Need Electrical Help on 84
Thread Starter
Heel & Toe
Joined: May 2004
Posts: 23
Likes: 0
From: Navarre Florida
Need Electrical Help on 84
I have just replaced the engine in my 84 and have some
electrical problems. I was carefull and re-installed the
cable harness as it was. The main thing was the three
grounds at the left rear of the engine. The new engine
starts and runs fine, but the following has appeared.
1. The cooling fan will not run under ECM control. I have
traced the harness and can't find any thing wrong. I
bypassed the ECM - hooked the sensor to the relay and
now that is working.
2. I drained all the gas out of the tank, but it still showed
half a tank.
3. The speedo is not working.
4. The voltmeter seems to read low. 11.2 on fully charged
battery before startup.
Everything work fine before the engine replacement.
I'm guessing that some ground is missing. I have purchased a
shop manual on ebay and it is on the way(that may take a week
for the check to get there and for the manual to get here.
I sure wish someone could scan and send me a electrical diagram
for the 84 as the manual won't get here before the weekend.
If anyone has any ideas, it would sure help. I want to get back
on the stree this weekend if possible.
electrical problems. I was carefull and re-installed the
cable harness as it was. The main thing was the three
grounds at the left rear of the engine. The new engine
starts and runs fine, but the following has appeared.
1. The cooling fan will not run under ECM control. I have
traced the harness and can't find any thing wrong. I
bypassed the ECM - hooked the sensor to the relay and
now that is working.
2. I drained all the gas out of the tank, but it still showed
half a tank.
3. The speedo is not working.
4. The voltmeter seems to read low. 11.2 on fully charged
battery before startup.
Everything work fine before the engine replacement.
I'm guessing that some ground is missing. I have purchased a
shop manual on ebay and it is on the way(that may take a week
for the check to get there and for the manual to get here.
I sure wish someone could scan and send me a electrical diagram
for the 84 as the manual won't get here before the weekend.
If anyone has any ideas, it would sure help. I want to get back
on the stree this weekend if possible.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Paul O
1. The cooling fan will not run under ECM control. I have
traced the harness and can't find any thing wrong. I
bypassed the ECM - hooked the sensor to the relay and
now that is working.
2. I drained all the gas out of the tank, but it still showed
half a tank.
3. The speedo is not working.
4. The voltmeter seems to read low. 11.2 on fully charged
battery before startup.
traced the harness and can't find any thing wrong. I
bypassed the ECM - hooked the sensor to the relay and
now that is working.
2. I drained all the gas out of the tank, but it still showed
half a tank.
3. The speedo is not working.
4. The voltmeter seems to read low. 11.2 on fully charged
battery before startup.
2.) The float for the gauge is probably hung up on some part of the fuel gauge sender/fuel pump assembly. Such problems are common with all C4s. You can pull it out of the tank and check it out, or see if it corrects itself when you refill it.
3.) Makes no sense with nothing more than an engine swap. My first guess is that something got disconnected that didn't need to be.
4.) Sounds like a battery that is ready to be exchanged.
Other than all that, you can make sure all your ground wires are clean and tight. The first ground I would look at, is the negative battery cable, at BOTH ends. It couldn't hurt to run an extra ground strap or two if you sense a deficiency. It isn't possible to over ground anything.
RACE ON!!!
Thread Starter
Heel & Toe
Joined: May 2004
Posts: 23
Likes: 0
From: Navarre Florida
1) Haynes shows the temp sensor going to the EMC and the EMC controlling the fan relay.
That is the only wiring diagram that I have right now. The wire at the sensor and the one
at the relay are different color so I went along with the Haynes diagram.
We checked at the EMC and couldn't find either wire. This support your comment,
but the wire color difference make it confusing.
I hooked a wire onto the sensor wire and connected the other end to
the fan relay.
2) I'll fill her up and see if the float was stuck.
3) I haven't crawled back underneath to see if the connector for the
speedo is loose or disconnected. We left the trans in and didn't disconnect
anything at the trans.
4) The battery is real new. Again I wonder about a missing ground.
I really cleaned the three ground wires that connect to the left rear block
before I attached them and used star washers too boot.
Thanks for the reply. I may know more after I try a few things or when
I get the Shop Manual in the mail.
That is the only wiring diagram that I have right now. The wire at the sensor and the one
at the relay are different color so I went along with the Haynes diagram.
