[200q20v] 3 pin vs. 4 pin multifunction temp sender?

[C1J1Miller at aol.com]

Apparently the newer version (3 terminal) can fail as well... per Scott 
Mockry's site:
"It has 2 other functions in addition to being the sending unit for the 
coolant temperature gauge. It is appropriately called the
     "Multi-Function" sending unit or Multi-Function Temperature sensor. Most 
repair shops call them the "Multi-Mal-Function"
     sensor, as they fail quite often and are not cheap to replace.

     This sending unit can have 3 or 4 terminal connections, the original 
sensor had 4 terminals and used +12V on terminal 3/+,
     the later replacement sensors used 3 terminals and are made by Behr. The 
original 4 terminal sensor was made by VDO and
     is fairly complicated inside, and has a ceramic hybrid circuit board 
with several active and passive electronic components.
     Some wholesale parts houses still have some of the VDO 4 terminal 
multifunction sensors available. 

     Fuse #12 supplies +12V to the Multi-Function Temperature sensor on the 
original 4 terminal sensors, so check your fuses.
     This fuse #12 also supplies +12V to the back up lights and to the 
speedometer sending unit in the transmission.

     The later 3 terminal version eliminated the requirement for +12V and is 
mechanical in operation, as it uses a thermal
     expanding pellet and 2 mechanical micro-switches for the 2 overheat 
functions, and a regular Negative Temperature
     Coefficient (NTC) resistive element for the coolant temperature gauge 
operation. A NTC resistive element, has a decreasing
     resistance with increasing temperature. 

     Unfortunately, the 3 terminal model fails after 2-3 years, and can fail 
giving a false overheat warning condition. "

Mine's (3 terminal) been fine for 4+ years, 80k+ miles (great, it's going to 
fail on the way home tonight...)...
Chris



In a message dated Tue, 2 Jan 2001  8:36:51 AM Eastern Standard Time, Bernie 
Benz <b.m.benz at prodigy.net> writes:

<< Reliability is the only issue.

B

> From: Brett Dikeman <brett at pdikeman.ne.mediaone.net>
> Date: Tue, 2 Jan 2001 00:35:20 -0500
> To: Bernie Benz <b.m.benz at prodigy.net>, Steve Bednarski
> <stevebednarski at mindspring.com>
> Subject: Re: [200q20v] 3 pin vs. 4 pin multifunction temp sender?
> 
> At 9:01 PM -0800 12/21/00, Bernie Benz wrote:
>> Yes, by all means!  I've never had a "new" 3 pin sensor from my local AW
>> fail.  Don't accept 4 pins, even if they agree to break one off.
> 
> 
> There is no functional difference between the two.  Either is
> acceptable for use.
> 
> B
> 
> 
> 
> -- 
> ----
> Brett Dikeman    Systems Engineer
> ProAct Technologies Corporation  914-872-8043
> (formerly CFN[formerly iClick, Inc])  914-872-8100(fax)
> 120 Bloomingdale Rd.   http://www.proacttechnologies.com
> White Plains, NY 10605
> PGP Fingerprint: 06C2 5D5B D2B4 7626  BB24 2BBC 9E4A C8B3
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