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22manybugs
Samba Member
Joined: March 30, 2006
Posts: 419
Location: Yorba Linda, Calif
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 Posted: Thu Jul 23, 2015 10:41 pm Post subject: VDO mechanical pressure gauge is worthless |
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I just wanted to warn people about problems with a VDO mechanical pressure gauge, the small one that you connect directly to the engine.
I was having some questionable results from my electrical pressure gauge, so I thought the mechanical gauge would be a good way to double-check the electrical gauge by connecting off the same spot as the electrical gauge with a T. Didn't realize it at first, but this one consistently shows about 20 PSI lower than the electrical gauge, and it would show 0 PSI up to about 2000 RPM when the engine was hot. Sheesh, that just added to my problems! I finally figured the engine would have seized if it really was 0 PSI up to 2000 RPM, so the mech gauge must be the problem and I pulled the gauge apart to look at it.
I found out the linkage connecting the pressure tube to the mechanical gearing is sloppy on both sides. The pressure tube has to move quite a bit before the needle reacts. That's why it's always about 20 PSI too low.
I always thought VDO name was great, so I thought I must have just gotten a bad gauge. I bought another one, and it's the exact same problem!
I've sent a message to VDO technical help, I'll post on here if I get any response. I would say to just stay away from these gauges.
_________________
Lon
1969 Karmann Ghia convertible
1971 Westfalia camper |
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22manybugs
Samba Member
Joined: March 30, 2006
Posts: 419
Location: Yorba Linda, Calif
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| Posted: Fri Jul 24, 2015 9:16 pm Post subject: |
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VDO responded right away, they said they checked ones in stock and those work properly. They are going to send me a new one. That's encouraging that they responded promptly. I'll post how the new one works.
_________________
Lon
1969 Karmann Ghia convertible
1971 Westfalia camper |
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22manybugs
Samba Member
Joined: March 30, 2006
Posts: 419
Location: Yorba Linda, Calif
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| Posted: Thu Jul 14, 2016 11:00 pm Post subject: Re: VDO mechanical pressure gauge is worthless |
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I forgot to post the follow up:
I got a new gauge direct from VDO, plugged it in, and it was only reading 10 PSI low. I guess that's considered good to VDO 
I took the new one apart and the links were not quite as sloppy, but still sloppy enough that I'm getting a 10 PSI error in the reading.
So out of three mechanical gauges, the "best" one was only 10 PSI off. What a joke. I won't be buying mechanical gauges again from VDO.
_________________
Lon
1969 Karmann Ghia convertible
1971 Westfalia camper |
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