We checked at the EMC and couldn't find either wire. This support your comment,
but the wire color difference make it confusing.
I hooked a wire onto the sensor wire and connected the other end to
the fan relay.
2) I'll fill her up and see if the float was stuck.
3) I haven't crawled back underneath to see if the connector for the
speedo is loose or disconnected. We left the trans in and didn't disconnect
anything at the trans.
4) The battery is real new. Again I wonder about a missing ground.
I really cleaned the three ground wires that connect to the left rear block
before I attached them and used star washers too boot.
Thanks for the reply. I may know more after I try a few things or when
I get the Shop Manual in the mail.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Paul O
1) Haynes shows the temp sensor going to the EMC and the EMC controlling the fan relay.
That is the only wiring diagram that I have right now. The wire at the sensor and the one
at the relay are different color so I went along with the Haynes diagram.
We checked at the EMC and couldn't find either wire. This support your comment,
but the wire color difference make it confusing.
I hooked a wire onto the sensor wire and connected the other end to
the fan relay.
That is the only wiring diagram that I have right now. The wire at the sensor and the one
at the relay are different color so I went along with the Haynes diagram.
We checked at the EMC and couldn't find either wire. This support your comment,
but the wire color difference make it confusing.
I hooked a wire onto the sensor wire and connected the other end to
the fan relay.
The wire for circuit# 335 is brown at the fan switch in the head. It runs through a connector or two and is, dark green/white, at terminal "B" of the fan relay.
RACE ON!!!
Intermediate
Joined: Nov 2005
Posts: 46
Likes: 0
From: Cumming GA
Originally Posted by CFI-EFI
Does it ever get chilly in Navarre? Next time it does, take a match to that Haynes, and use it to keep yourself warm. It will be MUCH more effective at keeping you warm, than supplying you with accurate information. To test your fan, simply remove the wire from the switch, and ground it. That is what the switch does.
The wire for circuit# 335 is brown at the fan switch in the head. It runs through a connector or two and is, dark green/white, at terminal "B" of the fan relay.
RACE ON!!!
The wire for circuit# 335 is brown at the fan switch in the head. It runs through a connector or two and is, dark green/white, at terminal "B" of the fan relay.
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
You aren't confusing the refrigerant pressure switch at the A/C compressor for the ECM, are you? What is the circuit number? I'll trace it AGAIN in my Helms. I'm never too old to learn.
RACE ON!!!
PS. I hope you realize the degree to which I am restraining myself.
RACE ON!!!
PS. I hope you realize the degree to which I am restraining myself.
Thread Starter
Heel & Toe
Joined: May 2004
Posts: 23
Likes: 0
From: Navarre Florida
It does get cool here. We have had frost a couple of times in the last
few weeks. It sure is alot better here than where I moved from - the Chicagoland area.
I don't know the circuit number but agree about using the Haynes as a fire starter.
Chiltons is not much better.
I recheck and the A/C does run a circuit through the EMC that comes out to control the fan.
It shows this on page 3-5. I check for continuity between the sensor and the
B terminal on the relay. No continuity. We had first tried shorting the
sensor to ground. The jumper wire did the trick. We also pulled the wiring
harness out as much as possible to trace it. Didn't see anything wrong there or
any connectors. Hopefully the wiring diagram in the Shop Manual will shed
some light on this.
Haynes and Chiltons gives you just enough info to get you confused or in trouble.
Thanks for your replies. At least I know I'm not alone in being confused
about what is what.
few weeks. It sure is alot better here than where I moved from - the Chicagoland area.
I don't know the circuit number but agree about using the Haynes as a fire starter.
Chiltons is not much better.
I recheck and the A/C does run a circuit through the EMC that comes out to control the fan.
It shows this on page 3-5. I check for continuity between the sensor and the
B terminal on the relay. No continuity. We had first tried shorting the
sensor to ground. The jumper wire did the trick. We also pulled the wiring
harness out as much as possible to trace it. Didn't see anything wrong there or
any connectors. Hopefully the wiring diagram in the Shop Manual will shed
some light on this.
Haynes and Chiltons gives you just enough info to get you confused or in trouble.
Thanks for your replies. At least I know I'm not alone in being confused
about what is what.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Measure the battery voltage with a voltmeter and compare it to the dash voltmeter. Most likely the dash voltmeter is out of calibration or needs repair.
CFI, I am so proud of you for holding it all in........
