the relay to work, lots of corrosion in there and have not figured out how to get it apart without doing damage to it...

Will keep working on it in stages, as do not want to damage it, is actually in good shape...

Post by **wesk** » Thu Aug 19, 2021 12:29 pm

Correct only because the Sparton PN was included in the ORD# and FSN in later years in the M38 ORD 9. The M38A1 ORD 9 Lists that ORD# 7728341 but under the manufacturer's column the only numbers listed are Autolite HX4001UT and WO# 800906. By 1952 when M38A1 production started the Factory had already switched to Autolite HX4004UT (the squared back horn). When you go forward to 1959's TM 9-2320-208-20P they add even more useable numbers IE FSN 2540-735-1412, & for later substitution FSN 2590-349-3650 which takes us back to late M38 WO# 8380883 (the later flat back horn).