I have a 88' chevy beretta the cooling fan is not working. Fan is good how do I check fan relay and sensor that control that? Thanks

mhunike
10

Asked by mhunike Nov 14, 2012 at 11:29 AM about the 1988 Chevrolet Beretta

Question type: Maintenance & Repair

24 Answers

John Saffrahn
15,245

Jump the connectors on the aldl that make the check engine light flash to pull codes and see if the cooling fan comes on.

mhunike
10

Yes I jumpered out the aldl and the fan came on.

John Saffrahn
15,245

I had a friend with this issue and I spent over 3 hours testing and testing and never got anywhere. Finally I said F*** it and wired in a switch to activate the relay so he could control the fans. The only time it will ever overheat is when you are sitting still so if he ever gets into a traffic jam or has to sit at a long light he turns it on. Other than that he never has to use it. The two main things that control the fans are engine temp and vehicle speed and they both worked fine. I was baffled, sorry I can't help much.

Tom Torres
1,555

unplug coolant temp sensor on left side of engine and jump the gray and gry/red tracer wires together if fan turns on it needs a sensor if not further tests need to be done if u used the ALDL connector to test it and the fan kicked on the fan, relay, and wires are good going out of the computer

mhunike
10

Well Tom I went and jumped gray/red and gray wires from coolant sensor conn. I cut ignition to on fan didn't come on. I did not start engine. Yes the fan came on when I jumper ALDL and cut ignition on. I guess I will have to trace wires to computer. Do you know what pins those two wires would be on? That is interesting about how coolant sensor works when it satisfied it shorts out sending signal to computer. I guess If I found out that the wires are good to computer then I have a problem in computer circuit? It not signaling to ouput circuit. Thanks for the help I like to learn.

Tom Torres
1,555

with the key on unplug the sensor and measure the gray wire for voltage should have 5 volts and gray and red wire for ground (one meter lead to battery positive the other to the wire) if u have battery voltage u have a good ground if ur missing one of those then go to computer let me know what u find and we will go from there

John Saffrahn
15,245

I take it you don't have a temp gauge?

Tom Torres
1,555

what size engine do u have and as john said does temp guage function

mhunike
10

Yes I have temperature gauge not light. It's a 2.0l 4 cylinder. When fan was working right needle on gauge got to middle where square is, the fan would come on. Now gauge just goes pass square and moves toward Hot. I have let the engine run intill needle was in between middle and hot thinking fan might come on but never did, shut engine down. I checked measurements. Gray wire to battery gnd or frame gnd 5Vdc. Gray/ red to + battery 0Vdc. Is that how you wanted me to check wiring?

John Saffrahn
15,245

Same thing was going on with his. Sometimes a vehicle can have 2 engine coolant temp sensors one for the gauge and the other for the ecm but his only had one. The switch was simple, if you're interested all you need is a 10 amp switch and some 16 gauge wire. Find the spot in the fuse box for the fan relay and test the holes for relay prong numbers 85&86 one will have 12V and the other should have a ground but won't. Attach one end of the wire to the side that is supposed to have a ground and the other end of the wired switch to a ground. If you need a pic I can draw one up.

Tom Torres
1,555

okay and yes it is the right way if u got 0 v on gray/red i thinking there is an open in the wire to the comuter is the sensor a 2 wire or 3 wire? john is right there are two sensors if it has 3 wires both are built into one if 2 wires than there is another sensor according to my information, the two sensors or in the same place okay back to the wire with 0v on it (the gry/rd wire) that should read battery voltage the way u tested it so at the computer on connector 2 position b6 is a purple wire that is the ground for that wire and there is a splice in the wire that branches off to other various places thats y it goes from ppl to gry/rd in color measure for gound there if u do have a gound there u have a break in wire and start to look for splice in wire

mhunike
10

Yes I have two sensor on right side one on top of the other facing the front of car. The coolant sender is a one wire. Now I want to make sure I have this right. The gry /red wire is suppose to have battery voltage with ignition on one lead to wire and other to + battery? And you want to me go to computer find conn. 2 postion b6 which is purple which is gnd then back track wire intill I find gry/red then measure to gnd? If that the case couldn't I just ohn wire from gry/red to purple at computer? I know it will be a long jumper . If it open then wire is broke will have to replace wire.

