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PDWA pressure failure switch

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1275midget Avatar
1275midget Mike's 73 Midget
over, hill and dale, USA   USA
Testing the brakes found brake fluid comming out of the brass assembly failure switch. A quick check of the MGE Tech Library points to need for PDWA o-ring replacement kit. OK with that, and makes sense. I thought since we are doing that, I would replace the plastic brake failure switch as well. Ordered it, tried to fit it up, and...no go. Thread stem too long, would not fit. Internet and additional MGE Tech Library search reveals this is not uncommon. I havn't solved the situation yet but here is what I have found, (and a couple photos (not my pics, 1st one from MGE tech archive, rest off the net) for explanation:

For 1973 Midget with brass PDWA assembly;

1. page 42 Moss catalog; switch for brass assembly 181-955
2. 181-955 arrives....does not fit. on the box is original part number; AAU2454
3. I go to Moss Europe site to look up AAU2454, it lists MGB/C master cyllinder dual line
system.
4. next, back to Moss Europe for 1275 late Midget search. It comes back with the pre-1275
assembly and switch style (as in the Moss US cataog).
5. I stay with Moss Europe site for a moment, remembering that some components stayed same
for longer with vehicles not for export (where did I read that?).
6. on Moss Europe page, for 1500cc dual line, there is the drawing of my PDWA and plactic
switch. ( #20 and #21). It also shows the pre-1275 unit.
7. this switch is AAU1700A.
8. Moss Europe lists AAU1700A for the brass and cast iron assembly
9. I go to LBCco search page and find it is the same as 542-115. And referenced to
Sprite/Midget, TR250/5/6
10. I go back to Moss catalog and type in 542-115. it is the listed switch for MG Midget
cast iron assembly.
11. to keep the obsession going I check MG Owners Club. If you want to find it there,
you have to by pass the brake or hydraulic pages and go to electrical. There it is, but listed as RTC826....not available. But AAU1700A is available, and listed for cast iron assembly.
12. I thought about checking Brown and Gammons, but changed my
mind, before it started to seem normal.
13. So as one final act, I typed in AAU1700A and googled it.
14. It led to a fellow who rebuilt his TR6 PDWA. He listed a cross reference number as
C8AZ-2B264-A sold directly by Ford Motor Company Parts site. It mentioned it was a
considerable cost savings.
15. So.......I found the Ford parts site. There it was at a considerable cost savings.

So my situation in summary: the part listed (Moss) does not fit. The part that shouldn't fit is listed on other sites as a probable fit. I tried to call Moss Tech, on hold through all of Golden Earrings Radar Love on the radio, couldn't wait any longer and hung up. So, I emailed them the situation to see if they had an idea on the issue. reply pending as of this writing.
I think I will order 542-115, or C8AZ-2B264-A (at a considerable cost savings), and see if it fits.

Has anyone been through this? What was the solution?

I usually don't drink coffee, but the lovely significant other brought me a Mocha Frappe, and its making me check all these web sites and relate this story. So unless someone has a better idea, I am going to order the part and see if it fits.



Edited 2 time(s). Last edit at 2012-08-06 08:41 PM by 1275midget.

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AmishIndy Avatar
AmishIndy Seth Jones
Glendale Heights, IL, USA   USA
1971 MG Midget MkIII "Guenevire"
2007 Mazda 3 "Porco Rosso"
Why bother? Its not like the metal shuttle is going to move when a failure finally does happen.



Seth Jones

1971 MG Midget

www.SpridgetGuru.com

1275midget Avatar
1275midget Mike's 73 Midget
over, hill and dale, USA   USA
Haa! Seth....kick me off that caffeine, sugar, and chocolate fueled charge, and bring the reality home.
You are probably right.

Moss Tech was kind enough to respond with a comparative photo of their stock, just moments ago.
Now I can decide.



Edited 1 time(s). Last edit at 2012-08-06 08:59 PM by 1275midget.

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GSlahor Gary Slahor
Baltimore, USA   USA
Before you decide, find out how the electrical portion of each switch operates.
I just ordered 2 of the 181-955 (thinking the first was a mistake) and not only do they not physically fit into the brass cross, but the switch does not function the same as the old one.

On the original unit, both terminals are connected together and they ground to the plunger when it is depressed.

On the 181-955 both terminals are initially connected, but when the plunger is depressed the connection is broken, and neither terminal gets grounded..... It will NOT function correctly.... even if it did fit.

