Testo 550 repairs/parts ??

[acguytx]

Ok so i have been using the 550 for a few yrs now and its working fine but recently the Highside knob on the manifold leaks refer when i use it but stops if i fiddle with it.

I imagine i need to replace/rebuild the valves?? so do they have a replacement or is it as simple as taking them apart and replacing some O-rings?

anybody who has done this walk me through the procedure, thanks

oh and i need yet another hanger hook, arghh..i hope they get a different type soon..

i have my DC 1250s to use in the short term so not worried! :P

[acguytx]

?? anybody?

[qwerty hvac]

I have been using mine with no issues. Call true tech tools or Testo and see what they say.


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[jim bergmann]

Ok so i have been using the 550 for a few yrs now and its working fine but recently the Highside knob on the manifold leaks refer when i use it but stops if i fiddle with it.

I imagine i need to replace/rebuild the valves?? so do they have a replacement or is it as simple as taking them apart and replacing some O-rings?

anybody who has done this walk me through the procedure, thanks

oh and i need yet another hanger hook, arghh..i hope they get a different type soon..

i have my DC 1250s to use in the short term so not worried! :P

The valves have to be torqued to very specific requirements and the instrument leak checked after it is repaired. It will need to be returned to Testo for service.

Testo, Inc.
40 White Lake Road
Sparta, NJ 07871
Attn: Service

Make sure to include a phone number and return address on a separate card.

[acguytx]

The valves have to be torqued to very specific requirements and the instrument leak checked after it is repaired. It will need to be returned to Testo for service.

Testo, Inc.
40 White Lake Road
Sparta, NJ 07871



Attn: Service

Make sure to include a phone number and return address on a separate card.

how long was the warrnaty on this product and and estimate of shipping and repairs?

might not be worth fixing if the cost is more then half of what i paid for it??

[jim bergmann]

2 years from date of purchase. Not sure of the cost. You will have to ask them.

[acguytx]

2 years from date of purchase. Not sure of the cost. You will have to ask them.

do you have a number to their service department? thanks

[mark beiser]

The valves have to be torqued to very specific requirements and the instrument leak checked after it is repaired.

They always say that, but most of us are smart enough to figure out how to tighten a valve enough to keep it from leaking, without stripping the thread in the aluminum block.

[Gunslinger]

just went thru the same repair...It cost $56.00 including return shipping.

[2141]

I literally mailed mine out a few hours ago because my high side knob was leaking. It started leaking for no apparent reason, wasn't bumped or even turned. Mine are less than a year old.

[itsiceman]

So at the cost of a new manifold you could get yours repaired

[Brent Ridley]

oh and i need yet another hanger hook, arghh..i hope they get a different type soon...

I'm in my third hook. This is the only issue I've had with the 550's. I was looking at the 557's the other day and they come with a heavier duty hook. It may be because the 557's weigh more but I can only hope they wise up and start using those on the 550's.

[jim bergmann]

Testo Inc. 800-227-0729

[Qualitair]

Testo 550 leaking thru knob ?? Piece of cake!
Option 1: send it to Testo as recommended.
Option 2:
a. remove the retaining clip under the plastic knob.
b. Pull out the plastic knob, (should be easy.
c. Un-screw the brass nut around knob shaft using a 14 mm socket, (a deep one).
d. pull out entire knob when all treads are disengaged.
e. you'll see a small piston at the bottom of the knob assembly, it has 2 o-rings and a plastic seat. usually the o-ring gets defective.
f. replace both o-rings. I used silicone o-ring 2mm width by 6mm ID. I used the silicone because of the range of temperature, -60*F to 450*F. be careful not to scratch anything or to damage the new o-rings.I lubricated them with ref. mineral oil before, then after before re-inserting the piston-knob assembly.
g. Re-insert inside the testo, just be careful when you tight the brass nut, be sure the seat is not tight against the orifice at the bottom of the cylinder where you insert it.
h. As far torque for the nut, your tightening a brass nut inside an aluminum manifold, so if you're using too much performance enhancing drugs, ask somebody else to do it.
I tested mine with 300 PSI of nitro and also liquid R410, so far so good but hasn't been tested extensively.
I guess I'll find out soon. I do not recommend to do this yourself since Testo recommend to send it for repair and they are much smarter than i am.
By the way, I used part # 5233T49 from McMaster-Carr, comes in a pack of 50 for cheap.
Also, I love my testo 550 !

[PMARS2345]

I called Testo a couple of days ago for a new hook, apparently there is a beefier replacement.

[emptech]

I know this is an old thread, but I'd like to add my experience.

My unit is about three years old, probably out of warranty. I usually use it with 134a and 410a. One day with 134a, I noticed a quick squirt from under the high side knob, wonder what was going on. Today I was using it on a 410a system, compressor wasn't even running, not only did I get a squirt of gas and refrigerant oil through the valve stem, I found oil inside the 550 itself.

