Temp guage and electic fan sending unit.

Javelin3o4 · 05-29-2008, 11:34:38 PM

I have Auto Lite gauges in my car and I also put an electric fan w/ the summit 185/180 on/off relay kit. I put the sensor in the cyliner head and ran the wire from the relay to the sending unit and also connected my autometer gauge to it aswell.

The problem im having is the needle is constantly pegged. Are you supposed to run 2 differnet sensors? 1 for the fan relay and 1 for the temp sender unit? With the guage pegged the fan comes on as soon as the ignition is turned cause i guess because the needle is pegged over 200 degrees.

If I have to run both where would you guys suggest the one for the fan goes? Stay in the cyliner head and put the temp gauges sending unit on the intake?

heavy duty · 05-30-2008, 12:05:29 PM

I used a seperate sending unit for each. One for the fan one for the gauge

mercurytech · 05-30-2008, 12:26:51 PM

I installed the temp switch for electric fans in the passenger side head where the block plug was installed. Installed the temp sender for gauge where the original one was installed on the driver's side head. I also have A/C, so I installed a diode in the power lead to the fans to keep the current from "back flowing" to the relay when the A/C is turned on.

BonzoHansen · 05-30-2008, 02:17:10 PM

Common GM OE location:

Fan SWITCH - RH head
Coolant Temp Sensor - LH head.

Yes, the 2 parts are different (if I read the question right)

I have used a t-stat housing mounted fan switch with excellent results.

ULTM8Z · 06-05-2008, 04:27:13 PM

Sounds like you hooked up a gauge to a temperature switch. That's a problem right there. A gauge won't run off a temperature switch.

Also that temp switch supplies the switchable ground connection to the fan relay. Since you have the gauge and the fan wired in parallel, the relay may be picking up a sneak path to ground through the autometer gauge and which is then turning the relay on, effectively bypassing the temp swich altogether. That would explain why your fans are constantly on.

You have to get a dedicated temperature sending unit for a dashboard gauge. The temp switch you have now is only for the fans.

Javelin3o4 · 06-05-2008, 04:44:04 PM

yeah thats what i figured, now i gotta figure out where i should mount the sending units, cause it appears i only have 2 choices, drivers side head, and intake. Just need to decide which one goes where.

ULTM8Z · 06-05-2008, 05:26:13 PM

Quote:

Originally Posted by Javelin3o4

yeah thats what i figured, now i gotta figure out where i should mount the sending units, cause it appears i only have 2 choices, drivers side head, and intake. Just need to decide which one goes where.

In reality, it doesn't really matter too much. Yeah, the intake location may be slightly warmer than the head location, but in the end, both the gauge and the fan will operate just fine in either location.

old zeder · 06-05-2008, 07:07:01 PM

I just installed a set of electric fans and put the temp switch in the driver side head as someone here sent me a very good data sheet that said the temp in the heads is a little higher due to cylinder location, and the gauge temp sender in the manifold, fans are working in the temp range they were set for on at 180 deg. off at 165 - 170 deg.

Javelin3o4 · 06-05-2008, 11:09:19 PM

well i got the temp sender and the temp switch installed. Switch in drivers side head, temp sender in the intake, however the fan still comes on when the ignition is turned on which makes me think either something is wrong with the temp switch or the relay.

ULTM8Z · 06-05-2008, 11:53:34 PM

Quote:

Originally Posted by Javelin3o4

well i got the temp sender and the temp switch installed. Switch in drivers side head, temp sender in the intake, however the fan still comes on when the ignition is turned on which makes me think either something is wrong with the temp switch or the relay.

Ok, couple of things.

If the engine is cold, take an ohm meter and touch the center terminal of the switch with one probe and the body of the switch with the other probe. If you get continuity, you have a bad switch.

The other thing I can think of is that you miswired your relay. Assuming you have the typical 30 amp relay...

You want to the battery hooked up to terminal 30, the fan motor hot lead hooked up to terminal 87, and then a 12V switched ignition source to 85 and the temp switch hooked up to 86. 85 and 86 can be reversed and 30 and 87 can be reversed. But the partitioning has to be this way or the circuit won't work properly. The ground lead on the fan motor goes directly to chassis ground. You shouldn't have anything hooked up to terminal 87A.

What I'm thinking is that you wired the relay such that the 12V switched ignition is feeding the fan motor.

You can also check the relay itself to see if it's good. Disconnect the relay from everything, then take an ohm meter across terminals 30 and 87. It should read open (no continuity). Then take 86 and connect it to ground and take a 12V source and connect it to 85. You should hear a click. At that point, repeat the ohm meter test and it should read close to zero ohms.

Javelin3o4 · 06-06-2008, 12:32:18 AM

here is the pdf for the instructions on the kit i recieved from summit. I wired up, like it shows.

http://static.summitracing.com/globa...sum-890015.pdf

I put my DMM on the tab for the wire of the thermal switch then touched the outside threaded portion of the body of the switch and it got continuity.

ULTM8Z · 06-06-2008, 12:34:28 AM

Quote:

Originally Posted by Javelin3o4

here is the pdf for the instructions on the kit i recieved from summit. I wired up, like it shows.

http://static.summitracing.com/globa...sum-890015.pdf

I put my DMM on the tab for the wire of the thermal switch then touched the outside threaded portion of the body of the switch and it got continuity.

If you're getting continuity like that with a switch at or near room temperature, the switch is bad. Out of curiosity, are you getting close to zero ohms, or some higher resistance. Curious if somehow you got hold of a sender and not a switch. A sender would still complete the circuit and run the fans at room temperature.

Unfortunately that pdf doesn't really tell me anything about the relay. They must have a harness pre-built for it and are simply telling what color wires go where.

Javelin3o4 · 06-06-2008, 12:41:40 AM

the engine is cold cause it hasnt been started in a few days. the switch has the 185/170 stamped onto the the housing. I'll take a look again and see what the actual cont. reading is.

Marks71BB · 06-06-2008, 12:50:34 AM

If you got continuity with the engine cold did you try it hot and see if the circuit is then open? Just curious if the temp switch is normaly closed. Otherwise its bad and ya need a new one.

Javelin3o4 · 06-06-2008, 01:04:34 AM

didnt try it when its hot, only cause its late and dont think my neighbors would appreciate open headers at this time a night. The fan does not come on if i disconnect the wire at the termal switch so, im thinking it may be an issue with the thermal switch, cause i've checked my connections and they appear to be correct. unless the relay is the issue.