Tom Torres
1,555

right yes you can ohm the wire im thinking since that wire splices of to other grounds you would be having more problems than just a inoperative cooling fan that ppl wire supplies ground to other sensor so you would have to find that break in the wire so u dont cut the part of wire that connects the other sensor to that ground if that makes sense also for that other senser i believe it is a dk grn wire with key on ground that out to see if fan operates if it does replace that sender and a test warm up to see if it fixed it

mhunike
10

yes I think your right about coolant gauge sender I believe it is dk grn. Ok if key is on you want me to unplug dk grn wire jumper it to gnd or leave wire on sensor and jumper to gnd to see if fan comes on?

Tom Torres
1,555

you can unplug it

Best Answer
mhunike
10

No it didn't work I unplugged sender put jumper from drk grn to gnd. I will ohm out gry/ red to purple if it not there I will look for the split.

mhunike
10

Tom you are going to hurt me. I went out and meaure voltages again on gry/ red wire to + battery and I am getting battery voltage I still have 5vdc on gry wire. I moved wire to see if I could get it to 0 out. Still holding battery voltaged. I know that I was measuring right the first time when I got 0 vdc. Now I did unplug that sender drk grn wire I wonder if that had something to do with it? Do you think that drk grn and gry/red are tie together with purple?

Tom Torres
1,555

so u measure 12 v on the gry red wire when the sender was unplugged or still plugged in? according to my info the sender is for the gauge hot temp light so they r seprete they could be shorted together

mhunike
10

Hi Tom Happy Thankgiving. when I check drk grn wire and found out that fan didn't cut on I decided to check gry/red wire again. That when I saw battery voltage. I plugged back the drk grn and I am still getting 12vdc on gry/red. Just fofr kicks I guess I will run car and see if fan cut on. I know it not going to fix itself I still think it's in wiring.

Tom Torres
1,555

same to u too. im thinking so too

mhunike
10

Good morning Looked a car alittle yesterday. Cranked it up it started to go to hot again. I pulled temperature sensor off gry & gry/red wires the fan came on. I believe I tried thisbefore I talked to you guys and the fan never came on so something has changed. Now I did it a few times. The next time I unplugged I waited for fan to cut on then connected it back. well when the gauge got back to below square the fan cut off. I will tell you that I did replace the temp. sensor before I got up with you guys. I know you will say you need to try another sensor. My thing is it knew how to cut it off. it just doesn't know how to cut it on.I wonder if I could meter sensor when it gets to where fan is suppose to cut on to see what it reads but by unplugging conn the circuit is showing open making the ouput cut on for fan to cut on. Thanks

Tom Torres
1,555

you have to back probe the wire while coonnected to sensor use something small like a needle slide it in to the back of that connector going parrallel with the wire

mhunike
10

I hooked up meter to coolant sensor put pins in back of conn. I notice when I hooked up meter it was set up on ohms scale that I was getting a reading. When I started engine, circuit opened up could not read anything in ohms. The repair book says thermresistor which varies the value of the voltage output accordance to the temperature. If this is a resistor why wouldn't I beable to see a resistance value while the car is running? Does it work that way? I hooked up meter gry wire and other lead to - on battery. I got 1.7 vdc and it was dropping as the car got hotter. It got down to 1.5vdc but nothing happening had to cut fan on. I also metered gray/red to +battery got battery voltage. I did find though when I shorted pins together that it sent a signal to cut fan on. So if you open or close circuit fan comes on. I did not see any difference on meter when the motor was satified and fan cut off. I am up for any ideas. I am thinking of unhooking battery clearing everything out and see what that does.

Tom Torres
1,555

if u jumpered the two terminals together and fans turned on than id replace the sensor and also alot of the tests u did wre pointless and not needed the temp sensor is skewed if u remember i told u to jumper the wires together before to see if fan kicks on and it did not work that was because that wire was not getting a ground now that it is now it turned the fan on hope that makes sense and let me know how it goes

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