CFI, I am so proud of you for holding it all in........
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Intermediate
Joined: Nov 2005
Posts: 46
Likes: 0
From: Cumming GA
Originally Posted by CFI-EFI
You aren't confusing the refrigerant pressure switch at the A/C compressor for the ECM, are you? What is the circuit number? I'll trace it AGAIN in my Helms. I'm never too old to learn.
RACE ON!!!
PS. I hope you realize the degree to which I am restraining myself.
RACE ON!!!
PS. I hope you realize the degree to which I am restraining myself.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Paul O
I recheck and the A/C does run a circuit through the EMC that comes out to control the fan.
It shows this on page 3-5.
It shows this on page 3-5.
Originally Posted by Paul O
I check for continuity between the sensor and the
B terminal on the relay. No continuity.
B terminal on the relay. No continuity.
Originally Posted by Paul O
We had first tried shorting the
sensor to ground. The jumper wire did the trick.
sensor to ground. The jumper wire did the trick.
Originally Posted by Paul O
Thanks for your replies. At least I know I'm not alone in being confused
about what is what.
about what is what.
RACE ON!!!
Thread Starter
Heel & Toe
Joined: May 2004
Posts: 23
Likes: 0
From: Navarre Florida
Page 3-5 shows the basic circuit in my version of the Haynes manual (Haynes # 24041 printed in 1999). The sensor (switch) does connect to
ground when the temperature is reached (it a simple themo switch). I
believe that the wire runs to the EMC and then connects with the EMC
output (controlled via the A/C) and then runs to the fan relay. The jumper
wire connects the switch (which is open until the temperature is reached) to the wire running to the fan relay. This bypasses the wires
running to and from the EMC. This is where I think there is a missing connection. My background is in electronic and software engineering so
I understand circuitry.
About being new - I've had this car since 2000 and put about 35K miles on it. I know if fairly well. As for me, I'm about 6 years from Social Security Retirement and have built many strip and street racing machines from a wheel standing 55 Chevy to a sub 11 second pickup.
My logon here is new. I have been a member since 2000, but when I
moved I lost my password. With a new email address, I couldn't get to
my old profile or have my password sent to me, so I had to re-up.
I do appreciate the replies and find them informative and entertaining.
Thanks again.
ground when the temperature is reached (it a simple themo switch). I
believe that the wire runs to the EMC and then connects with the EMC
output (controlled via the A/C) and then runs to the fan relay. The jumper
wire connects the switch (which is open until the temperature is reached) to the wire running to the fan relay. This bypasses the wires
running to and from the EMC. This is where I think there is a missing connection. My background is in electronic and software engineering so
I understand circuitry.
About being new - I've had this car since 2000 and put about 35K miles on it. I know if fairly well. As for me, I'm about 6 years from Social Security Retirement and have built many strip and street racing machines from a wheel standing 55 Chevy to a sub 11 second pickup.
My logon here is new. I have been a member since 2000, but when I
moved I lost my password. With a new email address, I couldn't get to
my old profile or have my password sent to me, so I had to re-up.
I do appreciate the replies and find them informative and entertaining.
Thanks again.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Paul O
Page 3-5 shows the basic circuit in my version of the Haynes manual (Haynes # 24041 printed in 1999).
Originally Posted by Paul O
The sensor (switch) does connect to
ground when the temperature is reached (it a simple themo switch). I
believe that the wire runs to the EMC and then connects with the EMC
output (controlled via the A/C) and then runs to the fan relay.
ground when the temperature is reached (it a simple themo switch). I
believe that the wire runs to the EMC and then connects with the EMC
output (controlled via the A/C) and then runs to the fan relay.
Originally Posted by Paul O
The jumper wire connects the switch (which is open until the temperature is reached) to the wire running to the fan relay. This bypasses the wires running to and from the EMC. This is where I think there is a missing connection.
RACE ON!!!
Navigator
Joined: Jan 2006
Posts: 9
Likes: 0
Just my two cents
I also have an 84 that has just had the engine replaced. Along with other problems the cooling fan ran all the time. I assumed a stuck relay or somthing of that sort was my problem. After a good deal of time I discovered that when the engine was reinstalled, (without trans. )removal that the wire from the temp sensor to the relay was pinched between the trans. and the engine block. I ran a secondary wire in its place and everything works great. Where my situation resulted in a grounded wire yours could be an open. Worth a look anyway.Good Luck
