A/C Cooling system temp gauge aux. fan

[Boots]

specs:

1988 4.0 Liter

NV3550

aftermarket A/C

Closed cooling system

 

First, I want to upgrade to the open cooling system but have some other issues that I need to figure out before I start taking stuff apart. It has a new water pump and thermostat already installed. So I need a new radiator and some sort of over flow bottle, Correct? What would you guys recommend for a radiator? What do I need to do to the heater control valve things? What will I need as far as hoses? Anything else I need to do?

 

Second, the aftermarket A/C wiring is horrible. There is a relay/fuse on the passenger side fender and a wire running across the top of the radiator support thing. I would like to redo most of this so that it is like factory, What all is involved? Should there be factory wiring already there?

 

Third, I'm assuming that the aux. fan was installed with the A/C because it only comes on with the A/C. I want it to come on like factory, with the A/C, at a certain temp, and I also want a switch in the cab. I'm going to need to get a HO thermostat housing and temp. switch, right? Is there any factory wiring already there?

 

Fourth, My temp gauge never seems to go past 155 degrees. It pegs while the engine is cranking and slowly goes up as the engine is warming up, but always sits right at 155 while running. Yesterday we took a long drive in heat atleast in the high 90's, and on top of that, I was driving up some really big hills in fourth gear at around 75mph. The coolant pressure bottle thing swelled up like a balloon and started forming a crack, but luckily didn't burst. The temp gauge didn't didn't even creep up a little. Am I being paranoid or is some thing wrong here? What should I check or replace?

 

I know that this is alot, but all help is greatly appreciated. :wrench:

 

Thanks

Chad

[flint54]

Chad,

 

I recommend this radiator: http://www.autopartswarehouse.com/detai ... F2671.html

 

I also recommend you find or buy one of these laser/IR temp guns: http://www.fluke.com/fluke/usen/electri ... ?PID=56096

(or equivalent), and measure actual temperatures at various points in the cooling system. I use as a reference temperature the thermostat housing where the

large hose connects. You are likely to find that your dash gauge is inaccurate, or screwed up. I don't think it should peg when cranking. How's life in Aptos? Used

to live there (Freedom Blvd) a great many years ago.

[ParadiseMJ]

If you convert to open cooling you'll need an HO radiator. Problem is most of the replacement or aftermarket 91+ do not have a bung for the temp switch in the radiator, so if you convert you will NEED a switch in the cab. Also, if you get an HO t-stat housing and try to put a SWITCH in it, you'll need a SWITCH, not a sensor that is in the HO models. You may get lucky and find a <94 corvette switch, but they don't make one for Jeeps.

 

There are 3 types of temp sensors/switches in a RENIX era Jeep.

1. Temp sender (back of head) for the gauge/light.

2. Temp switch (radiator), for the aux. e-fan to turn on at appx. 218-225

3. Coolant temp sensor, to feed info to your ECU for air/fuel mix.

 

The heater control valve is a completely different animal on an open system. First off it's plastic. Next off, they never even used it after 97...as in...straight hose through the heater core. My 90 XJ has no HCV, my 88 MJ does. It can be deleted with no adverse effect to the A/C system OR heater.

 

If you wire in a switch for the e-fan, all you need to do is splice in a switch/power wire to the existing fan relay. Just power off the fuse box and a wire to the fan relay (orange or yellow wire, you won't have both)

 

Can't tell you anything about the A/C, mine is factory and as yet is still R-12 (doesn't work). The XJ is R-134a, works great, but like I said it's factory.

 

The pressure bottle on your closed system needs to HOLD the pressure. Most guys overlook this thinking that it's just an "overflow" tank. Ususally the bottle itself is cracked or the cap is crap. In an open system, all you need is a generic overflow tank. It needs to remain about half full most of the time.

 

As far as hoses go, it depends how you're going to plumb it. If you are just going straight into and out of the heater core, you can use generic hose. If you're including the HCV you'll have to get a bit more creative with a combination of OEM and generic hoses.

 

Your temp SENDER (in the back of the head) or the temp gauge itself is shot. You can use a infrared temp gun to shoot at different parts of the motor, but concentrate on the back of the head and see how it stacks up to the gauge...if it's way off, replace the SENDER.

 

Let us know how it goes.

[HOrnbrod]

I agree with all of this post except this:

 

If you convert to open cooling you'll need an HO radiator. Problem is most of the replacement or aftermarket 91+ do not have a bung for the temp switch in the radiator, so if you convert you will NEED a switch in the cab.

 

I've gone through three HO radiators; one alum w. plastic side tanks, one alum w. aluminum side tanks, and one alum w. a thicker core. All three I still have, all are fine, and all three have the bung for the Renix temp sensor. I don't know why everyone says "most" HO radiators don't have the bung. I've never seen one that did not have it. :dunno:

[Boots]

So I can completely eliminate the Heater control valve with no side effects, right? I don't need to get a HO thermostat housing but I do need to make sure the radiator has the bung for the temp switch, right? Every thing else seems pretty straight forward now as far as the cooling system swap. For the fan though, any body got a wiring diagram? My dad had a laser temp gun so I'm gonna try comparing that with the dash gauge.

 

Chad,

 

How's life in Aptos? Used

to live there (Freedom Blvd) a great many years ago.

 

I live in Larkin Valley, I guess it's been pretty good.

 

Thanks

Chad

[ParadiseMJ]

So I can completely eliminate the Heater control valve with no side effects, right? I don't need to get a HO thermostat housing but I do need to make sure the radiator has the bung for the temp switch, right? Every thing else seems pretty straight forward now as far as the cooling system swap. For the fan though, any body got a wiring diagram? My dad had a laser temp gun so I'm gonna try comparing that with the dash gauge.

 

I completely eliminated the HCV on my XJ with no problems...A/C works fine. If you eliminate yours and you find that it isn't working like you want it to, you can always put one in with the hoses you have (some cutting required).

 

The fan relay is on the driver's side, top of fender, right behind the EGR solenoid. If you splice a switch wire in to the orange wire, and power the switch, you'll be good. I don't have a wiring diagram

[Boots]

The fan relay is on the driver's side, top of fender, right behind the EGR solenoid. If you splice a switch wire in to the orange wire, and power the switch, you'll be good. I don't have a wiring diagram

 

Mine didn't come with the fan from the factory so I don't have the relay on the drivers side fender. My relay is on the Passenger side fender along with some nasty wiring. I would like to reuse the factory wiring if possible. I'm guessing that there is a wire harness that plugs into this plug that would hook up to the relay, fan, and temp switch????

 

Image Not Found

 

Image Not Found

 

Or is the factory wiring not even going to be there?

 

Thanks

Chad

[Boots]

Bump :wrench: