WUR Resistance value

[fritzgator]

Chasing down CIS troubles. It's an 83 SC. what should my resistance value be? just pulled the WUR out and while the PB blaster is soaking, I thought i'd ask. My meter reading across two pins was infinity, after test gauges tell me it wasn't "warming" at all, just a steady 30 psi reading cold or warm. Thanks to boyt911SC and paulprosche for there help w/ my previous troubleshooting posts. It's good to know, what info the bentley doesn't have, you guys do.

[Porsche_monkey]

WUR refurbishing???

WUR ohms question

FWIW: My Cheap AAR Fix (long)

The 'search feature' is your friend.

[T77911S]

infinate is bad
20-35 is good
there is a switch of some kind in yours, it will not hurt to open it and take a look.

[Gunter]

PB blaster soaking? What's soaking?
I would open the WUR carefully and find out why there is infinity. Wires burned or disconnected? Should have about ~30 OHMS with a digital, not analog meter.
I would also test the wiring with 12V to see if the bi-metal heats up.
Clean the inside, lube the pin with a dab of grease so it stays straight when you reassemble.
Bosch WUR number for '82= 0 438 140 090.

[fritzgator]

Thanks,gentleman. Yeah, i kept getting a blank page when i searched for WUR resistance values, so i went straight to the top on this one.Sorry.
Gunter, just the nuts on the body. Very dirty and didn't free up w screwdriver. Work smarter,not harder.

[boyt911sc]

Fritz,

Since your WUR is 0-438-140-090, you'll be needing 31 ohms resistance (heater) to get back the original spec. Search for 'Mysterytrain' post about his AAR heater rebuild. The bimetal and heating resistance are quite similar for these components. HTH.

Tony

[Paulporsche]

Fritz,

If it's possible, you can help me w/ a little WUR problem I'm working on right now. I would like to know some things about your bimetal strip once it is working:

1. What is the bend in the arm? Can you trace it or photo it from the side dead on to show how much bend there is?

2. If you do get a resistance reading, what is it?

3. How much does the arm actually bend while 12v is applied to it?

4. How long does it take to go from ccp to highest wcp and @ what temp?

1 and 3 are probably most important to me. If you can do it , that would be a great help. If it's too much trouble, that's OK. Thanks.\

Tony,

Do you have a chart for various WURs? I have just opened up a 045 and it is stamped 26 ohms.

Do you know, will a higher resistance arm take longer to heat up and bend than a lower resistance one?

[fritzgator]

Paul, unfortunately my heating element is toast, so all i can help with is metal strip bend.Hard for my camera to focus so tightly, but it's pretty much dead flat. since i got an infinity reading across my heat element i decided to try and disassemble it after checking out Mysterytrains AAR element rebuild. You could see that there are 3 ribbon strips running under the surface. what you can't see is the veerry fine wire between the ribbons. my dremel found them...and shredded them before i could pull it back.

don't know that i like the idea of exposed wiring in a fuel rich enviorment. Finding a replacement element seems next to impossible. looks like a$250 rebuilt WUR is the alternative.

[Paulporsche]

Thanks for doing that, Fritz. I have 2 elements here, both of which are also dead flat. I wonder if that means anything, since the section drawing we always see has a distinct bend.

I'm currently trying to open (always that last frozen nut!) another one to examine the arm.

The 2 I've examined have have the resistance stamped on them. The 045 is 26 ohms and an Audi one I have has 23. I'm about to see if they measure up, heat up, and bend.

[boyt911sc]

Originally Posted by Paulporsche

Fritz,

If it's possible, you can help me w/ a little WUR problem I'm working on right now. I would like to know some things about your bimetal strip once it is working:

1. What is the bend in the arm? Can you trace it or photo it from the side dead on to show how much bend there is?

2. If you do get a resistance reading, what is it?

3. How much does the arm actually bend while 12v is applied to it?

4. How long does it take to go from ccp to highest wcp and @ what temp?

1 and 3 are probably most important to me. If you can do it , that would be a great help. If it's too much trouble, that's OK. Thanks.\

Tony,

Do you have a chart for various WURs? I have just opened up a 045 and it is stamped 26 ohms.

Do you know, will a higher resistance arm take longer to heat up and bend than a lower resistance one?

Paul,

I don't have chart or table for these WUR's. But I do have some data taken from the assorted WUR's in my collection. Most of the heaters wrapped on the bi-metallic strips have stamped on them. The -045 spare I have has 24 ohms stamped on it but reads 24.6 ohms when measured.

The bi-metallic strips bend because of heat due to differential coefficient of expansion. The amount of heat that is generated by the heater (resistance) is related to the degree of deflection. But the higher resistance heater will have a greater degree of deflection because of the total heat generated.

Remember it is not which heats up faster but but which generates higher heat value. So a higher heater resistance will have greater deflection. More resistance more heat generated. BTW, I'm not an electrical engineer so correct me if my statements are flawed.

Tony

[Porsche_monkey]

That's backwards. Power = (voltage)^2/resistance.

Current increases as resistance decreases, so lower resistance means more current and therefore more heat. Maximum heat is a short circuit, not an open circuit.

(I stayed at Holiday Inn last night,)

[Paulporsche]

I just opened up a 1980 WUR. It has those contact points attached to the heater. Stamped on the heater is 14ohm 26 ohm. When measured I got 9 ohm. When powered up, it heated and I could see the arm bend. Does anyone know the function of that contact component?

One of my 045 (79) WURs is stamped 26 ohm. I measured 25.9 ohm. Strangely, that one heated up but I don't think I could see any bend in the arm.

P_M,

I never knew a monkey could be so smart!

BTW I have just fitted that known working top portion of the '80 unit to a vacuum bottom of a 045 and will fit to the engine today. I'll post my findings on my WUR thread.

[Porsche_monkey]

Educated beyond my intelligence. Way beyond.

[Paulporsche]

Jim Williams just informed me that the reason for the contact points is so the bar heats up slower @ temps below 60F than above. Looks like that's the reason for the 2 resistance figs. Funny, when I tested the element I got 9 ohms.