Wow, I guess I didn't know that it wansn't supposed to do that.
My fan also comes on only at one speed. T-man's email wanders a bit and I
just get confused after a while. I must be impatient. What should I do
about this, if anything? Inga, the 87 Syncro GL.
Thanks,
Steven

>
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
>Of TinkerMan
>Sent: Monday, August 12, 2002 9:07 AM
>To: vanagon@GERRY.VANAGON.COM
>Subject: # Importance of pressure and temp monitoring (long)
>
>Hi Volks!
>
>Recently, I had the radiator fan speed reduction
>resistor go down on me. As a result, the radiator fan
>would turn on only at high speed when the coolant was
>really hot.
>I didn't pay attention in the beginning, thinking it
>was the hot weather...
>Well, in the end, this resulted in a blown A/C dryer
>pressure relief (requiring replacement of dryer and
>refrigerant, $$$$$) as well as a blown coolant hose.
>
>The A/C pressure relief blew because my A/C serviceman
>hacked a replacement pressure switch which somehow
>didn't protect the A/C system from high pressure.
>Why high pressure? because the radiator fan didn't
>cool the radiator most of the time, until coolant was
>really hot (the resistor burned in the common circuit
>that controls both the low speed as well as the A/C
>minimal speed activated when A/C is on). In the end,
>that was enough to cause exessively high pressures in
>the A/C to blow the pressure relief valve.
>
>And why did the collant hose blow? because the higher
>engine coolant temperature resulted in higher
>pressure. Of course the coolant pressure cap should
>have relieved it (and might have if it reached 15psi),
>but old hoses always are a weaker point in the
>system...
>Still have to check the coolant pressure release cap
>for 15psi, although it was lately testy OK. Darn,
>can't rely on those dealer mechanics (BTDT...).
>
>Also, there have been many posts regarding engine oil
>pressure monitoring. Many say that catastrophic
>failures can be avoided if unordinary pressures (both
>low and high) are noticed. Even the builtin so-called
>"dynamic pressure monitoring system" isn't enough and
>won't detect exessive pressure instances at all (e.g.
>when pressure relief valve is stuck).
>
>Which leads me to the obvious conclusion that all
>pressures of important systems must be monitored and
>warned against exessive pressures: Oil, coolant, A/C,
>etc.
>I know this sounds paranoid but from my experience
>noticing a simple failure promptly and taking action
>can save huge sum$ and grief resulting from
>catastrophic failures which could have been avoided.
>
>SSSOOO...here's what I'm looking for:
>1. Good point to check coolant pressure. Methinks that
>a convenient spot would be the "T" where the left head
>connects via hose (VW 025-121-058M) to the coolant
>manifold. A "T" could be added for the sensor without
>changing the system. Any better spot, e.g. the coolant
>distributor, outputs to the rear heater which I don't
>have? I don't want to drill a hole in the coolant
>expansion tank like someone suggested...(I've had
>enough trouble with that one!...).
>
>2. Good spot to measure oil pressure: Many have
>recommended the 0.3 bar pressure switch location with
>extension hose and dual sender or "T" with standard
>sender: Is this BEFORE or AFTER the oil filter?
>Anyway, I don't like this extra hose dangling around
>there (even tied to something) but maybe there's no
>better option. Any better ideas?
>And I want to connect to it THREE senders: the
>original 0.3bar, an analog sender and a high pressure
>alert (in case of overpressure). Anyone know what
>would be the maximal recommended oil pressure? What's
>the spec of the oil pressure relief  valve?
>
>3. Good spot to measure A/C pressure: wouldn't be easy
>(no place to tap in). Maybe use the integral pressure
>switches with a buzzer, but have to make sure the
>sender is working OK first.
>
>******
>
>After we finished with the pressure issue, now comes
>the temp issue...
>
>1. Coolant temp is monitored in the dashbord, but is
>quite unreliable: I had a double failure where my
>coolant leaked overnight, and my coolant level sensor
>(in the expansion tank) was cracked and allowed
>coolant to seep up to the connector, so when I drove
>happily away my dashboard meter showed nothing (temp
>sender was measuring air temp in the thermostat...)
>and the coolant level sensor indicated all was well
>(because the wire connnector above was wet, fooling
>the coolant level "relay" to think there was enough
>coolant...:-(
>Well, since then, I've added a seperate sensor right
>on the #3 head (hottest?) near the coolant exit
>(there's a threaded standoff there) and it works
>great. I even have an alarm circuit that can be set to
>a certain threshold, both for coolant temp as well as
>head temp (near the coolant exit). I thought about
>even adding another sensor at the exhaust port
>(another threaded standoff there) but I'm not sure if
>my sensor will stand those high temps.
>Anyone have a wide range thermoprobe to measure what
>temps can be expected there?
>I'm just wondering where is the best place to sense a
>catastrophic failure (coolant or oil loss) resulting
>in overheating. This is more relevant in aircooled
>engines, but can be used to the benefit of W.C. too.
>Anyone know what's the best place to measure temp on
>A.C.? Maybe there's a similar location on WC since the
>engines are based on the AC design?
>
>2. Measuring oil temp: I'm aware of the various
>methods of measuring this (drilling sump plate and
>installing sender, but prefer not to drill, or temp
>sender dipstick which is claimed not to be accurate).
>All in all, I think I've got it covered with my other
>temp sensors.
>
>3. I need a source for LOW COST but reliable senders
>for the above. VDO might be good, but are defenitely
>not cheap. Also, ideas for tapping into the various
>systems to be monitored.
>
>4. The most important issue: with all those sensors
>and senders, I need to display them all...
>I don't have room (or desire) for an airplane cockpit
>in the dash, so I'd like to have a single meter there
>switchable to the various senders. The problem is that
>usually each sender has it's own characteristics and
>matching gauge. I'll have to scale them down for a
>single compact meter, hoping they all are referencde
>to ground...
>
>Well, that's my rambling. If anyone has implemented
>such monitoring stuff, I'd be glad to hear practical
>experiences and recommendations...
>
>
>=====
>Cheers, T-man.
>
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