Let us know if you find something that will both fit and function correctly. I still do not have a replacement for my old, failed switch.

dennisculpt Avatar
dennisculpt Dennis Lynn
Show Low, Arizona, USA   USA
1974 MG Midget MkIII "Urge"
I think I read on University Motor's website that they rebuild these units. Call John Twist, he has a "Tech Hour" between 1:00 and 2:00p.m. (E.S.T.) and I'm sure he will disclose the correct application. BTW, he is very pleasant to talk to, MG's are a part of his DNA.
http://universitymotorsltd.com/

subman Avatar
subman mark pettet
cape girardeau, mo, USA   USA
Do you really need this switch? The wires on mine are snapped off.

79midget Avatar
79midget Lee Fox
Saint Louis, Missouri, USA   USA
Yes, you need the switch and the PDWA to be working. It is the only safety feature of the braking system and, despite the trouble you're having find the right part, the system is very simple and reliable.

When they leak, it is always that one of the two o-rings have failed after 40 some years. The size of the o-rings has varied over the years and the Moss kit will have the ones you need in the assortment.

Also, it is important to keep the shuttle inside centered when you open up the system for bleeding or whatever. You can move it back with an awl or something so the annular groove is visible or make up this simple little tool:

It's a 3/8-24 bolt with a point ground onto the end that screws into the PDWA in place of the switch and holds the shuttle centered until you finish doing whatever it was you needed to do. Only needs to be hand snug.

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dennisculpt Avatar
dennisculpt Dennis Lynn
Show Low, Arizona, USA   USA
1974 MG Midget MkIII "Urge"
Excellent point, ...but if the PDWA is not centered, is this going to foil any attempt at bleeding all four wheels ?

Kerr Avatar
Kerr Platinum Member Norm Kerr
Ann Arbor, MI, USA   USA
Dennis, that is the point of Lee's tool. It holds it centered during brake bleeding.

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subman Avatar
subman mark pettet
cape girardeau, mo, USA   USA
I guess i should ask this in adifferent way. I have the switch in place but the plug attached to the wiring harness that plugsinto the pdwa is broken off the harness.

1275midget Avatar
1275midget Mike's 73 Midget
over, hill and dale, USA   USA
OK, this is the rest of the story:

I ordered C8AZ-2B264-A sold directly by Ford Motor Company Parts site. It is the same as Moss 141-725, but at less than 1/2 price. It fits.
141-725 is the pressure fail switch cross referenced to MGB in the catalog.

181-955 as listed in the catalog for 1275 Midgets brass PDWA did not fit my car, (which I assume the brass PDWA was original to the car).

Also, the o-ring repair kit for the PDWA stopped the fluid leak.

I emailed Moss tech to update them on my findings for their future reference.



Edited 2 time(s). Last edit at 2012-08-13 09:45 PM by 1275midget.


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141-725 C8AZ-2B264-A mgb tr6.jpg    5.4 KB
141-725  C8AZ-2B264-A  mgb tr6.jpg

GSlahor Gary Slahor
Baltimore, USA   USA
Can anyone confirm that the Ford switch works ELECTRICALLY the same as the MG part.

The two terminals need to be physically connected together, and ground to the plunger when it is depressed.

1275midget Avatar
1275midget Mike's 73 Midget
over, hill and dale, USA   USA
In reply to # 2145149 by GSlahor Can anyone confirm that the Ford switch works ELECTRICALLY the same as the MG part.

The two terminals need to be physically connected together, and ground to the plunger when it is depressed.

I will check that out as soon as I can, and report back.

Southern Man Avatar
Southern Man Skip C
Raleigh, NC, USA   USA
1972 MG MGB
I realize it's been 5 years since this thread went quiet, but it's exactly what I am trying to figure out.

Can anybody confirm the Ford C8AZ-2B264-A electrically operates (not just mechanically fits) as an early MGB PDWA works? N.B., this is electrically different and not compatible with the AAU2454 a.k.a. Moss 181-955.

Moss correctly lists the MGB date range for the AAU2454 as '76 onwards, whereas the component for earlier cars is No Longer Available. In the hopes of saving some of you guys from the run around I've been through, many other suppliers list the AAU2454 as '75 onwards. This is incorrect and it will NOT work on a '75. Ask me how I know...

Hence the quest....

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