Having been an instrument tech for many years, I wasn't afraid to take the unit apart and see what failed. On the valve stem, it was the O rings. Replaced, but also found it was leaking from under one of the brass nuts inside. The high side pressure transducer was leaking, the brass nut was only finger tight, same with the low pressure sensor. I don't know why it waited this long to fail, but sure looks like it wasn't properly assembled at the factory. That doesn't explain the O rings on the valve stem going bad though, unless it didn't like some of the refrigerant oils.

I cleaned the oil up inside the unit, until I purchase the 2mm x 6mm O ring from McMaster, I used some O rings purchased locally, slightly thicker, but they work.

Next thing, get the unit all cleaned up inside and put it back together, hope it works! I'll try to report back with the results.

Jim H.

Testo 550 leaking thru knob ?? Piece of cake!
Option 1: send it to Testo as recommended.
Option 2:
a. remove the retaining clip under the plastic knob.
b. Pull out the plastic knob, (should be easy.
c. Un-screw the brass nut around knob shaft using a 14 mm socket, (a deep one).
d. pull out entire knob when all treads are disengaged.
e. you'll see a small piston at the bottom of the knob assembly, it has 2 o-rings and a plastic seat. usually the o-ring gets defective.
f. replace both o-rings. I used silicone o-ring 2mm width by 6mm ID. I used the silicone because of the range of temperature, -60*F to 450*F. be careful not to scratch anything or to damage the new o-rings.I lubricated them with ref. mineral oil before, then after before re-inserting the piston-knob assembly.
g. Re-insert inside the testo, just be careful when you tight the brass nut, be sure the seat is not tight against the orifice at the bottom of the cylinder where you insert it.
h. As far torque for the nut, your tightening a brass nut inside an aluminum manifold, so if you're using too much performance enhancing drugs, ask somebody else to do it.
I tested mine with 300 PSI of nitro and also liquid R410, so far so good but hasn't been tested extensively.
I guess I'll find out soon. I do not recommend to do this yourself since Testo recommend to send it for repair and they are much smarter than i am.
By the way, I used part # 5233T49 from McMaster-Carr, comes in a pack of 50 for cheap.
Also, I love my testo 550 !

[emptech]

Not that it's important, but my 550 is about a year and a half old and has had two failures. Until the proper O rings arrived from McMaster-Carr, I used some oversized O rings. It's not easy finding metric O rings. I used some that were over-sized, they worked fine, UNTIL, the new O rings arrived and I started taking the valve stems out and one would not come out. The oversized O ring sealed the stem but wouldn't allow it to be removed, I pulled so hard, broke the thin part of the brass shaft. I ended up plunging in with a milling machine, destroying the valve stem. I ordered a new set of valve stems, but in the meantime, took a couple hours and fabricated a new valve stem. With the new 2mm x 6mm O rings, perfect fit.

Again lesson learned, don't use an oversized O ring.

Jim

[Greg Lykens]

I've had some issues with leaks and sensors. I like the gauges, as I have the 557, but sending them back are a pain. Therefore I now have two gauges.

I don't think the micron reading on the vacuum is very accurate. And the accuracy of the gauges , too me, seems suspect in weather below 20 degrees

[emptech]

I believe there is a lack of quality control. As mentioned, at least one of my transducers leaked, leaving oil all over the insides. The nut was only finger tight. In less than a year and a half one of my valves leaked very badly, sprayed 410a refrigerant all over the face of the instrument. I replaced the O rings with silicon O rings, and now have a bag of spares, for a lot less than a spare valve set.

I read, not exactly sure where, although the instrument will measure vacuum, it is no replacement for a micron gage. Accuracy, the specifications show +/- .5% of full scale. Full scale is 870 psi according to the manual, therefore, accuracy is +/- 4.25 pounds. There is no mention of linearity. Most people do not understand accuracy, they read a number on a digital instrument and believe that is the true measurement. The numbers are relative, what does a few pounds mean, what if it was a mechanical gage, you couldn't read down to that detail anyway.

Thermisters are inconsistent and are unlinear, unlike a thermocouple, but they are cheap and don't require a sophisticated measuring device, but again, how about linearity and is the thermister calibrated at several points within it's range?

What I like about this instrument is the bluetooth, I can remotely read the instrument, unfortunately the range isn't very long, if I have a compressor on a rooftop, and I'm in the walk-in downstairs, it usually doesn't work. I can capture the data into a spreadsheet and save it for the record, I like that.

Conclusion, I think it's a good product, but if you own one, count on having these problems. Testo wanted me to send the unit back for repair. I had to ask them if parts were available. I ordered a spare valve set to find that it was back-ordered, it was quicker to repair the instrument myself. I was an instrument tech for over 30 years, so I'm not afraid to take the lid off.

Jim H.

[Gunslinger]

The valves have to be torqued to very specific requirements and the instrument leak checked after it is repaired. It will need to be returned to Testo for service.

Testo, Inc.
40 White Lake Road
Sparta, NJ 07871
Attn: Service

Make sure to include a phone number and return address on a separate card.

The torque is 8 Newton’s. They say to use blue thread locker on the threads. There is a Youtube on this repair.