Cooling fan speeds for 84 without resistor.

[mekanism]

I'm having some cooling issues where it only gets hot after driving a while and then driving at slower speeds and idling the van starts to get hot, (needle at 75%). I turn on the heater and A/C switch to get it to cool back down before the red light comes on, which has never happened. I have read about changing the resistor behind the headlight but pre 86 models have the built in fan resistor.

My fan does come on at the high speed when the temp goes up then promptly shuts off and the tempts go back up. If I leave the A/C fan switch on the van never overheats (my A/C is not functioning). If I leave the heater on the van never overheats. It seems like the low fan speed isnt working, I never hear a fan come on unless I turn the A/C switch on.

1) Is the problem a bad fan relay (the built in one)?
2) Is the temp switch on the radiator bad?
3) Is my radiator plugged up?

Sorry for another boring cooling issue question but there doesnt seem to be much info on the earlier models when it comes to these specific issues.

[DubNuts]

.
My guess is the Thermo Sensor switch that's in the radiator..

Easily tested by removing your lower grill and pulling the radiator fan connector off of the switch.

Take a paperclip and bend it U shaped hold the bent clip firmly with a pair of needle nose plies and jump 2 of the 3 connectors.

Forget which one is the inbound Hot Lead, and the other two go to the Fan Low and High speed.

So when you jump the leads your hear the Low speed, and the other is the High speed Fan.. If not then it's something in or your Fan itself..

If the Fan Ran on Low and High when jumped it's most likely the Thermo Sender mounted in the radiator you pulled the connector off.

The connectors could also just be making a bad or corroded contact.
.

[mekanism]

[Terry Kay]

You can try a new fan switch.

When's the last time a new radiator was installed?

Very typical for the temp switch not reading the coolant temps due to the tubes being plugged up at the bottom of the original radiator.
Pretty common happening.

Save the flushing till you get the new
radiator-- put a U pipe in the end of the radiator hoses & flush it out then

Turning on your heaters to cool it down is the dead giveaway.
Your radiator is all done.
_________________
T.K.

[mekanism]

[Terry Kay]

How often has the cooling system been flushed?
Every two years for the last 30 years?
I had an 89 Carat with 68,000 miles & the radiator was junk.
Plugged up on the bottom 3 rows of tubes prohibiting the switch from operating.
Trust me, the mileage means nothing.
Proper & timely maintenance sure means everything.
Your heaters on are acting as mini radiators cooling the engine down.
Changing that switch on a plugged up radiator won't cure the operating temperature .
And if your having a hard time digesting this, go buy an IR temp gun, let the coolant get hot and hit the bottom 3- 4 rows of tubes, close to that switch.
When you find out that it isn't even warm, you'll understand why, and then you'll replace it.

I thought I'd save you some time& money.
_________________
T.K.

[mekanism]

Damn, I already bought the switch, but I'm pretty tapped out on this thing for a while. I will just have to drive with the heater on until I can afford a new rad. Thanks for the help!

[Terry Kay]

Well, your one step ahead of yourself.
It's a real good idea to start with a new switch with a new radiator anyway.

You weren't thinking of using the 30 year old switch --were you?
_________________
T.K.

[mekanism]

[Terry Kay]

The front hoses are a real good idea, along with the switch, plus get new antifreeze in it.
_________________
T.K.

[crazyvwvanman]

If I were you I would put in the new switch and see how it goes after that. Since you said high speed was coming on and low speed wasn't clearly the switch should be changed. While you have the old one out shine a light into the hole and see how much blockage you see in there, if any.

With the upper grill removed you should be able to see the year of the radiator molded into the black plastic side tank, on the passenger side. If it is original to your year it should have and 83 or 84 molded inside of a small circle. One that old should be changed, generally.

Mark

[Terry Kay]

Perhaps you could let me in on how Harry Houdini is going to get a visual on the tube blockage in those tubes above & below & to the back side, and for the length of the same coolant tubes in that radiator.
X-Ray perhaps?
In this instance, and in any Vanagon horizontal tubed sealed radiator, the only way is to verify uniform temperature, or take it apart and take a look when you get both side tanks removed.
The latter inspection being a bit more difficult & time consuming.
Radiator might leak when you get the tanks back on.
_________________
T.K.

[crazyvwvanman]

Most people would just use their eyes and see what they can see. Some visual information is better than none.

Mark

[Terry Kay]

If most folks were the man in blue with a red cape I would have to agree.

I can't imagine how mortal man could see if the tubes were plugged at either ends of the multiple stack of horizontal tubes.

Can you leap tall buildings in a single bound too?


An IR gun would be much more efficiant.
_________________
T.K.

[crazyvwvanman]

He said his radiator cools ok when air is moving over it. He said his rad fan isn't working at low speed from the temp switch but when he turns on the A/C the fan runs and keeps temps ok. Since his tests and symptoms point to a bad fan temp switch he bought a new one. Now it is time to put it in and save the engine from some unneeded stress, not to mention the occupants.


While he is changing it he has a chance to look at the age of the radiator marked on the side. He can also look into the empty switch hole and see how things look in there. No capes or xray vision needed for either.
Mark

[Terry Kay]

"And the Survey Sez";

If he's turning on the heater's to lower the engines operating temperature the problem is;

****The radiator is plugged and not cooling the fluid.****

There--that was pretty simple.

Compounded by the fact that he's manually turning on the AC, to get the radiator fan on high--in conjunction with, and including the heater fan motors being on.

This smells like a all done radiator to me.
_________________
T.K.

[crazyvwvanman]

Lets see, the rad fan is part of the cooling system. The cooling system keeps the engine cool. His rad fan isn't working because his temp switch isn't working. Surprise, when his van isn't moving enough for much air to flow through the radiator his engine isn't staying cool. Maybe he should fix the rad fan and see if that helps keep his engine cool. That is why cars have rad fans after all.

Mark

[Terry Kay]

<<I'm having some cooling issues where it only gets hot after driving a while and then driving at slower speeds and idling the van starts to get hot, (needle at 75%). I turn on the heater and A/C switch to get it to cool back down before the red light comes on>>

Radiator.
_________________
T.K.

[Terry Kay]

<< If I leave the A/C fan switch on the van never overheats (my A/C is not functioning). If I leave the heater on the van never overheats.>>

More indications of the radiator being plugged , by adding the heater fans into the mix.
Been there, seen it , & done it.

Let him replace the switch & lets see what happens.
_________________
T.K.

[Farf]